Sensing acid/base conditions via soluble adenylyl cyclase in aquatic animals

Abstract

Soluble adenylyl cyclase (sAC) is a recently discovered enzyme that is stimulated by bicarbonate ions to produce cAMP. In mammals, sAC is sensor of acid/base (A/B) conditions that modulates diverse physiological process, including but not limited to epithelial ion and fluid transport, sperm flagellar movement, and gene transcription. sAC also acts as an A/B sensor in shark gills, boney fish intestine, and sea urchin sperm. Here we show evidence supporting that sAC plays a similar sensing role in other aquatic organisms. (1) based on genomic and RT‐PCR results, sAC is present in Acropora reef‐building corals. In addition, coral tissue homogenates demonstrate an unusually high capacity to produce cAMP, which is stimulated by bicarbonate and sensitive to the sAC inhibitor KH7. 2) A sAC gene is present in the genome of Pacific oyster Crassostrea gigas, and sAC mRNA is expressed in gill, mantle and hemocytes. 3) sAC protein is present in several shark tissues (e.g. gill, rectal gland, eye). At least in gill and rectal gland, sAC seems to be located both in the cytoplasm and in the nucleus. 4) sAC orthologs are identifiable in EST, TSA, wgs and HTGS databases from diverse aquatic animals such as placozoan, sponge, anemone, acorn worm, sea squirt, chimera fish, skate, coelacanth, gar, catfish, trout and salmon. We propose sAC is an evolutionarily conserved A/B sensor with diverse and important physiological functions in aquatic animals. Funded by NSF grant 122041 to MT, NSF GRFP to MEB, NSF OCE PDF to MLB, and San Diego Fellowship to JNR.