Acquisition of migratory front-rear polarity: involvement of centrosomal AKAP350 and CIP4 Facundo

TONUCCI F; HIDALGO F; FERRETI AC; FAVRE C; KIERBEL A; LAROCCA MC

Puerto Natales

Workshop; Current advances in membrane trafficking: Implications for polarity and diseases; 2014

EMBO

Epithelial mesenquimal transition (EMT) enables epithelial cells to acquire a migratory phenotype, an essential process in physiological and pathological events. This transition involves the conversion of epithelial apico-basal in migratory front-rear polarity. Early events in EMT include organization of the actin cytoskeleton at the leading edge, and orientation of the centrosome (Ct) and the Golgi apparatus (GA) towards this pole of the cell. The link between these two processes remains to be elucidated. AKAP350 (AKAP450/AKAP9) is a scaffold involved in microtubule nucleation at Ct and GA. Our previous studies demonstrated that AKAP350 interacts with the cdc42 effector CIP4. This protein is a well-established regulator of the cytoskeleton, some- how involved in EMT, which, although mainly associated with membranes, was found at the centrosomes during the polarization of certain cells. The aim of this work was to assess the participation of centrosomal AKAP350 in the initial stages of EMT. We generated hepatic HepG2 cells with decreased expression of AKAP350 (AKAP350KD) by RNA interference, or delocalization of centrosomal AKAP350 (AKAP350CTD) by expression of a fusion protein harboring the AKAP350-centrosomal targeting domain. Polarized cell migration in wound healing assays was inhibited in AKAP350KD and AKAP350CTD cells. Concomitantly, at the wound edge, there was an early significant decrease in the percentage of AKAP350CTD cells with polarized Ct and GA. HepG2 cells at the wound edge increased the centrosomal localization of CIP4, whereas AKAP350 centrosomal delocalization induced a decrease in CIP4 localization at this organelle. In conclusion, our results demonstrate that centrosomal AKAP350 participates in the early stages of EMT, and suggest that the mechanism involves CIP4 interaction with AKAP350 at the centrosomes. These results support a model where CIP4 recruitment to the centrosomes by AKAP350 works as a connection between actin remodeling and Ct and GA reorientation to the leading edge of the cell