An activating mutation in AGEF-1, a putative Arf GEF, causes yolk extrusion from C. elegans embryos

C. elegans AGEF-1, an ortholog of human ARFGEF1 and ARFGEF2, functions with ARF-1, ARF-5 and the AP-1 clathrin adaptor to regulate membrane trafficking. Similar phenotypes induced by the agef-1(vh4[E1028K]) allele and agef-1(RNAi) suggested that agef-1(vh4) was a hypomorph. Here we report that agef-1(vh4) results in extrusion of yolk from the embryo. This is suppressed by RNAi of agef-1, arf-1, arf-5 but not AP-1. Based on structure of the yeast AGEF-1 ortholog, Sec7p, the E1028K change is predicted to activate AGEF-1. We propose that Arf GTPase cycling is required to regulate trafficking with AP-1 but not with Arf effectors regulating yolk trafficking.