Isolation and Characterization of a Novel cDNA Which Identifies Both Neural‐Specific and Ubiquitously Expressed G_Sα mRNAs

Abstract: Heterotrimeric G proteins consisting of α, β, and γ subunits couple sensory, hormone, and neurotransmit‐ ter receptors to intracellular and transmembrane effectors. Several splicing variants of the G_s (the G protein that stimulates adenylyl cyclase) α subunit (G_Sα) have been described. Some of these couple receptors to stimulation of adenylyl cyclase and Ca²⁺ channels, whereas others encode truncated proteins whose functions are not currently defined. We describe a 1321N1 human astrocytoma cDNA clone for a novel G_Sα isoform isolated from astrocytoma cells (G_astro) that is identical to G_Sα‐1 with the exception of a novel 5’ sequence extending into the previously described exon 1 of G_Sα, a single base change, and an alternative polyadenylation site. Analysis by northern blotting and reverse transcription/PCR confirms the presence of an mRNA corresponding to this cDNA in astrocytoma cells. Additional northern analysis indicates that G_astro recognizes two novel G_Sα mRNAs in the rat: a 2.0‐kb mRNA expressed only in neural and neuroendocrine tissues and a 1.8‐kb mRNA that is ubiquitously expressed. Functional analysis of G_astro is complicated by the apparent insertion of alphoid satellite DNA into the transcription unit. The resulting cDNA encodes a truncated protein that may be translated from the methionine in exon 2 as previously described.