[Betacellulin: a new growth factor for vascular smooth muscle cells]

Betacellulin, a new member of the epidermal growth factor family, has been purified from the conditioned media of mouse pancreatic beta tumor cells. Purified betacellulin is a single chain glycoprotein with a molecular weight of approximately 32K. This factor is a potent mitogen for retinal pigment epithelial cells and vascular smooth muscle cells. Molecular cloning of the mouse and human cDNAs reveals that the mature form of this factor, composed of 80 amino acid residues, appears to be processed from a larger transmembrane precursor by proteolytic cleavage. Seventy nine % amino acid similarity is present between mouse and human precursor proteins. The carboxyl-terminal domains of both mouse and human betacellulins have a 50% sequence similarity with that of rat transforming growth factor alpha. The betacellulin gene is found to be expressed in several mouse tissues, including kidney, liver and pancreatic beta cells.