MOLECULAR CHARACTERIZATION OF A NOVEL A-KINASE ANCHOR PROTEIN FROM DROSOPHILA-MELANOGASTER

Activation of protein kinase A (PKA) at discrete intracellular sites f acilitates oogenesis and development in Drosophila, Thus, PKA-anchor p rotein complexes may involved in controlling these crucial biological processes, Evaluation of this proposition requires knowledge of PKA bi nding/targeting proteins in the fly, We now report the discovery and c haracterization of cDNAs encoding a novel, Drosophila A kinase anchor protein, DAKAP550, DAKAP550 is a large (>2300 amino acids) acidic prot ein that is maximally expressed in anterior tissues, It binds regulato ry subunits (RII) of both mammalian and Drosophila PKAII isoforms. The tethering region of DAKAP550 includes two proximal, but noncontiguous RII-binding sites (B1 and B2), The B1 domain (residues 1406-1425) bin ds RII similar to 20-fold more avidly than B2 (amino acids 1350-1369). Affinity-purified anti-DAKAP550 IgGs were exploited to demonstrate th at the anchor protein is expressed in many cells in nearly all tissues throughout the lifespan of the fly, However, DAKAP550 is highly enric hed and asymmetrically positioned in subpopulations of neurons and in apical portions of cells in gut and trachea. The combination of RII (P KAII) binding activity with differential expression polarized localiza tion is consistent with a role for DAKAP550 in creating target loci fo r the reception of signals carried by cAMP. The DAKAP550 gene was mapp ed to the 4F1.2 region of the X chromosome; flies that carry a deletio n for this portion of the X chromosome lack DAKAP550 protein.