BLOC-1 complex deficiency alters the targeting of adaptor protein complex-3 cargoes.
Mutational analyses have revealed many genes that are required for proper biogenesis of lysosomes and lysosome-related organelles. The proteins encoded by these genes assemble into five distinct complexes (AP-3, BLOC-1-3, and HOPS) that either sort membrane proteins or interact with SNAREs. Several of these seemingly distinct complexes cause similar phenotypic defects when they are rendered defective by mutation, but the underlying cellular mechanism is not understood. Here, we show that the BLOC-1 complex resides on microvesicles that also contain AP-3 subunits and membrane proteins that are known AP-3 cargoes. Mouse mutants that cause BLOC-1 or AP-3 deficiencies affected the targeting of LAMP1, phosphatidylinositol-4-kinase type II alpha, and VAMP7-TI. VAMP7-TI is an R-SNARE involved in vesicle fusion with late endosomes/lysosomes, and its cellular levels were selectively decreased in cells that were either AP-3- or BLOC-1-deficient. Furthermore, BLOC-1 deficiency selectively altered the subcellular distribution of VAMP7-TI cognate SNAREs. These results indicate that the BLOC-1 and AP-3 protein complexes affect the targeting of SNARE and non-SNARE AP-3 cargoes and suggest a function of the BLOC-1 complex in membrane protein sorting.
Salazar
G
G
Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
Craige
B
B
Styers
M L
ML
Newell-Litwa
K A
KA
Doucette
M M
MM
Wainer
B H
BH
Falcon-Perez
J M
JM
Dell'Angelica
E C
EC
Peden
A A
AA
Werner
E
E
Faundez
V
V
D033963:Adaptor Protein Complex 3 / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D019599:Mossy Fibers, Hippocampal / Q000378:metabolism; D016716:PC12 Cells; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D050683:R-SNARE Proteins / Q000378:metabolism; D051381:Rats; D052118:Lysosomal-Associated Membrane Protein 1
D033963:Adaptor Protein Complex 3; D002352:Carrier Proteins; D051907:Lysosomal Membrane Proteins; D021122:Protein Subunits; D050683:R-SNARE Proteins; C052255:Lamp1 protein, mouse; D052118:Lysosomal-Associated Membrane Protein 1; C496927:Sybl1 protein, mouse