PANCREATIC-ISLET CELLS EXPRESS BST-1, A CD38-LIKE SURFACE-MOLECULE HAVING ADP-RIBOSYL CYCLASE ACTIVITY

Cyclic ADP-ribose (cADPR), a well-known stimulator of Ca2+ release fro m the intracellular Ca2+ pool, has recently emerged as a potential reg ulator of insulin secretion in pancreatic beta cells. As recently desc ribed, BST-1 is a glycosyl-phosphatidylinositol (GPI)-anchored surface molecule that exhibits homology with CD38 and Aplysia ADP-ribosyl cyc lase. Like CD38, BST-1 has both ADP-ribosyl cyclase and cADPR hydrolas e activities. As a step toward elucidating the physiological role of c ADPR in insulin secretion, we examined whether BST-I is expressed in p ancreatic islet cells. Sensitive reverse transcription-polymerase chai n reaction detected almost as abundant expression of BST-1 mRNA. in pa ncreatic islets as CD38 mRNA. Immunohistochemical analyses utilizing m inor image sections revealed that BST-1 protein is expressed in a majo rity of the cells in pancreatic islets and that at least beta cells an d, to an even greater extent, alpha cells express BST-1. These observa tions suggest the involvement of multiple enzymes in the regulation of cADPR concentrations in pancreatic islet cells. (C) 1996 Academic Pre ss, Inc.