Interactions with LC3 and polyubiquitin chains link nbr1 to autophagic protein turnover

Nbr1, a ubiquitous kinase scaffold protein, contains a PB1, and a ubiquitin-associated (UBA) domain. We show here that the nbr1 UBA domain binds to lysine-48 and -63 linked polyubiquitin-B chains. Nbr1 also binds to the autophagic effector protein LC3-A via a novel binding site. Ubiquitin-binding, but not PB1-mediated p62/SQSTM1 interaction, is required to target nbr1 to LC3 and polyubiquitin-positive bodies. Nbr1 binds additionally to proteins implicated in ubiquitin-mediated protein turnover and vesicle trafficking: ubiquitin-specific peptidases USP8, and the endosomal transport regulator p14/Robld3. Nbr1 thus contributes to specific steps in protein turnover regulation disrupted in several hereditary human diseases.

Structured summary

MINT-7034452: USP8 (uniprotkb:P40818) physically interacts (MI:0218) with NBR1 (uniprotkb:Q14596) by pull down (MI:0096)MINT-7034438: SQSTM1 (uniprotkb:Q13501) and LC3 (uniprotkb:Q9H492) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7034309: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with Ubiquitin (uniprotkb:P62988) by pull down (MI:0096)MINT-7034323: NBR1 (uniprotkb:P97432) physically interacts (MI:0218) with Ubiquitin (uniprotkb:P62988) by pull down (MI:0096)MINT-7034233: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with USP8 (uniprotkb:P40818) by two hybrid (MI:0018)MINT-7034207: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with Robld3 (uniprotkb:Q9JHS3) by two hybrid (MI:0018)MINT-7034400, MINT-7034418: NBR1 (uniprotkb:Q14596) and LC3 (uniprotkb:Q9H492) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7034167: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with Ubiquitin B (uniprotkb:Q78XY9) by two hybrid (MI:0018)MINT-7034470: NBR1 (uniprotkb:Q14596) and USP8 (uniprotkb:P40818) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7034194: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with LC3-A (uniprotkb:Q91VR7) by two hybrid (MI:0018)MINT-7034336: SQSTM1 (uniprotkb:Q13501) physically interacts (MI:0218) with Ubiquitin (uniprotkb:P62988) by pull down (MI:0096)MINT-7034375: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with LC3 (uniprotkb:Q9H492) by pull down (MI:0096)MINT-7034350: NBR1 (uniprotkb:Q14596) and Ubiquitin (uniprotkb:P62988) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7034181: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with Tmed10 (uniprotkb:Q9D1D4) by two hybrid (MI:0018)MINT-7034220: NBR1 (uniprotkb:Q14596) physically interacts (MI:0218) with ube2o (uniprotkb:Q6ZPJ3) by two hybrid (MI:0018)     

GENETIC AND MORPHOLOGICAL ANALYSES OF THE SOUTHERN BULL KELP DURVILLAEA ANTARCTICA (PHAEOPHYCEAE: DURVILLAEALES) IN NEW ZEALAND REVEAL CRYPTIC SPECIES1

Many macroalgae exhibit considerable intraspecific morphological variation, but whether such variation reflects phenotypic plasticity or underlying genetic differences is often poorly understood. We quantified both morphological and genetic variation of 96 plants from seven field sites across eastern South Island, New Zealand, to assess genetic differences between morphotypes of the southern bull kelp Durvillaea antarctica (Cham.) Har. Consistent DNA sequence differentiation across mitochondrial, plastid, and nuclear loci was correlated with two broadly sympatric morphotypes: “cape” and “thonged.” These ecologically, morphologically, and genetically distinct bull‐kelp lineages were previously considered to be environmentally determined phenotypes with no underlying genetic basis. Interestingly, the sheltered “cape” lineage appears essentially genetically uniform across its South Island range, whereas the exposed “thonged” lineage exhibits marked phylogeographic structure across its range. Results suggest that D. antarctica in New Zealand comprises two reproductively isolated species.     

Insulin receptor substrate 1 and 2 (IRS1 and IRS2): what a tangled web we weave

The insulin receptor is a transmembrane tyrosine kinase that is essential for mediating multiple intracellular signalling cascades that lead ultimately to the biological actions of insulin Tyrosine phosphorylation o f the cytosolic proteins insulin receptor substrate 1 and 2 (IRS1 and IRS2) produces protein 'scaffolding' for the assembly of effector proteins containing Src homology 2 (SH2) domains, thereby generating multisubunit signalling complexes. Although IRS1 was originally isolated as a specific insulin receptor substrate, both IRS1 and IRS2 appear to play a broader role, functioning also as proximal substrates in growth hormone and cytokine receptor signalling. Current data establish IRS1 and IRS2 as critical effectors integrating various cell-type-specific signals into distinct, but overlapping, biological responses.     

Mannitol is required for asexual sporulation in the wheat pathogen Stagonospora nodorum (glume blotch)

The physiological role of the mannitol cycle in the wheat pathogen Stagonospora nodorum (glume blotch) has been investigated by reverse genetics and metabolite profiling. A putative mannitol 2-dehydrogenase gene (Mdh1) was cloned by degenerate PCR and disrupted. The resulting mutated mdh1 strains lacked all detectable NADPH-dependent mannitol dehydrogenase activity. The mdh1 strains were unaffected for mannitol production but, surprisingly, were still able to utilize mannitol as a sole carbon source, suggesting a hitherto unknown mechanism for mannitol catabolism. The mutant strains were not compromised in their ability to cause disease or sporulate. To further our understanding of mannitol metabolism, a previously developed mannitol-1-phosphate dehydrogenase (gene mpd1) disruption construct [Solomon, Tan and Oliver (2005) Mol. Plant-Microbe Interact. 18, 110-115] was introduced into the mutated mdh1 background, resulting in a strain lacking both enzyme activities. The mpd1mdh1 strains were unable to grow on mannitol and produced only trace levels of mannitol. The double-mutant strains were unable to sporulate in vitro when grown on minimal medium for extended periods. Deficiency in sporulation was correlated with the depletion of intracellular mannitol pools. Significantly sporulation could be restored with the addition of mannitol. Pathogenicity of the double mutant was not compromised, although, like the previously characterized mpd1 mutants, the strains were unable to sporulate in planta. These findings not only question the currently hypothesized pathways of mannitol metabolism, but also identify for the first time that mannitol is required for sporulation of a filamentous fungus.     

Symmetric cyanine dyes for detecting nucleic acids

A novel approach to the design of sensitive fluorescent probes for nucleic acids detection is proposed. Suitable modifications of tri- and pentamethine cyanine dyes in the polymethine chain and/or in the heterocyclic residues can result in a significant decrease in unbound dye fluorescence intensity and an increase in dye emission intensity in the presence of DNA compared to the unsubstituted dye. The sharp enhancement in the fluorescence intensity upon dye interaction with double-stranded DNA permits the application of the modified tri- and pentamethine dyes as fluorescent probes in double-stranded DNA detection in homogeneous assays.     

Effects of genotype and age on mixed-function oxidase activities in adult Drosophila melanogaster

The mixed-function oxidases that metabolize dimethylnitrosamine, aminopyrine, benzphetamine, 7-ethoxycoumarin and benzo[alpha]pyrene were measured in adults of the Canton-S, Oregon-R and Hikone-R strains of Drosophila melanogaster. The expression of these activities is both genotype and age dependent.     

Metabolism of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mouse liver preparations

Using a mouse liver microsomal preparation, it was found that the heterocyclic ring system of MPTP underwent an initial α-oxidation to give chemically reactive metabolites that may be associated with the induction of Parkinsonism by MPTP. Subsequent oxidative metabolic transformations of these intermediates were found to give a lactam metabolite and a pyridone metabolite that potentially may interact with the neurotransmitter system.     

Marine biogeographical structure in two highly dispersive gastropods: implications for trans-Tasman dispersal

Aim  Recent genetic and ecological studies of marine invertebrate species with planktotrophic larvae have inferred high rates of gene flow across wide oceanic barriers. We therefore aim to test for the genetic signature of long-distance dispersal in two widespread and abundant marine gastropod taxa.
Location  The intertidal and shallow subtidal zones of southern Australia and New Zealand (NZ), which house similar marine invertebrate assemblages despite being separated by the 2000-km-wide Tasman Sea.
Methods  We used mtDNA cytochrome oxidase I gene sequence analysis of two gastropod genera exhibiting trans-Tasman distributions, namely Austrolittorina (Littorinidae) (139 specimens; 28 localities) and Scutus (Fissurellidae) (154 specimens; 32 localities). The cool-temperate Australian ( A. unifasciata ; S. antipodes ) and NZ ( A. antipodum ; S. breviculus ) taxa within each genus are morphologically similar but of uncertain taxonomic status.
Results  The mtDNA analyses indicate major trans-Tasman genetic discontinuities for both gastropod genera, with no evidence of recent or ongoing intercontinental gene flow. Although both Scutus and Austrolittorina show significant east–west structure within southern Australia – consistent with recent studies of regional marine phylogeography – neither taxon exhibits significant differentiation within NZ.
Main conclusions  Morphologically conserved but biogeographically disjunct gastropod populations may exhibit striking phylogeographic discontinuities, even when dispersal abilities appear to be high. On the basis of these data we reject recent calls for the synonymy of NZ and Australian lineages.     

[3H]5-Hydroxytryptamine Binding Sites: Species and Tissue Variation

Abstract: The characteristics of spiperone inhibition of [³H]5-hydroxytryptamine ([³H]5-HT; [³H]serotonin) binding were examined in dorsal (DH) and ventral (VH) hippocampus, corpus striatum (CS) or caudate nucleus (CN), and frontal cortex (FC) in the rabbit, guinea pig, and cat. Some of the properties of spiperone inhibition of [³H]5-HT binding in these species were similar to the properties previously found in the rat. Spiperone was significantly more potent in DH, VH, and FC than in CS or CN. It produced shallow or biphasic inhibition curves, resulting in Hill slopes of less than 1.0. Nonlinear regression analysis of the data showed that the inhibition curves fit a two-site binding model significantly better than a one-site model in each brain region. The dissociation constants of spiperone for the high-affinity binding site ( K _H) for all the tissues and species, except cat FC and rabbit DH, were very close to those previously found in the rat (2-13 n M ). However, the dissociation constants for the low-affinity binding site ( K _L) were different from those in the rat in all species and tissues examined, except cat FC and CS. The present data are consistent with the concept of multiple 5-HT₁ binding sites and suggest the presence of at least two, and perhaps as many as three, groups of sites in the mammalian brain.     

Accounting for biodiversity in life cycle impact assessments of forestry and agricultural systems—the BioImpact metric

The International Journal of Life Cycle Assessment - Life cycle assessment (LCA) is a useful method for assessing environmental impacts at large scales. Biodiversity and ecosystem diversity are...