Role of Filamin A in endocytic trafficking of GPCRs

Abstract

Chemokines and their receptors (GPCR) are known to play a crucial role in directing the movement of circulating leukocytes to sites of inflammation or injury. Monocyte chemoattractant protein 1 (CCL2), and its receptor CCR2 are implicated in a wide variety of pathophysiological inflammatory processes. We have previously demonstrated that the Filamin A protein binds to the carboxyl terminal tail of the CCR2B and its binding is important for the early steps of receptor-vesicle internalization [1,2]. We have now observed using a melanoma cell line M2, devoid of filamin A, that both the ligand-activated CCR2B and Transferrin did not reach the Rab11 recycling compartment and the internalized CCR2B-vesicles remained closer to the plasma membrane in M2 cells. In order to deep into the mechanism of action of filamin A, we have investigated its role in the entry of the receptor to the different recycling compartments, Rab4-short loop and Rab11-long loop recycling. We used immunofluorescence antibody labeling, as well as, fluorescence recovery after photobleaching (FRAP) with shFLNA Hela cells to study the influence of FLNA in trafficking of CCR2B. Transferrin and CCR2B receptors recycling is affected by the lack of FLNA in shFLNA cells. In addition, we also report here that most Rab11 recovered the bleached area more rapidly in scramble control cells than in shFLNA. Rab4 recovered equally in both types of cells. Thus, our data demonstrate that FLNA has an important role in the internalization and recycling of the CCR2B and affects the localization and trafficking of Rab11-endosomes.