EFA6A, an exchange factor for Arf6, regulates early steps in ciliogenesis.

Ciliogenesis is a coordinated process initiated by the recruitment and fusion of pre-ciliary vesicles at the distal appendages of the mother centriole through mechanisms that remain unclear. Here, we report that EFA6A (also known as PSD), an exchange factor for the small G protein Arf6, is involved in early stage of ciliogenesis by promoting the fusion of distal appendage vesicles forming the ciliary vesicle. EFA6A is present in the vicinity of the mother centriole before primary cilium assembly and prior to the arrival of Arl13B-containing vesicles. During ciliogenesis, EFA6A initially accumulates at the mother centriole and later colocalizes with Arl13B along the ciliary membrane. EFA6A depletion leads to the inhibition of ciliogenesis, the absence of centrosomal Rab8-positive structures and the accumulation of Arl13B-positive vesicles around the distal appendages. Our results uncover a novel fusion machinery, comprising EFA6A, Arf6 and Arl13B, that controls the coordinated fusion of ciliary vesicles docked at the distal appendages of the mother centriole.

Role of diacylglycerol in PKD recruitment to the TGN and protein transport to the plasma membrane.

Protein kinase D (PKD) is a cytosolic serine-threonine kinase that binds to the trans-Golgi network (TGN) and regulates the fission of transport carriers specifically destined to the cell surface. PKD was found to bind diacylglycerol (DAG), and this binding was necessary for its recruitment to the TGN. Reducing cellular levels of DAG inhibited PKD recruitment and blocked protein transport from the TGN to the cell surface. Thus, a DAG-dependent, PKD-mediated signaling regulates the formation of transport carriers from the TGN in mammalian cells.