9.B.135 The Membrane Trafficking Yip (Yip) Family
The YIP1 family of proteins are small membrane proteins with 5 putative TMSs with roles in membrane trafficking from the ER to the golgi. In yeast they participate in vesicle biogenesis and mediate the association of Rab proteins with membranes. Yeast YIP1 is an essential gene and can be fully complemented by a human counterpart, suggesting that the essential function of Yip1p is evolutionarily conserved (Chen and Collins, 2005). Prokaryotic homologues are found in family 9.B.29 and possibly family 3.A.1.122.
Human YIPF3 and YIPF4 are localized to the cis-Golgi. YIPF3 is synthesized in the ER as a N-glycosylated form (40 kDa), is then O-glycosylated in the Golgi and finally is cleaved at its C-terminal luminal domain. YIPF3 and YIPF4 form a complex in the Golgi apparatus. The knockdown of YIPF3 or YIPF4 in HeLa cells induced fragmentation of the Golgi apparatus (Tanimoto et al., 2011). Mutation of Yip1 domain family, member 6 (Yipf6), induces spontaneous intestinal inflammation in mice (Brandl et al., 2012).