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A BLOC-1-AP-3 super-complex sorts a cis-SNARE complex into endosome-derived tubular transport carriers.

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Bowman, Shanna L 
Le, Linh 
Zhu, Yueyao 
Harper, Dawn C 
Sitaram, Anand 

Abstract

Membrane transport carriers fuse with target membranes through engagement of cognate vSNAREs and tSNAREs on each membrane. How vSNAREs are sorted into transport carriers is incompletely understood. Here we show that VAMP7, the vSNARE for fusing endosome-derived tubular transport carriers with maturing melanosomes in melanocytes, is sorted into transport carriers in complex with the tSNARE component STX13. Sorting requires either recognition of VAMP7 by the AP-3δ subunit of AP-3 or of STX13 by the pallidin subunit of BLOC-1, but not both. Consequently, melanocytes expressing both AP-3δ and pallidin variants that cannot bind their respective SNARE proteins are hypopigmented and fail to sort BLOC-1-dependent cargo, STX13, or VAMP7 into transport carriers. However, SNARE binding does not influence BLOC-1 function in generating tubular transport carriers. These data reveal a novel mechanism of vSNARE sorting by recognition of redundant sorting determinants on a SNARE complex by an AP-3-BLOC-1 super-complex.

Description

Keywords

Adaptor Protein Complex 3, Adaptor Protein Complex delta Subunits, Endosomes, Humans, Melanocytes, Melanosomes, Nerve Tissue Proteins, Protein Transport, Qa-SNARE Proteins, R-SNARE Proteins

Journal Title

J Cell Biol

Conference Name

Journal ISSN

0021-9525
1540-8140

Volume Title

220

Publisher

Rockefeller University Press

Rights

All rights reserved
Sponsorship
Wellcome Trust (207455/Z/17/Z)