A calcium-inhibited Drosophila adenylyl cyclase

Mammals possess a family of transmembrane, C-protein-responsive adenylyl cy clase isoforms (tmACs) encoded by distinct genes differing in their pattern s of expression and modes of biochemical regulation. Our previous work conf irmed that Drosophila melanogaster also possesses a family of tmAC isoforms defining the fly as a suitable genetic model for discerning mammalian tmAC function. We now describe a Drosophila tmAC, DAC39E, which employs a novel means for regulating its expression; differential exon utilization results in a developmental switch in DAC39E protein. DAC39E protein sequence is mo st closely related to mammalian type III AC, and it is predominantly expres sed in the central nervous system (CNS) and olfactory organs, suggesting a role in processing sensory signaling inputs. DAC39E catalytic activity is i nhibited by micromolar concentrations of calcium; therefore, DAC39E is oppo sitely regulated by calcium compared to the only other tmAC shown to be exp ressed in the Drosophila CNS, Rutabaga AC. The presence of both positively and negatively regulated tmACs suggests a complex mode of cross-talk betwee n cAMP and calcium signal transduction pathways in the fly CNS. (C) 2000 El sevier Science B.V. All rights reserved.