Molecular cloning of a full-length cDNA for human type 3 adenylyl cyclase and its expression in human islets

The GK (Goto-Kakizaki) rat is a lean model of type 2 diabetes in which the diabetic state was spontaneously induced. We recently demonstrated the pres ence in GK rats of two functional point mutations in the promoter region of the type 3 adenylyl cyclase (AC3) gene that resulted in overexpression of AC3 mRNA associated with increased cAMP generation. The AC3 gene promoter m utations are the first molecular changes to be described in any specific ge ne in the CK rat. Here we report cloning of a full-length cDNA encoding hum an AC3 from a human fetal brain cDNA library using a PCR-based screening me thod. This 4142-bp cDNA predicts an open reading frame encoding 1144 amino acids containing putative 12 transmembrane-spanning domains which are typic ally found in other mammalian AC isoforms. Comparison of the translated ami no acid sequence of the AC3 gene between human and rat shows 95% homology. Using RT-PCR, clear AC3 expression was detected in isolated human islets as well as a cDNA panel containing templates from eight different tissues (br ain, heart, kidney, liver, lung, pancreas, placenta, and skeletal muscle), This wide distribution of AC3 expression may involve a number of physiologi cal and pathophysiological metabolic processes. (C) 1999 Academic Press.