P51151

Rab proteins are a family of Ras-like GTPases involved in intracellular compartment protein transport. Different members of the 40+ member rab family are responsible for docking and fusion of transport vesicles between different compartments within the cell. Rab 9 is required for trafficking mannose 6-phosphate receptor between the late endosome to trans-Golgi network (TGN). By facilitating receptor transport, rab 9 enables cells to efficiently recycle important cellular trafficking components. It is functionally necessary for rab 9, like other rab family members, to be prenylated by two 20-carbon geranylgeranyl groups at the C-terminus. Most prenylated rab 9 is membrane bound, however, 10-20% of the cellular pool of rab 9 is bound to GDP dissociation inhibitor-alpha (GDI-alpha) in the cytosol. GDI recycles prenylated, GDP bound rab 9 from their fusion targets back to their membranes of origin.