The rod cGMP phosphodiesterase δ subunit dissociates the small GTPase Rab13 from membranes

Abstract

Small Rab GTPases are involved in the regulation of membrane trafficking. They cycle between cytosolic and membrane-bound forms. These membrane association/dissociation are tightly controlled by regulatory proteins. To search for proteins interacting with Rab13, a small GTPase associated with vesicles in fibroblasts and predominantly with tight junctions in epithelial cells, we screened a HeLa two-hybrid cDNA library and isolated a clone encoding a protein of 17.4 kDa. This protein, almost identical to the bovine rod cGMP phosphodiesterase δ subunit, was named human δ-PDE. The δ-PDE binds specifically to Rab13. It exhibits two putative C-terminal sequences necessary for the interaction with PDZ (PSD95, Dig, ZO-1) domains contained in many proteins localized to specific plasma membrane microdomains. Immunofluorescence microscopic studies revealed that the vesicular stomatitis virus (VSV)tagged δ-PDE is localized in vesicular structures accumulated near the plasma membrane in epithelial cells. Deletion of the PDZ binding motifs impair VSV-δ-PDE subcellular distribution. Purified recombinant δ-PDE had the capacity to dissociate Rab13 from cellular membranes. Our data support the proposal that δ-PDE, but not GDP dissociation inhibitor, may serve to control the dynamic of the association of Rab13 with cellular membranes.