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Stromal membrane-associated proteins; a subfamily of the ArfGAP family The SMAP subfamily of Arf GTPase-activating proteins consists of the two structurally-related members, SMAP1 and SMAP2. Each SMAP member exhibits common and distinct functions in vesicle trafficking. They both bind to clathrin heavy chain molecules and are involved in the trafficking of clathrin-coated vesicles. SMAP1 preferentially exhibits GAP toward Arf6, while SMAP2 prefers Arf1 as a substrate. SMAP1 is involved in Arf6-dependent vesicle trafficking, but not Arf6-mediated actin cytoskeleton reorganization, and regulates clathrin-dependent endocytosis of the transferrin receptors and E-cadherin. SMAP2 regulates Arf1-dependent retrograde transport of TGN38/46 from the early endosome to the trans-Golgi network (TGN). SMAP2 has the Clathrin Assembly Lymphoid Myeloid (CALM)-binding domain, but SMAP1 does not.
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