An A-kinase anchoring protein is required to maintain the morphology of actin structures during oogenesis. S.M. Jackson , C.A. Berg. Dept. of Genome Sciences, University of Washington, Seattle, WA.

   Protein kinase A holoenzyme (PKA) is anchored to specific subcellular regions by interactions between regulatory subunits (Pka-R) and A-kinase anchoring proteins (AKAPs). Here, we examine the functional importance of PKA anchoring during Drosophila oogenesis by analyzing membrane integrity and actin structures in mutants with disruptions in DAKAP200, an A-kinase anchoring protein. In wild-type ovaries, Pka-RII and DAKAP200 localized to membranes and to the outer rim of ring canals. In DAKAP200 mutant ovaries, Pka-RII membrane localization decreased, leading to a destabilization of membrane structures and the formation of binucleate nurse cells. Defects in membrane integrity could be mimicked by expressing a constitutively active PKA catalytic subunit (Pka-C) throughout germline cells. Unexpectedly, nurse cells in DAKAP200 mutant ovaries also had enlarged, thin ring canals. In contrast, overexpressing DAKAP200 in the germline resulted in thicker, smaller ring canals. To investigate the role of DAKAP200 in regulating ring canal growth, we examined genetic interactions with other genes that are known to regulate ring canal morphology. DAKAP200 mutations suppressed the small ring canal phenotype produced by DSrc64B mutants, linking DAKAP200 with the non-receptor tyrosine kinase pathway. Together, these results provide evidence that PKA localization is required for morphogenesis of actin structures in an intact organism.