Drak is a potential mechanotransduction partner of Filamin

Mechanosensing involves proteins detecting mechanical changes in the cytoskeleton or at cell adhesion sites. These interactions initiate signaling cascades that produce biochemical effects such as post-translational modifications or cytoskeletal rearrangements. Filamin is a ubiquitous mechanosensing protein that binds actin filaments and senses pulling forces within the cytoskeleton. Drosophila Filamin (Cheerio) is structurally similar to mammalian Filamin, with roles in egg chamber development, embryo cellularization, and integrity of muscle attachment sites and Z discs in Drosophila indirect flight muscles (IFMs). Here we report a potential novel mechanotransduction pathway involving Filamin and Drak, a death-associated protein kinase that functions as a myosin light chain kinase. We found that Drak biochemically binds mechanically activated Filamin. During embryo cellularization, Drak-GFP localization followed that of Filamin and myosin at the initiation of the cellularization furrow. During indirect flight muscle development at the pupal stage, Drak was expressed in the tendon cells and in the developing myotubes. Drak co-localized with Filamin in the tendon cells at the time of myotube attachment site maturation and Drak expression peaked in the myotubes at the compaction stage. Drak null mutant and a Filamin mutant with reduced Drak binding caused an epistatic effect on the adult muscle attachment site morphology. These results suggest that Filamin may have a role in the regulation of Drak function in response to mechanical forces.