Retinal rod rhodopsin-sensitive cGMP 3',5'-cyclic phosphodiesterase subunit delta
cytosol
The rod cGMP phosphodiesterase delta subunit dissociates the small GTPase Rab13 from membranes.
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 delta subunit, was named human delta-PDE. The delta-PDE binds specifically to Rab13. It exhibits two putative C-terminal sequences necessary for the interaction with PDZ (PSD95, Dlg, ZO-1) domains contained in many proteins localized to specific plasma membrane microdomains. Immunofluorescence microscopic studies revealed that the vesicular stomatitis virus (VSV)-tagged delta-PDE is localized in vesicular structures accumulated near the plasma membrane in epithelial cells. Deletion of the PDZ binding motifs impair VSV-delta-PDE subcellular distribution. Purified recombinant delta-PDE had the capacity to dissociate Rab13 from cellular membranes. Our data support the proposal that delta-PDE, but not GDP dissociation inhibitor, may serve to control the dynamic of the association of Rab13 with cellular membranes.