hVps41 and VAMP7 function in direct TGN to late endosome transport of lysosomal membrane proteins

Nat Commun. 2013;4:1361. doi: 10.1038/ncomms2360.

Abstract

Targeted delivery of lysosome-associated membrane proteins is important for lysosome stability and function. Here we identify a pathway for transport of lysosome-associated membrane proteins directly from the trans-Golgi network to late endosomes, which exists in parallel to mannose 6-phosphate receptor and clathrin-dependent transport of lysosomal enzymes to early endosomes. By immunoelectron microscopy we localized endogenous LAMP-1 and -2 as well as LAMP-1-mGFP to non-coated, biosynthetic carriers at the trans-Golgi network and near late endosomes. These LAMP carriers were negative for mannose 6-phosphate receptor, adaptor-protein complex-1, secretory albumin and endocytic markers, but contained the homotypic fusion and protein sorting complex component hVps41 and the soluble N-ethylmaleimide-sensitive factor attachment protein receptors protein VAMP7. Knockdown of hVps41 or VAMP7 resulted in the accumulation of lysosome-associated membrane protein carriers, whereas knockdown of hVps39 or hVps18 did not, indicating that the effect of hVps41 is independent of CORVET/HOPS. Mannose 6-phosphate receptor carriers remained unaffected upon hVps41 or VAMP7 knockdown, implicating that hVps41 and VAMP7 are specifically involved in the fusion of trans-Golgi network-derived lysosome-associated membrane protein carriers with late endosomes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Clathrin / metabolism
  • Endosomes / metabolism*
  • Endosomes / ultrastructure
  • Gene Knockdown Techniques
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Hep G2 Cells
  • Humans
  • Lysosomal-Associated Membrane Protein 2
  • Lysosome-Associated Membrane Glycoproteins / metabolism*
  • Models, Biological
  • Protein Transport
  • R-SNARE Proteins / metabolism*
  • Rats
  • Receptor, IGF Type 2 / metabolism
  • Secretory Vesicles / metabolism
  • Secretory Vesicles / ultrastructure
  • Vesicular Transport Proteins / metabolism*
  • trans-Golgi Network / metabolism*
  • trans-Golgi Network / ultrastructure

Substances

  • Clathrin
  • LAMP1 protein, human
  • LAMP2 protein, human
  • Lysosomal-Associated Membrane Protein 2
  • Lysosome-Associated Membrane Glycoproteins
  • R-SNARE Proteins
  • Receptor, IGF Type 2
  • VAMP7 protein, human
  • VPS41 protein, human
  • Vesicular Transport Proteins
  • Green Fluorescent Proteins