COPII-coated vesicles mediate anterograde transport from the ER to the Golgi apparatus. COPII is composed of three parts: two coat protein complexes (Sec23/24 complex and Sec13/31 complex) and one small GTP-binding protein, Sar1 . Sec24 subunit of the coat complex has been implicated in cargo recognition . In mammal cells there are four Sec24 isoforms, termed Sec24A, Sec24B, Sec24C, and Sec24D.