High impact information on VPS15

• We demonstrate that Gpa1 is present at endosomes, where it interacts directly with both Vps34 and Vps15 and stimulates increased production of phosphatidylinositol 3-phosphate [1].
• Analysis of the CHS polypeptide demonstrates that its modular architecture is similar to the yeast vacuolar sorting protein, VPS15 [2].
• The VPS15 gene encodes a novel protein kinase homolog that is essential for the efficient delivery of soluble hydrolases to the yeast vacuole [3].
• In addition, the in vivo phosphorylation of Vps15p is defective in these kinase domain mutants, suggesting that Vps15p may regulate specific protein phosphorylation reactions required for protein sorting to the yeast vacuole [3].
• This association may be mediated by myristate as Vps15p contains a consensus signal for N-terminal myristoylation [3].

Biological context of VPS15

• The VPS15 and VPS34 genes encode components of a novel signal transduction complex essential for the delivery of soluble vacuolar hydrolases [4].
• Vesicle-mediated protein transport: regulatory interactions between the Vps15 protein kinase and the Vps34 PtdIns 3-kinase essential for protein sorting to the vacuole in yeast [5].
• In contrast, catalytically inactive Vps15p mutants do not produce a dominant mutant phenotype because they are unable to associate with Vps34p in a wild-type manner [5].
• These studies of the VPS15-VPS34 complex indicate that intracellular protein trafficking decisions may be regulated by protein phosphorylation and phosphatidylinositol signalling events [6].
• A Pichia pastoris VPS15 homologue is required in selective peroxisome autophagy [7].

Anatomical context of VPS15

• VPS15 and VPS34 encode a serine/ threonine protein kinase and a phosphatidylinositol 3-kinase, respectively, that interact at the cytoplasmic face of an intracellular membrane compartment, most likely corresponding to the late Golgi [4].
• A membrane-associated complex composed of the Vps15 protein kinase and the Vps34 phosphatidylinositol 3-kinase (PtdIns 3-kinase) is essential for the delivery of proteins to the yeast vacuole [5].
• Fractionation of p2CPY accumulated in the temperature sensitive vps15 mutant revealed that the vps15 transport block did not occur in the endosome-like compartment but rather in the late Golgi complex, presumably the site of CPY sorting [8].

Associations of VPS15 with chemical compounds

• Analysis of a temperature-conditional allele of VPS15, in which a shift to the nonpermissive temperature leads to a decrease in cellular PtdIns(3)P levels, indicates that the loss of Vps15p function leads to a defect in activation of Vps34p [5].
• In methanol-grown cells of a P. pastoris VPS15 deletion strain, the levels of peroxisomal marker enzymes remained high after addition of excess glucose or ethanol [7].
• Subcellular fractionation and sucrose density gradients indicate that Vps15p is responsible for the association of Vps34p with an intracellular membrane fraction [9].
• Biochemical characterization of the autophosphorylation reaction catalyzed by Vps15p demonstrates that it is a functional serine/threonine protein kinase [10].

Regulatory relationships of VPS15

• Consistent with this, mutations altering highly conserved residues in the lipid kinase domain of Vps34p lead to a dominant-negative phenotype resulting from titration of activating Vps15 proteins [5].

Other interactions of VPS15

• Biochemical fractionation experiments have established that Ycf1p, expressed at single-copy gene levels, co-fractionates with the vacuolar membrane and that this co-fractionation is independent of vps15, vps34 or end3 gene function [11].

Analytical, diagnostic and therapeutic context of VPS15

• Chemical cross-linking and native immunoprecipitation experiments demonstrate that Vps15p and Vps34p interact as components of a hetero-oligomeric protein complex [9].
• Protein sequence analysis and cDNA cloning show that this 150 kDa protein is highly homologous to Vps15p, a 160 kDa protein serine/threonine kinase associated with yeast Vps34p [12].

References