Multiple roles of a trimeric G protein in Drosophila cell polarization.

Polarization of the cellular cytoskeleton underlies many cellular processes including axon growth cone guidance, chemotaxis and yeast mating. Planar cell polarity (PCP) is a similar phenomenon in which cells in an epithelium become uniformly polarized to generate a field of aligned structures such as the hair cells of the cochlea. In Drosophila PCP is under the hierarchical control of Frizzled (Fz)-a serpentine receptor (that also functions in the Wnt signaling pathway). Serpentine receptors are routinely transduced by trimeric G-proteins, but until recently the general consensus was that Fzs were not G-protein linked. In Drosophila a G-protein (Galpha(o)) has now been identified that functions in both the Wnt and PCP pathways. Here we review the cell polarity phenotypes of Galpha(o) mutants and discuss the evidence that it plays multifarious roles in PCP and the organization of the cytoskeleton.