Current inhibition of human EAG1 potassium channels by the Ca binding protein S100B

Voltage-dependent human ether à go-go (hEAG1) potassium channels are implicated in neuronal signaling as well as in cancer cell proliferation. Unique sensitivity of the channel to intracellular Ca²⁺ is mediated by calmodulin (CaM) binding to the intracellular N- and C-termini of the channel. Here we show that application of the acidic calcium-binding protein S100B to inside-out patches of Xenopus oocytes causes Ca²⁺-dependent inhibition of expressed hEAG1 channels. Protein pull-down assays and fluorescence correlation spectroscopy (FCS) revealed that S100B binds to hEAG1 and shares the same binding sites with CaM. Thus, S100B is a potential alternative calcium sensor for hEAG1 potassium channels.

Structured summary

MINT-7988123: CaM (uniprotkb:P62158) and EAG1 alpha (uniprotkb:O95259) physically interact (MI:0915) by competition binding (MI:0405)MINT-7988019, MINT-7988052: EAG1 alpha (uniprotkb:O95259) binds (MI:0407) to s100B (uniprotkb:P02638) by pull down (MI:0096)MINT-7988074: EAG1 alpha (uniprotkb:O95259) and s100B (uniprotkb:P02638) physically interact (MI:0915) by competition binding (MI:0405)MINT-7988100:CaM (uniprotkb:P62158) and EAG1 alpha (uniprotkb:O95259) bind (MI:0407) by fluorescence correlation spectroscopy (MI:0052).     

S100 proteins interact with the N-terminal domain of MDM2

S100 proteins interact with the transactivation domain and the C-terminus of p53. Further, S100B has been shown to interact with MDM2, a central negative regulator of p53. Here, we show that S100B bound directly to the folded N-terminal domain of MDM2 (residues 2-125) by size exclusion chromatography and surface plasmon resonance experiments. This interaction with MDM2 (2-125) is a general feature of S100 proteins; S100A1, S100A2, S100A4 and S100A6 also interact with MDM2 (2-125). These interactions with S100 proteins do not result in a ternary complex with MDM2 (2-125) and p53. Instead, we observe the ability of a subset of S100 proteins to disrupt the extent of MDM2-mediated p53 ubiquitylation in vitro.

Structured summary

MINT-7905256: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A6 (uniprotkb:P06703) by surface plasmon resonance (MI:0107)MINT-7905063: MDM2 (uniprotkb:Q00987) and s100A1 (uniprotkb:P23297) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905376: s100A4 (uniprotkb:P26447) and MDM2 (uniprotkb:Q00987) physically interact (MI:0915) by competition binding (MI:0405)MINT-7905130: s100A6 (uniprotkb:P06703) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905207: s100A6 (uniprotkb:P06703) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905043: s100B (uniprotkb:P04271) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905196: p53 (uniprotkb:P04637) and s100A4 (uniprotkb:P26447) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905358: p53 (uniprotkb:P04637) and s100A4 (uniprotkb:P26447) physically interact (MI:0915) by fluorescence polarization spectroscopy (MI:0053)MINT-7905220: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100B (uniprotkb:P04271) by surface plasmon resonance (MI:0107)MINT-7905104: s100A4 (uniprotkb:P26447) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905229: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A1 (uniprotkb:P23297) by surface plasmon resonance (MI:0107)MINT-7905317, MINT-7905162: s100B (uniprotkb:P04271) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905238: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A2 (uniprotkb:P29034) by surface plasmon resonance (MI:0107)MINT-7905174, MINT-7905308: s100A1 (uniprotkb:P23297) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905247: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A4 (uniprotkb:P26447) by surface plasmon resonance (MI:0107)MINT-7905090: s100A2 (uniprotkb:P29034) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905142, MINT-7905326: MDM2 (uniprotkb:Q00987) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905185, MINT-7905347: s100A2 (uniprotkb:P29034) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)     

An S-locus receptor-like kinase in plasma membrane interacts with calmodulin in Arabidopsis

Calmodulin-regulated protein phosphorylation plays a pivotal role in amplifying and diversifying the action of calcium ion. In this study, we identified a calmodulin-binding receptor-like protein kinase (CBRLK1) that was classified into an S-locus RLK family. The plasma membrane localization was determined by the localization of CBRLK1 tagged with a green fluorescence protein. Calmodulin bound specifically to a Ca²⁺-dependent calmodulin binding domain in the C-terminus of CBRLK1. The bacterially expressed CBRLK1 kinase domain could autophosphorylate and phosphorylates general kinase substrates, such as myelin basic proteins. The autophosphorylation sites of CBRLK1 were identified by mass spectrometric analysis of phosphopeptides.

Structured summary

MINT-6800947:CBRLK1 (uniprotkb:Q9ZT06) and AtCaM2 (uniprotkb:P25069) bind (MI:0407) by electrophoretic mobility shift assay (MI:0413)MINT-6800966:AtCaM2 (uniprotkb:P25069) and CBRLK1 (uniprotkb:Q9ZT06) bind (MI:0407) by competition binding (MI:0405)MINT-6800930:CBRLK1 (uniprotkb:Q9ZT06) binds (MI:0407) to AtCaM2 (uniprotkb:P25069) by far Western blotting (MI:0047)MINT-6800978:AtCaM2 (uniprotkb:P25069) physically interacts (MI:0218) with CBRLK1 (uniprotkb:Q9ZT06) by cytoplasmic complementation assay (MI:0228)     

A scanning peptide array approach uncovers association sites within the JNK/βarrestin signalling complex

βarrestins are molecular scaffolds that can bring together three-component mitogen-activated protein kinase signalling modules to promote signal compartmentalisation. We use peptide array technology to define novel interfaces between components within the c-Jun N-terminal kinase (JNK)/βarrestin signalling complex. We show that βarrestin 1 and βarrestin 2 associate with JNK3 via the kinase N-terminal domain in a region that, surprisingly, does not harbour a known ‘common docking’ motif. In the N-domain and C-terminus of βarrestin 1 and βarrestin 2 we identify two novel apoptosis signal-regulating kinase 1 binding sites and in the N-domain of the βarrestin 1 and βarrestin 2 we identify a novel MKK4 docking site.

Structured summary

MINT-7263196, MINT-7263175: Arrestin beta-2 (uniprotkb:P32121) binds (MI:0407) to ASK1 (uniprotkb:Q99683) by peptide array (MI:0081)MINT-7263136: JNK3 (uniprotkb:P53779) binds (MI:0407) to Arrestin beta-1 (uniprotkb:P49407) by peptide array (MI:0081)MINT-7263161: JNK3 (uniprotkb:P53779) binds (MI:0407) to Arrestin beta-2 (uniprotkb:P32121) by peptide array (MI:0081)MINT-7263304: Arrestin beta-1 (uniprotkb:P49407) physically interacts (MI:0915) with ASK1 (uniprotkb:Q99683) by anti tag coimmunoprecipitation (MI:0007)MINT-7263286: Arrestin beta-2 (uniprotkb:P32121) binds (MI:0407) to MKK4 (uniprotkb:P45985) by peptide array (MI:0081)MINT-7263231, MINT-7263254: Arrestin beta-1 (uniprotkb:P49407) binds (MI:0407) to ASK1 (uniprotkb:Q99683) by peptide array (MI:0081)MINT-7263269: Arrestin beta-1 (uniprotkb:P49407) binds (MI:0407) to MKK4 (uniprotkb:P45985) by peptide array (MI:0081)     

S100 proteins regulate the interaction of Hsp90 with Cyclophilin 40 and FKBP52 through their tetratricopeptide repeats

S100 proteins are a subfamily of the EF-hand type calcium sensing proteins, the exact biological functions of which have not been clarified yet. In this work, we have identified Cyclophilin 40 (CyP40) and FKBP52 (called immunophilins) as novel targets of S100 proteins. These immunophilins contain a tetratricopeptide repeat (TPR) domain for Hsp90 binding. Using glutathione-S transferase pull-down assays and immunoprecipitation, we have demonstrated that S100A1 and S100A2 specifically interact with the TPR domains of FKBP52 and CyP40 in a Ca²⁺-dependent manner, and lead to inhibition of the CyP40-Hsp90 and FKBP52-Hsp90 interactions. These findings have suggested that the Ca²⁺/S100 proteins are TPR-targeting regulators of the immunophilins-Hsp90 complex formations.

Structured summary

MINT-7710442: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by competition binding (MI:0405)MINT-7710192: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A1 (uniprotkb:P35467) by pull down (MI:0096)MINT-7710412: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by competition binding (MI:0405)MINT-7710374: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-7710452: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with S100A2 (uniprotkb:P29034) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007)MINT-7710387: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A6 (uniprotkb:P06703) by pull down (MI:0096)MINT-7710279: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A1 (uniprotkb:P35467) by competition binding (MI:0405)MINT-7710224: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to Hsp90 (uniprotkb:P07900) by pull down (MI:0096)MINT-7710464: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with S100A6 (uniprotkb:P06703) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007)MINT-7710249: Cyp40 (uniprotkb:P26882) binds (MI:0407) to Hsp90 (uniprotkb:P07900) by pull down (MI:0096)MINT-7710422: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by competition binding (MI:0405)MINT-7710348: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-7710208: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A1 (uniprotkb:P35467) by pull down (MI:0096)MINT-7710265: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A1 (uniprotkb:P35467) by competition binding (MI:0405)MINT-7710361: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A6 (uniprotkb:P06703) by pull down (MI:0096)MINT-7710476: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A2 (uniprotkb:P29034) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007)MINT-7710316: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A1 (uniprotkb:P35467) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007)MINT-7710432: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by competition binding (MI:0405)MINT-7710488: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A6 (uniprotkb:P06703) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007)MINT-7710329: S100A6 (uniprotkb:P14069) physically interacts (MI:0914) with FKBP52 (uniprotkb:P30416) and Cyp40 (uniprotkb:Q08752) by anti bait coimmunoprecipitation (MI:0006)MINT-7710295: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with Hsp90 (uniprotkb:P07900) and S100A1 (uniprotkb:P35467) by anti tag coimmunoprecipitation (MI:0007)     

Importin β3 mediates the nuclear import of human ribosomal protein L7 through its interaction with the multifaceted basic clusters of L7

We show that importin β3 is essential for the nuclear import of L7. The import is mediated via the multifaceted basic amino acid clusters present in the NH₂-region of L7, and is RanGTP-dependent. Using a (EGFP)₃ reporter system and a FRAP assay, the role the individual clusters play as a functional NLS has been characterized, and each cluster was found to exhibit a different rate of real time nuclear uptake. We assume that having such a multiple NLS may provide L7 with preferential nuclear uptake.

Structured summary

MINT-7992735: Importin beta-3 (uniprotkb:O00410) binds (MI:0407) to L7 (uniprotkb:P18124) by biophysical (MI:0013)MINT-7992687: L7 (uniprotkb:P18124) binds (MI:0407) to Importin beta-3 (uniprotkb:O00410) by filter binding (MI:0049)MINT-7992699: L7 (uniprotkb:P18124) physically interacts (MI:0915) with Importin beta-3 (uniprotkb:O00410) by affinity chromatography technology (MI:0004)MINT-7992718: L7 (uniprotkb:P18124) physically interacts (MI:0915) with RAN (uniprotkb:P62826) by competition binding (MI:0405)MINT-7992671: L7 (uniprotkb:P18124) physically interacts (MI:0915) with Importin beta-3 (uniprotkb:O00410) by pull down (MI:0096)     

Isolation of a point-mutated p47 lacking binding affinity to p97ATPase

p47, a p97-binding protein, functions in Golgi membrane fusion together with p97 and VCIP135, another p97-binding protein. We have succeeded in creating p47 with a point mutation, F253S, which lacks p97-binding affinity. p47 mapping experiments revealed that p47 had two p97-binding regions and the F253S mutation occurred in the first p97-binding site. p47(F253S) could not form a complex with p97 and did not caused any cisternal regrowth in an in vitro Golgi reassembly assay. In addition, mutation corresponding to the p47 F253S mutation in p37 and ufd1 also abolished their binding ability to p97.

Structured summary

MINT-7987189, MINT-7987207, MINT-7987303: p47 (uniprotkb:O35987) binds (MI:0407) to p97 (uniprotkb:Q01853) by pull down (MI:0096)MINT-7987226: p97 (uniprotkb:P46462) binds (MI:0407) to p47 (uniprotkb:O35987) by pull down (MI:0096)MINT-7987348: p97 (uniprotkb:P46462) physically interacts (MI:0915) with Ufd1 (uniprotkb:P70362) by pull down (MI:0096)MINT-7987264: p97 (uniprotkb:P46462) and p47 (uniprotkb:O35987) bind (MI:0407) by competition binding (MI:0405)MINT-7987326: p97 (uniprotkb:P46462) binds (MI:0407) to p37 (uniprotkb:Q0KL01) by pull down (MI:0096)     

Abi1/Hssh3bp1 pY213 links Abl kinase signaling to p85 regulatory subunit of PI-3 kinase in regulation of macropinocytosis in LNCaP cells

Macropinocytosis is regulated by Abl kinase via an unknown mechanism. We previously demonstrated that Abl kinase activity is, itself, regulated by Abi1 subsequent to Abl kinase phosphorylation of Abi1 tyrosine 213 (pY213) [1]. Here we show that blocking phosphorylation of Y213 abrogated the ability of Abl to regulate macropinocytosis, implicating Abi1 pY213 as a key regulator of macropinocytosis. Results from screening the human SH2 domain library and mapping the interaction site between Abi1 and the p85 regulatory domain of PI-3 kinase, coupled with data from cells transfected with loss-of-function p85 mutants, support the hypothesis that macropinocytosis is regulated by interactions between Abi1 pY213 and the C-terminal SH2 domain of p85—thereby linking Abl kinase signaling to p85-dependent regulation of macropinocytosis.

Structured summary

MINT-7908602: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to SHIP2 (uniprotkb:O15357) by array technology (MI:0008)MINT-7908362: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Emt (uniprotkb:Q08881) by array technology (MI:0008)MINT-7908235: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Lyn (uniprotkb:P07948) by array technology (MI:0008)MINT-7908075: Abi1 (uniprotkb:Q8IZP0)binds (MI:0407) to Fgr (uniprotkb:P09769) by array technology (MI:0008)MINT-7908330, MINT-7908522: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Vav1 (uniprotkb:P15498) by array technology (MI:0008)MINT-7907962: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Fyn (uniprotkb:P06241) by array technology (MI:0008)MINT-7908203: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Src (uniprotkb:P12931) by array technology (MI:0008)MINT-7908570: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to SHP-2 (uniprotkb:P35235) by array technology (MI:0008)MINT-7908187, MINT-7908586: Abi1(uniprotkb:Q8IZP0) binds (MI:0407) to Gap (uniprotkb:P20936) by array technology (MI:0008)MINT-7907981, MINT-7907995: Abi1 (uniprotkb:Q8IZP0) physically interacts (MI:0915) with p85a (uniprotkb:P26450) by anti tag coimmunoprecipitation (MI:0007)MINT-7908251: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to PLCG1 (uniprotkb:P19174) by array technology (MI:0008)MINT-7908346: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Grb2 (uniprotkb:P62993) by array technology (MI:0008)MINT-7907945: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Abl (uniprotkb:P00519) by array technology (MI:0008)MINT-7908474: Abi1 (uniprotkb:Q8IZP0)binds (MI:0407) to p85b (uniprotkb:O00459) by array technology (MI:0008)MINT-7908107: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Hck (uniprotkb:P08631) by array technology (MI:0008)MINT-7908011: p85a (uniprotkb:P26450) physically interacts (MI:0915) with Abi1 (uniprotkb:Q8IZP0) by pull down (MI:0096)MINT-7908155: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to FynT (uniprotkb:P06241-2) by array technology (MI:0008)MINT-7908283, MINT-7908490: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to p55g (uniprotkb:Q92569) by array technology (MI:0008)MINT-7907929, MINT-7907815, MINT-7907832, MINT-7907865, MINT-7907897, MINT-7907913, MINT-7907881, MINT-7907848: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to p85a (uniprotkb:P27986) by array technology (MI:0008)MINT-7908059: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Frk (uniprotkb:P42685) by array technology (MI:0008)MINT-7908378: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to CblC (uniprotkb:Q9ULV8) by array technology (MI:0008)MINT-7908618: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to CblA (uniprotkb:B5MC15) by array technology (MI:0008)MINT-7908139, MINT-7908538: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Nap4 (uniprotkb:O14512) by array technology (MI:0008)MINT-7908426: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to CblB (uniprotkb:Q13191) by array technology (MI:0008)MINT-7908506: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Crk (uniprotkb:P46108) by array technology (MI:0008)MINT-7908554: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to mAbl (uniprotkb:P00520) by array technology (MI:0008)MINT-7908043, MINT-7908394: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Vav2 (uniprotkb:P52735) by array technology (MI:0008)MINT-7908458: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to mSck/ShcB (uniprotkb:Q8BMC3) by array technology (MI:0008)MINT-7908091: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Yes (uniprotkb:P07947) by array technology (MI:0008)MINT-7908219: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Src (uniprotkb:P00523) by array technology (MI:0008)MINT-7908123: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Fer (uniprotkb:P16591) by array technology (MI:0008)MINT-7908410: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to CrkL (uniprotkb:P46109) by array technology (MI:0008)MINT-7908314, MINT-7908442: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Arg (uniprotkb:P42684) by array technology (MI:0008)MINT-7908299: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to PLCG1 (uniprotkb:P10686) by array technology (MI:0008)MINT-7908171: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Fes (uniprotkb:P07332) by array technology (MI:0008)MINT-7908027: Abi1 (uniprotkb:Q8IZP0) binds (MI:0407) to Lck (uniprotkb:P06239) by array technology (MI:0008)     

HO1 and PcyA proteins involved in phycobilin biosynthesis form a 1:2 complex with ferredoxin-1 required for photosynthesis

The HO1 and PcyA genes, encoding heme oxygenase-1 (HO1) and phycocyanobilin (PCB):ferredoxin (Fd) oxidoreductase (PcyA), respectively, are required for chromophore synthesis in photosynthetic light-harvesting complexes, photoreceptors, and circadian clocks. In the PCB biosynthetic pathway, heme first undergoes cleavage to form biliverdin. I confirmed that Fd1 induced the formation of a stable and functional HO1 complex by the gel mobility shift assay. Furthermore, analysis by a chemical cross-linking technique designed to detect protein-protein interactions revealed that HO1 and PcyA directly interact with Fd in a 1:2 ratio. Thus, Fd1, a one-electron carrier protein in photosynthesis, drives the phycobilin biosynthetic pathway.

Structured summary

MINT-7014657: Fd1 (uniprotkb:P0A3C9) and HO1 (uniprotkb:Q8DLW1) bind (MI:0407) by comigration in non-denaturing gel electrophoresis (MI:0404)MINT-7014666: HO1 (uniprotkb:Q8DLW1 and Fd1 (uniprotkb:P0A3C9) bind (MI:0407) by cross-linking studies (MI:0030)MINT-7014675: PcyA (uniprotkb:P59288) and Fd1 (uniprotkb:P0A3C9) bind (MI:0407) by cross-linking studies (MI:0030)     

Phosphorylation of more than one site is required for tight interaction of human tau protein with 14-3-3ζ

Serine residues phosphorylated by protein kinase A (PKA) in the shortest isoform of human tau protein (τ3) were sequentially replaced by alanine and interaction of phosphorylated τ3 and its mutants with 14-3-3 was investigated. Mutation S156A slightly decreased interaction of phosphorylated τ3 with 14-3-3. Double mutations S156A/S267A and especially S156A/S235A, strongly inhibited interaction of phosphorylated τ3 with 14-3-3. Thus, two sites located in the Pro-rich region and in the pseudo repeats of τ3 are involved in phosphorylation-dependent interaction of τ3 with 14-3-3. The state of τ3 phosphorylation affects the mode of 14-3-3 binding and by this means might modify tau filament formation.

Structured summary

MINT-7233358, MINT-7233372, MINT-7233384: 14-3-3 zeta (uniprotkb:P63104) and Tau 3 (uniprotkb:P10636-3) bind (MI:0407) by molecular sieving (MI:0071)MINT-7233323, MINT-7233334, MINT-7233346: Tau 3 (uniprotkb:P10636-3) and 14-3-3 zeta (uniprotkb:P63104) bind (MI:0407) by crosslinking studies (MI:0030)MINT-7233285, MINT-7233297, MINT-7233310: 14-3-3 zeta (uniprotkb:P63104) and Tau 3 (uniprotkb:P10636-3) bind (MI:0407) by comigration in non-denaturing gel electrophoresis (MI:0404)     

The interaction between EAP30 and ELL is modulated by MCM2

ELL-associated protein 30 (EAP30) was initially characterized as a component of the Holo-ELL complex, which contains the elongation factor ELL. Both ELL and Holo-ELL stimulate RNA pol II elongation in vitro. However, ELL and not Holo-ELL inhibits RNA pol II initiation. It is not clear how these two discrete functions of ELL are regulated. Here we report that mini-chromosome maintenance 2 (MCM2) binds to EAP30 and show that MCM2 competes with ELL for binding to EAP30 thus potentially modulating the stability of Holo-ELL.

Structured summary

MINT-7277033: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with RPB1 (uniprotkb:P24928) by anti tag coimmunoprecipitation (MI:0007)MINT-7277085: EAP30 (uniprotkb:Q96H20) binds (MI:0407) to ELL (uniprotkb:P55199) by pull down (MI:0096)MINT-7277072: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with ELL (uniprotkb:P55199) by anti tag coimmunoprecipitation (MI:0007)MINT-7277100: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with ELL (uniprotkb:P55199) by competition binding (MI:0405)MINT-7277153: MCM2 (uniprotkb:P49736) binds (MI:0407) to ELL (uniprotkb:P55199) by pull down (MI:0096)MINT-7276989: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with MCM2 (uniprotkb:P49736) by pull down (MI:0096)MINT-7277005: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with RPB1 (uniprotkb:P24928) by pull down (MI:0096)MINT-7276960, MINT-7277168: MCM2 (uniprotkb:P49736) physically interacts (MI:0915) with EAP30 (uniprotkb:Q96H20) by two hybrid (MI:0018)MINT-7276971, MINT-7277121, MINT-7277137: MCM2 (uniprotkb:P49736) binds (MI:0407) to EAP30 (uniprotkb:Q96H20) by pull down (MI:0096)MINT-7277018, MINT-7277061: EAP30 (uniprotkb:Q96H20) physically interacts (MI:0915) with MCM2 (uniprotkb:P49736) by anti tag coimmunoprecipitation (MI:0007)     

Direct proteasome binding and subsequent degradation of unspliced XBP-1 prevent its intracellular aggregation

The non-canonical splicing of XBP-1 mRNA is a hallmark of the mammalian unfolded protein response (UPR). The proteasomal degradation of unspliced XBP-1 (XBP-1u) facilitates the termination of the UPR. Thus, understanding the mechanism of XBP-1u degradation may allow control over UPR duration and intensity.We show that XBP-1u interacts with purified 20S proteasomes through its unstructured C-terminus, which leads to its degradation in a manner that autonomously opens the proteasome gate. In living cells, the C-terminus of XBP-1u accumulates in aggresome structures in the presence of proteasome inhibitors. We propose that direct proteasomal degradation of XBP-1u prevents its intracellular aggregation.

Structured summary

MINT-7302217: XBP1-u (uniprotkb:P17861-1) binds (MI:0407) to Proteasome subunit alpha 7.2 (uniprotkb:O14818) by pull down (MI:0096)MINT-7302148: Vimentin (uniprotkb:P08670) and XBP1-u (uniprotkb:P17861-1) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7302163: XBP1-u (uniprotkb:P17861-1) binds (MI:0407) to Proteasome subunit alpha 5 (uniprotkb:P28066) by pull down (MI:0096)MINT-7302186: XBP1-u (uniprotkb:P17861-1) binds (MI:0407) to Proteasome subunit alpha 6 (uniprotkb:P60900) by pull down (MI:0096)     

Reassessment of the role of FKBP38 in the Rheb/mTORC1 pathway

The small G-protein Rheb regulates cell growth via the mTORC1 complex by incompletely understood mechanisms. Recent studies document that Rheb activates mTORC1 via direct, GTP-dependent interaction with the peptidyl-prolyl-cis/trans-isomerase FKBP38, which is proposed to act as an inhibitor of mTORC1. We have conducted a comprehensive biochemical characterization of the Rheb/FKBP38 interaction. Using three different in vitro assays we did not detect an interaction between Rheb and FKBP38. Cell biological experiments illustrate that FKBP38 plays only a very minor, if any, role in mTORC1 activation. Our data document that FKBP38 is not the long-sought Rheb effector linking Rheb to mTORC1 activation.

Structured summary

MINT-6946532: Ral (uniprotkb:P11233) binds (MI:0407) to Ha-Ras (uniprotkb:P01112) by pull down (MI:0096)MINT-6946500: RAF (uniprotkb:P04049) binds (MI:0407) to RHEB2 (uniprotkb:Q15382) by pull down (MI:0096)MINT-6946517: RAF (uniprotkb:P04049) binds (MI:0407) to Ha-Ras (uniprotkb:P01112) by pull down (MI:0096)     

POSH2 is a RING finger E3 ligase with Rac1 binding activity through a partial CRIB domain

The Plenty of SH3 domains protein (POSH) is an E3 ligase and a scaffold in the JNK mediated apoptosis, linking Rac1 to downstream components.We here describe POSH2 which was identified from a p21-activated kinase 2 (PAK2) interactor screen. POSH2 is highly homologous with other members of the POSH family; it contains four Src homology 3 (SH3) domains and a RING finger domain which confers E3 ligase activity to the protein. In addition POSH2 contains an N-terminal extension which is conserved among its mammalian counterparts. POSH2 interacts with GTP-loaded Rac1. We have mapped this interaction to a previously unrecognized partial Cdc42/Rac1-interactive binding domain.

Structured summary

MINT-7987761: POSH1 (uniprotkb:Q9HAM2) physically interacts (MI:0915) with Ubiquitin (uniprotkb:P62988) by anti tag coimmunoprecipitation (MI:0007)MINT-7987932: PAK2 (uniprotkb:Q13177) binds (MI:0407) to CDC42 (uniprotkb:Q07912) by solid phase assay (MI:0892)MINT-7987908: POSH1 (uniprotkb:Q9HAM2) binds (MI:0407) to Rac1 (uniprotkb:P63000) by solid phase assay (MI:0892)MINT-7987880: POSH2 (uniprotkb:Q8TEJ3) binds (MI:0407) to Rac1 (uniprotkb:P63000) by solid phase assay (MI:0892)MINT-7987734: POSH2 (uniprotkb:Q8TEJ3) physically interacts (MI:0915) with Ubiquitin (uniprotkb:P62988) by anti tag coimmunoprecipitation (MI:0007)MINT-7987779, MINT-7987804, MINT-7987824, MINT-7987838, MINT-7987853: Rac1 (uniprotkb:P63000) physically interacts (MI:0915) with POSH2 (uniprotkb:Q8TEJ3) by anti tag coimmunoprecipitation (MI:0007)MINT-7987920: PAK2 (uniprotkb:Q13177) binds (MI:0407) to Rac1 (uniprotkb:P63000) by solid phase assay (MI:0892)     

Stoichiometric protein complex formation and over-expression using the prokaryotic native operon structure

In prokaryotes, operon encoded proteins often form protein-protein complexes. Here, we show that the native structure of operons can be used to efficiently overexpress protein complexes. This study focuses on operons from mycobacteria and the use of Mycobacterium smegmatis as an expression host. We demonstrate robust and correct stoichiometric expression of dimers to higher oligomers. The expression efficacy was found to be largely independent of the intergenic distances. The strategy was successfully extended to express mycobacterial protein complexes in Escherichia coli, showing that the operon structure of gram-positive bacteria is also functional in gram-negative bacteria. The presented strategy could become a general tool for the expression of large quantities of pure prokaryotic protein complexes for biochemical and structural studies.

Structured summary

MINT-7542207: ESAT-6 (uniprotkb:Q50206) and CFP-10 (uniprotkb:O33084) bind (MI:0407) by blue native page (MI:0276)MINT-7542534: ESAT-6 (uniprotkb:P0A564) and CFP-10 (uniprotkb:P0A566) bind (MI:0407) by X-ray crystallography (MI:0114)MINT-7542187: CFP-10 (uniprotkb:P0A566) and ESAT-6 (uniprotkb:P0A564) bind (MI:0407) by blue native page (MI:0276)MINT-7542652: CFP-10 (uniprotkb:P0A566) and ESAT-6 (uniprotkb:P0A564) bind (MI:0407) by molecular sieving (MI:0071)MINT-7542474, MINT-7542303: CFP-10 (uniprotkb:P0A566) physically interacts (MI:0915) with ESAT-6 (uniprotkb:P0A564) by pull down (MI:0096)     

Reconstitution of the mitochondrial Hsp70 (mortalin)-p53 interaction using purified proteins - Identification of additional interacting regions

Previous studies have shown that the mammalian mitochondrial 70 kDa heat-shock protein (mortalin) can also be detected in the cytosol. Cytosolic mortalin binds p53 and by doing so, prevents translocation of the tumor suppressor into the nucleus. In this study, we developed a novel binding assay, using purified proteins, for tracking the interaction between p53 and mortalin. Our results reveal that: (i) P53 binds to the peptide-binding site of mortalin which enhances the ability of the former to bind DNA. (ii) An additional previously unknown binding site for mortalin exists within the C-terminal domain of p53.

Structured summary

MINT-7557591: p53 (uniprotkb:P04637) binds (MI:0407) to DnaK (uniprotkb:P0A6Y8) by affinity chromatography technology (MI:0004)MINT-7557644: mortalin (uniprotkb:P38646) binds (MI:0407) to p53 (uniprotkb:P04637) by pull down (MI:0096)MINT-7557580, MINT-7557611: p53 (uniprotkb:P04637) binds (MI:0407) to mortalin (uniprotkb:P38646) by affinity chromatography technology (MI:0004)     

Regulation of nuclear localization signal-importin α interaction by Ca2+/S100A6

Although the precise intracellular roles of S100 proteins are not fully understood, these proteins are thought to be involved in Ca²⁺-dependent diverse signal transduction pathways. In this report, we identified importin α as a novel target of S100A6. Importin α contains armadillo repeats, essential for binding to nuclear localization signals. Based on the results from GST pull-down assay, gel-shift assay, and co-immunoprecipitation, we demonstrated that S100A6 specifically interacts with the armadillo repeats of importin α in a Ca²⁺-dependent manner, resulting in inhibition of the nuclear localization signal (NLS)-importin α complex formation in vitro and in vivo. These results indicate S100A6 may regulate the nuclear transport of NLS-cargos in response to increasing concentrations of intracellular Ca²⁺.

Structured summary

MINT-8045244: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-8044928: Importin alpha (uniprotkb:P52292) binds (MI:0407) to S100A6 (uniprotkb:P06703) by pull down (MI:0096)MINT-8044941: Importin alpha (uniprotkb:P52292) and S100A6 (uniprotkb:P06703) bind (MI:0407) by electrophoretic mobility supershift assay (MI:0412)MINT-8044997: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by anti bait coimmunoprecipitation (MI:0006)MINT-8045031: Importin beta (uniprotkb:Q14974) physically interacts (MI:0915) with importin alpha (uniprotkb:P52293) and S100A6 (uniprotkb:P06703) by pull down (MI:0096)MINT-8044917: Importin alpha (uniprotkb:P52292) binds (MI:0407) to S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-8045257: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by pull down (MI:0096)MINT-8045015: Importin beta (uniprotkb:Q14974) physically interacts (MI:0915) with importin alpha (uniprotkb:P52293) and S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-8045267: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) and npm2 (uniprotkb:Q6GQG6) by pull down (MI:0096)MINT-8045316: Importin beta (uniprotkb:Q14974) physically interacts (MI:0915) with importin alpha (uniprotkb:P52293) by pull down (MI:0096)MINT-8045302: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with NPM1 (uniprotkb:P06748) and S100A2 (uniprotkb:P29034) by pull down (MI:0096)MINT-8045290: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with npm2 (uniprotkb:Q6GQG6) by pull down (MI:0096)MINT-8044963, MINT-8044985: Importin alpha (uniprotkb:P52292) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by anti bait coimmunoprecipitation (MI:0006)MINT-8044951: Importin alpha (uniprotkb:P52292) and S100A2 (uniprotkb:P29034) bind (MI:0407) by electrophoretic mobility supershift assay (MI:0412)     

IbpA the small heat shock protein from Escherichia coli forms fibrils in the absence of its cochaperone IbpB

Small heat shock proteins (sHsps) associate with aggregated proteins, changing their physical properties in such a way that chaperone mediated disaggregation becomes much more efficient. In Escherichia coli two small Hsps, IbpA and IbpB, exist. They are 48% identical at the amino acid level, yet their roles in stabilisation of protein aggregates are quite distinct. Here we analysed the biochemical properties of IbpA. We found that IbpA assembles into protofilaments which in turn form mature fibrils. Such fibrils are atypical for sHsps. Interaction of IbpA with either its cochaperone IbpB or an aggregated substrate blocks IbpA fibril formation.

Structured summary

MINT-7876715: ibpA (uniprotkb:P0C054) and ibpA (uniprotkb:P0C054) bind (MI:0407) by molecular sieving (MI:0071)MINT-7888427: ibpB (uniprotkb:P0C058) and ibpB (uniprotkb:P0C058) bind (MI:0407) by molecular sieving (MI:0071)MINT-7888448: ibpA (uniprotkb:P0C054) and ibpA (uniprotkb:P0C054) bind (MI:0407) by electron microscopy (MI:0040)MINT-7888434: ibpB (uniprotkb:P0C058) and ibpB (uniprotkb:P0C058) bind (MI:0407) by electron microscopy (MI:0040)MINT-7888459: ibpA (uniprotkb:P0C054) and ibpA (uniprotkb:P0C054) bind (MI:0407) by fluorescence microscopy (MI:0416)     

A novel association of mGluR1a with the PDZ scaffold protein CAL modulates receptor activity

Metabotropic glutamate receptor subtype 1a (mGluR1a) associates with the proteins mediating its receptor activity, suggesting a complex-controlled function of mGluR1a. Here, using glutathione-S-transferase pull-down, co-immnoprecipitation and immnoflurescence assays in vitro and in vivo, we have found CFTR-associated ligand (CAL) to be a novel binding partner of mGluR1a, through its PSD95/discslarge/ZO1homology domain. Deletion of mGluR1a-carboxyl terminus (CT) or mutation of Leu to Ala in the CT of mGluR1a reduces the association, indicating the essential binding region of mGluR1a for CAL. Functionally, the interaction of mGluR1a with CAL was shown to inhibit mGluR1a-mediated ERK1/2 activation, without an apparent effect, via the C-terminal-truncated receptor. These findings might provide a novel mechanism for the regulation of mGluR1a-mediated signaling through the interaction with CAL.

Structured summary

MINT-6797987, MINT-6798009:

NHERF-2 (uniprotkb:Q15599) binds (MI:0407) to mGluR1a (uniprotkb:Q9R0W0) by proteinarray (MI:0089)

MINT-6798026, MINT-6798048, MINT-6798066:

mGluR1a (uniprotkb:Q9R0W0) physically interacts (MI:0218) with CAL (uniprotkb:Q9HD26) by pull down (MI:0096)

MINT-6797953, MINT-6797970:

NHERF-1 (uniprotkb:O14745) binds (MI:0407) to mGluR1a (uniprotkb:Q9R0W0) by protein array (MI:0089)

MINT-6797935:

CAL (uniprotkb:Q9HD26) binds (MI:0407) to mGluR1a (uniprotkb:Q9R0W0) by protein array (MI:0089)

MINT-6798084:

CAL (uniprotkb:Q9HD26) binds (MI:0407) to mGluR1a (uniprotkb:Q9R0W0) by filter binding (MI:0049)

MINT-6798134:

mGluR1a (uniprotkb:Q9R0W0) physically interacts (MI:0218) with CAL (uniprotkb:Q9HD26) by anti tag coimmunoprecipitation (MI:0007)

MINT-6798158:

CAL (uniprotkb:B4F775) physically interacts (MI:0218) with mGluR1a (uniprotkb:Q9R0W0) by anti bait coimmunoprecipitation (MI:0006)

MINT-6798233:

CAL (uniprotkb:Q9HD26) colocalizes (MI:0403) with mGluR1a (uniprotkb:Q9R0W0) by fluorescence microscopy (MI:0416)

     

Molecular determinants of the interactions between SRC-1 and LXR/RXR heterodimers

Liver X receptor (LXR)/retinoid X receptor (RXR) heterodimers have been shown to perform critical functions in cholesterol and lipid metabolism. Here, we have conducted a comparative analysis of the contributions of LXR and RXR binding to steroid receptor coactivator-1 (SRC-1), which contains three copies of the NR box. We demonstrated that the coactivator-binding surface of LXR, but not that of RXR, is critically important for physical and functional interactions with SRC-1, thereby confirming that RXR functions as an allosteric activator of SRC-1-LXR interaction. Notably, we identified NR box-2 and -3 as the essential binding targets for the SRC-1-induced stimulation of LXR transactivity, and observed the competitive in vitro binding of NR box-2 and -3 to LXR.

Structured summary

MINT-7986678, MINT-7986639, MINT-7986700, MINT-7986720, MINT-7986736, MINT-7986760, MINT-7986787: LXR (uniprotkb:Q13133) physically interacts (MI:0915) with SRC1 (uniprotkb:Q15788) and RXR (uniprotkb:P19793) by pull down (MI:0096)MINT-7986596, MINT-7986621: SRC1 (uniprotkb:Q15788) physically interacts (MI:0915) with LXR (uniprotkb:Q13133) by pull down (MI:0096)MINT-7986555, MINT-7986575: LXR (uniprotkb:Q13133) physically interacts (MI:0915) with SRC1 (uniprotkb:Q15788) by two hybrid (MI:0018)MINT-7986808, MINT-7986907, MINT-7986890: SRC1 (uniprotkb:Q15788) binds (MI:0407) to LXR (uniprotkb:Q13133) by pull down (MI:0096)MINT-7986822, MINT-7986848, MINT-7986865: SRC1 (uniprotkb:Q15788) binds (MI:0407) to RXR (uniprotkb:P19793) by pull down (MI:0096)