Gea1

Gea1 is a Golgi-associated guanine nucleotide exchange factor (GEF) for the small GTPase Arf1 in the budding yeast Saccharomyces cerevisiae. It is a member of the GBF1 family of ARF GEFs and is conserved with mammalian GBF1. Gea1 works with Gea2 to drive Arf1 activation at Golgi membranes, promoting recruitment of COPI coats and driving vesicle formation in the early secretory pathway.

Gea1 activates Arf1 by catalyzing exchange of GDP for GTP on Arf1. The activated Arf1-GTP associates with Golgi membranes to recruit coatomer and adaptor proteins, shaping Golgi-derived vesicles that traffic proteins between the ER and Golgi and within Golgi cisternae. Through this activity Gea1 contributes to Golgi structure maintenance, trafficking efficiency, and overall cisternal organization.

Structurally, Gea1 contains a conserved Sec7 catalytic domain responsible for its nucleotide exchange activity, as well as N- and C-terminal regions that mediate localization, membrane association, and interactions with regulatory factors. In yeast, Gea1 and Gea2 function redundantly to support essential Golgi pathways, and loss of both genes is lethal, whereas single deletions cause growth defects.

Gea1 is sensitive to brefeldin A (BFA), a fungal metabolite that inhibits several Sec7-family GEFs, linking Gea1 function to the BFA-sensitive Arf1 activation pathway. The protein is predominantly Golgi-associated in vivo and is widely studied as a model for conserved mechanisms of Arf-regulated vesicle trafficking.