D-AKAP2, A NOVEL PROTEIN-KINASE-A ANCHORING PROTEIN WITH A PUTATIVE RGS DOMAIN

Subcellular localization directed by specific A kinase anchoring prote ins (AKAPs) is a mechanism for compartmentalization of cAMP-dependent protein kinase (PKA). Using a two-hybrid screen, a novel AKAP tvas iso lated, Because it interacts with both the type I and type II regulator y subunits, it was defined as a dual specific AKAP or D-AKAP1. Here we report the cloning and characterization of another novel cDNA isolate d from that screen. This new member of the D-AKAP family, D-AKAP2, als o binds both types of regulatory subunits, A message of 5 kb pairs was detected for D-AKAP2 in all embryonic stages and in all adult tissues tested, In brain, skeletal muscle, kidney, and testis, a 10-kb mRNA w as identified, In testis, several small mRNAs were observed, Therefore , D-AKAP2 represents a novel family of proteins. cDNA cloning from a m ouse testis library identified the full length D-AKAP2. It is composed of 372 amino acids which includes the R binding fragment, residues 33 3-372, at its C-terminus. Based on coprecipitation assays, the R bindi ng domain interacts with the N-terminal dimerization domain of R-I alp ha and R(II)alpha. A putative RGS domain was identified near the N-ter minal region of D-AKAP2. The presence of this domain raises the intrig uing possibility that D-AKAP2 may interact with a G alpha protein thus providing a link between the signaling machinery at the plasma membra ne and the downstream kinase.