Characterization of G-protein alpha subunits in the Gq class: expression in murine tissues and in stromal and hematopoietic cell lines.

Abstract

Murine G alpha 14 and G alpha 15 cDNAs encode distinct alpha subunits of heterotrimeric guanine nucleotide-binding proteins (G proteins). These alpha subunits are related to members of the Gq class and share certain sequence characteristics with G alpha q, G alpha 11, and G alpha 16, such as the absence of a pertussis toxin ADP-ribosylation site. G alpha 11 and G alpha q are ubiquitously expressed among murine tissues but G alpha 14 is predominantly expressed in spleen, lung, kidney, and testis whereas G alpha 15 is primarily restricted to hematopoietic lineages. Among hematopoietic cell lines, G alpha 11 mRNA is found in all cell lines tested, G alpha q is expressed widely but is not found in most T-cell lines, G alpha 15 is predominantly expressed in myeloid and B-cell lineages, and G alpha 14 is expressed in bone marrow adherent (stromal) cells, certain early myeloid cells, and progenitor B cells. Polyclonal antisera produced from synthetic peptides that correspond to two regions of G alpha 15 react with a protein of 42 kDa expressed in B-cell membranes and in Escherichia coli transformed with G alpha 15 cDNA. The expression patterns that were observed in mouse tissues and cell lines indicate that each of the alpha subunits in the Gq class may be involved in pertussis toxin-insensitive signal-transduction pathways that are fundamental to hematopoietic cell differentiation and function.