Organization of F-actin via concerted regulation of Kette by PTP61F and dAbl.

We identify Kette, a key regulator of actin polymerization, as a substrate for Drosophila protein tyrosine phosphatase PTP61F, as well as for dAbl tyrosine kinase. We further show that dAbl is a direct substrate for PTP61F. Therefore, Kette phosphotyrosine levels are regulated both directly and indirectly by PTP61F. Kette and PTP61F genetically interact in the regulation of F-actin organization in pupal eye discs, suggesting that tyrosine phosphorylation is essential for the proper regulation of Kette-mediated actin dynamics. This hypothesis was confirmed by demonstrating the loss of Kette-mediated F-actin organization and lamella formation in S2 cells in a Kette Y482F mutant in which the dAbl phosphorylation site was eliminated. Our results establish for the first time that PTP61F and dAbl ensure proper actin organization through the coordinated and reversible tyrosine phosphorylation of Kette.