| Summary: | Soluble adenylyl cyclase (sAC) is an evolutionarily conserved CO 2 /pH/bicarbonate sensor involved in diverse physiological processes in vertebrates. In response to increases in bicarbonate, sAC catalyzes the formation of cAMP from ATP, which results in PKA‐dependent phosphorylation in target proteins. We have identified the Pacific oyster ( Crassostrea gigas ) sAC ortholog from ESTs and transcriptomic databases. Using RT‐PCR, we found sAC transcripts are present in mantle, gill and hemocytes. Using Western blot, we found Vacuolar H + ‐ATPase (VHA) and carbonic anhydrase (CA) are also localized in these tissues. We propose sAC, CA and VHA are involved in sensing and counteracting elevations in CO 2 /pH/bicarbonate levels. Understanding the cellular mechanisms for CO 2 / pH/bicarbonate sensing is key in predicting biological responses to metabolic and environmental stress. For example, Ocean Acidification (OA) models project a twofold increase in dissolved CO 2 (from 380ppm to 840ppm) by 2100, and sAC, CA and VHA might mediate homeostatic responses for acid/base regulation, reproduction and calcification. Support for this research was provided by a University of California Regents Graduate Fellowship.
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