Rab11-Family of Intecting Protein 3 - FIP3 - is recruited to phagosomes via its C-teminus domain.

LEIVA N; PAVAROTTI M; COLOMBO MI; DAMIANI MT

Pinamar. Buenos Aires. Argentina

Congreso; XLI Reunión Científica Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular- SAIB; 2005

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. SAIB

FIP3 also known as arfophilin1 belongs to a novel family of Rab11-interacting proteins (FIPs), which all share a highly conserved motif at the C-terminus of the proteins, the Rab11-binding domain. It has been recently shown that FIP3-containing vesicles are recruited to the cleavage furrow and are required for a late stage of cytokinesis. To determine whether FIP3 participates in the phagocytic pathway, we investigate its intracellular localization in macrophages. By immunofluorescence, we found that the endogenous protein is predominantly membrane-bound and FIP3-positive vesicles are concentrated close to the perinuclear region of macrophages. Overexpression of FIP3 fused to the green fluorescent protein displays a similar pattern. We have also observed that Rab11-FIP3 colocalizes with Rab11 at the recycling endosomal compartment. Furthermore, FIP3 is highly enriched at the early phagosomal membranes. We show that the targeting of FIP3 to phagosomes is Rab11 dependent, since a truncated C-terminal region of FIP3 (FIP3244-756) remains membrane bound and associated to phagosomes. We have previously demonstrated that Rab11 is required for an efficient particle uptake and our present data suggest that FIP3 may act in concert with Rab11 to regulate membrane availability for particle uptake. Rab11-and FIP3-containing vesicles could be required at cellular processes where it will be necessary the delivery of large amounts of membrane such as cytokinesis and phagocytosis.