Acyl-CoA synthetase long-chain 3-mediated fatty acid oxidation is required for TGFβ1-induced epithelial-mesenchymal transition and metastasis of colorectal carcinoma

Cancer cells frequently undergo metabolic reprogramming to support tumorigenicity and malignancy, which is recognized as a hallmark of cancer. In addition to glycolysis and glutaminolysis, alterations in fatty acid (FA) metabolism have received increasing concerns in the past few years. Recently, accumulating evidence has shown that fatty acid β-oxidation (FAO) is abnormally activated in various tumors, which is associated with the machinery of proliferation, stemness, metastasis, and radiochemotherapeutic resistance of cancer cells. Acyl-CoA synthetases 3 (ACSL3) belongs to a family of enzymes responsible for converting free long-chain FAs into fatty acyl-CoA esters, which act as substrates both for lipid synthesis and FAO.Here, we demonstrate that transforming growth factor beta 1 (TGFβ1) induces the up-regulation of ACSL3 through sterol regulatory element-binding protein 1 (SREBP1) signaling to promote energy metabolic reprogramming in colorectal carcinoma (CRC) cells. ACSL3 mediates the epithelial mesenchymal transition (EMT) and metastasis of CRC cells by activation of FAO pathway to produce ATP and reduced nicotinamide adenine dinucleotide phosphate (NADPH), which sustain redox homeostasis and fuel cancer cells for invasion and distal metastasis. Thus, targeting ACSL3 and FAO metabolic pathways might be exploited for therapeutic gain for CRC and other FAs- addicted cancers.     

SLC25A38 as a novel biomarker for metastasis and clinical outcome in uveal melanoma

Risk of metastasis is increased by the presence of chromosome 3 monosomy in uveal melanoma (UM). This study aimed to identify more accurate biomarker for risk of metastasis in UM. A total of 80 patients with UM from TCGA were assigned to two groups based on the metastatic status, and bioinformatic analyses were performed to search for critical genes for risk of metastasis. SLC25A38, located on chromosome 3, was the dominant downregulated gene in metastatic UM patients. Low expression of SLC25A38 was an independent predictive and prognostic factor in UM. The predictive potential of SLC25A38 expression was superior to that of pervious reported biomarkers in both TCGA cohort and {"type":"entrez-geo","attrs":{"text":"GSE22138","term_id":"22138"}}GSE22138 cohort. Subsequently, its role in promoting metastasis was explored in vitro and in vivo. Knock-out of SLC25A38 could enhance the migration ability of UM cells, and promote distant metastasis in mice models. Through the inhibition of CBP/HIF-mediated pathway followed by the suppression of pro-angiogenic factors, SLC25A38 was situated upstream of metastasis-related pathways, especially angiogenesis. Low expression of SLC25A38 promotes angiogenesis and metastasis, and identifies increased metastatic risk and worse survival in UM patients. This finding may further improve the accuracy of prognostic prediction for UM.Subject terms: Eye cancer, Prognostic markers     

SPA: A Quantitation Strategy for MS Data in Patient-derived Xenograft Models

With the development of mass spectrometry (MS)-based proteomics technologies, patient-derived xenograft (PDX), which is generated from the primary tumor of a patient, is widely used for the proteome-wide analysis of cancer mechanism and biomarker identification of a drug. However, the proteomics data interpretation is still challenging due to complex data deconvolution from the PDX sample that is a cross-species mixture of human cancerous tissues and immunodeficient mouse tissues. In this study, by using the lab-assembled mixture of human and mouse cells with different mixing ratios as a benchmark, we developed and evaluated a new method, SPA (shared peptide allocation), for protein quantitation by considering the unique and shared peptides of both species. The results showed that SPA could provide more convenient and accurate protein quantitation in human–mouse mixed samples. Further validation on a pair of gastric PDX samples (one bearing FGFR2 amplification while the other one not) showed that our new method not only significantly improved the overall protein identification, but also detected the differential phosphorylation of FGFR2 and its downstream mediators (such as RAS and ERK) exclusively. The tool pdxSPA is freely available at https://github.com/Li-Lab-Proteomics/pdxSPA.     

BSAP／Pax—5在B淋巴细胞发育、增殖、分化中的作用

BSAP,一个B细胞特异性激活蛋白,由Pax-5转录的核蛋白。作为核转录因子,其在B细胞的发育、增殖和分化中起重要作用。同时也影响B细胞分化晚期的Ig的分泌。     

The mechanism of PAK activation. Autophosphorylation events in both regulatory and kinase domains control activity

The p21-activated kinases (PAKs), in common with many kinases, undergo multiple autophosphorylation events upon interaction with appropriate activators. The Cdc42-induced phosphorylation of PAK serves in part to dissociate the kinase from its partners PIX and Nck. Here we investigate in detail how autophosphorylation events affect the catalytic activity of PAK by altering the autophosphorylation sites in both alpha- and betaPAK. Both in vivo and in vitro analyses demonstrate that, although most phosphorylation events in the PAK N-terminal regulatory domain play no direct role in activation, a phosphorylation of alphaPAK serine 144 or betaPAK serine 139, which lie in the kinase inhibitory domain, significantly contribute to activation. By contrast, sphingosine-mediated activation is independent of this residue, indicating a different mode of activation. Thus two autophosphorylation sites direct activation while three others control association with focal complexes via PIX and Nck.     

Identification and partial purification of GTPase-activating proteins from yeast and mammalian cells that preferentially act on Ypt1/Rab1 proteins

Two GTPase-activating proteins of apparent molecular mass of 100 kDa and 30 kDa have been partially purified from porcine liver cytosol using mammalian Ypt1/Rab1 protein as substrate. Both proteins act most efficiently on Ypt1/Rab1p, but are inactive with H-Ras p21. From the budding yeast Saccharomyces cerevisiae, a cytosolic 40 kDa yptGAP was partially purified. It accelerates the intrinsic GTPase activity of wild-type Ypt1p but not of H-Ras p21 or a mutant ypt1p with an amino acid substitution of the effector domain which renders the protein functionally inactive in yeast cells.     

H-Bonding and Positive Charge at the N(5)/O(4) Locus Are Critical for Covalent Flavin Attachment in Trametes Pyranose 2-Oxidase

Flavoenzymes perform a wide range of redox reactions in nature, and a subclass of flavoenzymes carry covalently bound cofactor. The enzyme-flavin bond helps to increase the flavin's redox potential to facilitate substrate oxidation in several oxidases. The formation of the enzyme-flavin covalent bond—the flavinylation reaction—has been studied for the past 40 years. For the most advocated mechanism of autocatalytic flavinylation, the quinone methide mechanism, appropriate stabilization of developing negative charges at the flavin N(1) and N(5) loci is crucial. Whereas the structural basis for stabilization at N(1) is relatively well studied, the structural requisites for charge stabilization at N(5) remain less clear. Here, we show that flavinylation of histidine 167 of pyranose 2-oxidase from Trametes multicolor requires hydrogen bonding at the flavin N(5)/O(4) locus, which is offered by the side chain of Thr169 when the enzyme is in its closed, but not open, state. Moreover, our data show that additional stabilization at N(5) by histidine 548 is required to ensure high occupancy of the histidyl-flavin bond. The combination of structural and spectral data on pyranose 2-oxidase mutants supports the quinone methide mechanism. Our results demonstrate an elaborate structural fine-tuning of the active site to complete its own formation that couples efficient holoenzyme synthesis to conformational substates of the substrate-recognition loop and concerted movements of side chains near the flavinylation ligand.     

A posttranslationally regulated protease, VheA, is involved in the liberation of juveniles from parental spheroids in Volvox carteri

The lineage of volvocine algae includes unicellular Chlamydomonas and multicellular Volvox in addition to their colonial relatives intermediate in size and cell number. In an asexual life cycle, daughter cells of Chlamydomonas hatch from parental cell walls soon after cell division, while Volvox juveniles are released from parental spheroids after the completion of various developmental events required for the survival of multicellular juveniles. Thus, heterochronic change in the timing of hatching is considered to have played an important role in the evolution of multicellularity in volvocine algae. To study the hatching process in Volvox carteri, we purified a 125-kD Volvox hatching enzyme (VheA) from a culture medium with enzymatic activity to degrade the parental spheroids. The coding region of vheA contains a prodomain with a transmembrane segment, a subtilisin-like Ser protease domain, and a functionally unknown domain, although purified 125-kD VheA does not contain a prodomain. While 143-kD VheA with a prodomain is synthesized long before the hatching stage, 125-kD VheA is released into the culture medium during hatching due to cleavage processing at the site between the prodomain and the subtilisin-like Ser protease domain, indicating that posttranslational regulation is involved in the determination of the timing of hatching.     

TGF-β isoforms inhibit hepatitis C virus propagation in transforming growth factor beta/SMAD protein signalling pathway dependent and independent manners

Transforming growth factor beta (TGF-β) plays an important role in the viral liver disease progression via controlling viral propagation and mediating inflammation-associated responses. However, the antiviral activities and mechanisms of TGF-β isoforms, including TGF-β1, TGF-β2 and TGF-β3, remain unclear. Here, we demonstrated that all of the three TGF-β isoforms were increased in Huh7.5 cells infected by hepatitis C virus (HCV), but in turn, the elevated TGF-β isoforms could inhibit HCV propagation with different potency in infectious HCV cell culture system. TGF-β isoforms suppressed HCV propagation through interrupting several different stages in the whole HCV life cycle, including virus entry and intracellular replication, in TGF-β/SMAD signalling pathway–dependent and TGF-β/SMAD signalling pathway–independent manners. TGF-β isoforms showed additional anti-HCV activities when combined with each other. However, the elevated TGF-β1 and TGF-β2, not TGF-β3, could also induce liver fibrosis with a high expression of type I collagen alpha-1 and α-smooth muscle actin in LX-2 cells. Our results showed a new insight into TGF-β isoforms in the HCV-related liver disease progression.