RCP, a Rab Coupling Protein, stimulates phagocytosis.

PAVAROTTI M; LEIVA N; COLOMBO MI; DAMIANI MT

Universidad Nacional de Cuyo. Mendoza. Argentina.

Congreso; XXI Reunión Científica Anual de la Sociedad de Biología de Cuyo.; 2003

Sociedad de Biología de Cuyo

RCP is a predominantly hydrophilic protein with a putative C2-phospholipid binding domain at its amino terminus and a Rab binding domain/predicted coiled-coil domain near their carboxy terminus. RCP interacts specifically with Rab4 and Rab11, two proteins that regulate endosomal trafficking. To evaluate the participation of RCP along the phagocytic pathway, we used fluorescence confocal microscopy and biochemical approaches. In macrophages, RCP is predominantly membrane-bound and displays a punctate vesicular pattern throughout the cytoplasm. RCP is associated to early and recycling endosomes, but not to lysosomes. We found that RCP is associated as discrete patches to early phagosomal membranes and to recycling vesicles departing from phagosomes. RCP enhances particle uptake and phagosome formation. Overexpression of H13, a truncated form of RCP containing the rab binding domain, results in an abnormal endosomal compartment. H13 probably prevents the interaction of Rab4/Rab11 with endogenous RCP by sequestering them in a nonfunctional complex. Our results demonstrate that RCP is a putative Rab effector protein that regulates phagocytosis.