Structure and Function of Human Vps20 and Snf7 Proteins

Biochem J. 2004 Feb 1;377(Pt 3):693-700. doi: 10.1042/BJ20031347.

Abstract

Snf7p (sucrose non-fermenting) and Vps20p (vacuolar protein-sorting) are small coil-coiled proteins involved in yeast MVB (multivesicular body) structure, formation and function. In the present study, we report the identification of three human homologues of yeast Snf7p, designated hSnf7-1, hSnf7-2 and hSnf7-3, and a single human Vps20p homologue, designated hVps20, that may have similar roles in humans. Immunofluorescence studies showed that hSnf7-1 and hSnf7-3 localized in large vesicular structures that also co-localized with late endosomal/lysosomal structures induced by overexpressing an ATPase-defective Vps4-A mutant. In contrast, overexpressed hVps20 showed a typical endosomal membrane-staining pattern, and co-expression of hVps20 with Snf7-1 dispersed the large Snf7-staining vesicles. Interestingly, overexpression of both hSnf7 and hVps20 proteins induced a post-endosomal defect in cholesterol sorting. To explore possible protein-protein interactions involving hSnf7 proteins, we used information from yeast genomic studies showing that yeast Snf7p can interact with proteins involved in MVB function. Using a glutathione S-transferase-capture approach with several mammalian homologues of such yeast Snf7p-interacting proteins, we found that all three hSnf7s interacted with mouse AIP1 [ALG-2 (apoptosis-linked gene 2) interacting protein 1], a mammalian Bro1p [BCK1 (bypass of C kinase)-like resistance to osmotic shock]-containing protein involved in cellular vacuolization and apoptosis. Whereas mapping experiments showed that the N-terminus of AIP1 containing both a Bro1 and an alpha-helical domain were required for interaction with hSnf7-1, Snf7-1 did not interact with another human Bro1-containing molecule, rhophilin-2. Co-immunoprecipitation experiments confirmed the in vivo interaction of hSnf7-1 and AIP1. Additional immunofluorescence experiments showed that hSnf7-1 recruited cytosolic AIP1 to the Snf7-induced vacuolar-like structures. Together these results suggest that mammalian Vps20, AIP1 and Snf7 proteins, like their yeast counterparts, play roles in MVB function.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology*
  • Cell Line
  • Cell Line, Tumor
  • Chlorocebus aethiops
  • Cholesterol / metabolism
  • Cloning, Molecular
  • Endosomal Sorting Complexes Required for Transport
  • Endosomes / chemistry
  • HeLa Cells / chemistry
  • Humans
  • Lysosomes / chemistry
  • Membrane Proteins / chemistry*
  • Membrane Proteins / metabolism
  • Membrane Proteins / physiology*
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Protein Interaction Mapping
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology
  • Sequence Homology, Amino Acid*
  • Transport Vesicles / chemistry
  • Vesicular Transport Proteins*

Substances

  • CHMP4A protein, human
  • CHMP6 protein, human
  • Carrier Proteins
  • Endosomal Sorting Complexes Required for Transport
  • Membrane Proteins
  • Nuclear Proteins
  • SNF7 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins
  • Cholesterol

Associated data

  • GENBANK/AY329084
  • GENBANK/AY329085
  • GENBANK/AY329086
  • GENBANK/AY329087