The aftiphilin/p200/gamma-synergin complex.

Aftiphilin is a protein that was recently identified in database searches for proteins with motifs that interact with AP-1 and clathrin, but its function is unknown. Here we demonstrate that aftiphilin has a second, atypical clathrin binding site, YQW, that colocalizes with AP-1 by immunofluorescence, and that is enriched in ...
clathrin-coated vesicles (CCVs), confirming that it is a bona fide component of the CCV machinery. By gel filtration, aftiphilin coelutes with two other AP-1 binding partners, p200a and gamma-synergin. Antibodies against any one of these three proteins immunoprecipitate the other two, and knocking down any of the three proteins by siRNA causes a reduction in the levels of the other two, indicating that they form a stable complex. Like AP-1-depleted cells, aftiphilin-depleted cells missort a CD8-furin chimera and the lysosomal enzyme cathepsin D. However, whereas AP-1-depleted cells recycle endocytosed transferrin more slowly than untreated cells, aftiphilin-depleted cells accumulate endocytosed transferrin in a peripheral compartment and recycle it more rapidly. These observations show that in general, the aftiphilin/p200/gamma-synergin complex facilitates AP-1 function, but the complex may have additional functions as well, because of the opposing effects of the two knockdowns on transferrin recycling.
Mesh Terms:
Adaptor Protein Complex 1, Amino Acid Sequence, Base Sequence, Binding Sites, Carrier Proteins, Cathepsin D, Clathrin, Clathrin-Coated Vesicles, Endocytosis, Furin, Green Fluorescent Proteins, HeLa Cells, Humans, Membrane Proteins, Molecular Sequence Data, Multiprotein Complexes, Nerve Tissue Proteins, RNA, Small Interfering, Recombinant Fusion Proteins, Sequence Homology, Amino Acid, Transcription Factor AP-1, Transferrin
Mol Biol Cell
Date: May. 01, 2005
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