title: hVps41 and VAMP7 function in direct TGN to late endosome transport of lysosomal membrane proteins.
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.
authors: Department of Cell Biology, University Medical Centre Utrecht, AZU Room H02.313, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands.
authors: Maaike S
authors: MS
authors: Pols
authors: Eline
authors: E
authors: van Meel
authors: Viola
authors: V
authors: Oorschot
authors: Corlinda
authors: C
authors: ten Brink
authors: Minoru
authors: M
authors: Fukuda
authors: M G
authors: MG
authors: Swetha
authors: Satyajit
authors: S
authors: Mayor
authors: Judith
authors: J
authors: Klumperman
mesh_terms: D000818:Animals; D002966:Clathrin / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D021381:Protein Transport; D050683:R-SNARE Proteins / Q000378:metabolism*; D051381:Rats; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism / Q000648:ultrastructure; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism* / Q000648:ultrastructure; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D002966:Clathrin; D049452:Green Fluorescent Proteins; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins; D050683:R-SNARE Proteins; D017527:Receptor, IGF Type 2; D033921:Vesicular Transport Proteins; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C497811:LAMP2 protein, human; C121241:VAMP7 protein, human; C549959:VPS41 protein, human