Function of PCP effector proteins, In, Fy and Frtz, in regulating planar cell polarity. Ying Wang¹, Jie Yan¹, Paul Adler^1,2. 1) Biology, University of Virginia, CHARLOTTESVILLE, VA; 2) Cell Biology,University of Virginia, CHARLOTTESVILLE, VA.

   The frizzled/PCP pathway plays a fundamental role in Drosophila melanogaster to establish and regulate planar cell polarity. Inturned (In), Fuzzy (Fy) and Fritz (Frtz) are PCP effector proteins that accumulate on the proximal side of wing cells. They function downstream of the core protein, such as Frizzled (Fz), and Disheveled (Dsh), but upstream of Multiple-wing-hairs (Mwh). Our research focuses on how effector proteins interact with other pathway proteins, including upstream core proteins and the downstream protein Mwh, and how this network functions.
   
   Our hypothesis is that In, Fy and Frtz work as a group by binding to each other, through protein-protein binding domains, to transfer the signals from the core proteins to Mwh, which regulates the cytoskeleton to insure hair initiation is restricted to the distal most part of the cell. We found that Fy and Frtz both bind to In, but not to each other. Our data argues that In, Fy and Frtz form a protein complex and function together in the frizzled/PCP pathway. We also found that Mwh interacts with In, but not with the upstream core protein Vang and Prickle. This suggests that Mwh is recruited to the proximal side of wing cells by the In protein. We have also found that under certain circumstances the over expression of a PPE protein can alter hair polarity and the asymmetric accumulation of upstream proteins such as Starry Night (Stan). The mechanisms by which the "downstream" components influence the localization of "upstream" proteins is under investigation.