Cyclic ADP-ribose and Inositol 1,4,5-Trisphosphate as Alternate Second Messengers for Intracellular Ca2+ Mobilization in Normal and Diabetic β-Cells

doi:10.1074/jbc.273.5.2497

Cyclic ADP-ribose and Inositol 1,4,5-Trisphosphate as Alternate Second Messengers for Intracellular Ca²⁺ Mobilization in Normal and Diabetic β-Cells*

From the ^‡Department of Biochemistry, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-77, Miyagi, Japan, and ^¶Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, University of Tokyo, Tokyo 113, Japan

Abstract

Intracellular Ca²⁺ mobilization occurs in a variety of cellular processes and is mediated by two major systems, the inositol 1,4,5-trisphosphate (IP₃) and cyclic ADP-ribose (cADPR) systems. cADPR has been proposed to be a second messenger for insulin secretion induced by glucose in pancreatic β-cells (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993)Science 259, 370–373). Here we show that the cADPR signal system for insulin secretion is replaced by the IP₃ system in diabetic β-cells such as ob/ob mouse islets and RINm5F cells. We measured the cADPR content in these β-cells by radioimmunoassay and found that the increase of the cADPR content by glucose did not occur in ob/ob mouse islets and RINm5F cells, whereas the increased cADPR level by glucose was observed in normal rat and mouse islets. Microsomes of these diabetic β-cells released Ca²⁺ in response to IP₃ but not to cADPR. In the diabetic β-cells, CD38 (ADP-ribosyl cyclase/cADPR hydrolase) and type 2 ryanodine receptor mRNAs were scarcely detected and, in contrast, an increased expression of IP₃receptor mRNAs was observed. The diabetic β-cells secreted insulin rather by carbamylcholine than by glucose.

Footnotes

↵* This work was supported in part by grants-in-aid from the Ministry of Education, Science, Sports and Culture, Japan.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ Recipient of a fellowship from the Japan Society for the Promotion of Science.
↵‖ To whom all correspondence should be addressed: Dept. of Biochemistry, Tohoku University School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-77, Miyagi, Japan. Tel.: 81-22-717-8079; Fax: 81-22-717-8083.
↵1 The abbreviations used are: IP₃, inositol 1,4,5-trisphosphate; cADPR, cyclic ADP-ribose; KRB, Krebs-Ringer’s bicarbonate buffer; RIA, radioimmunoassay; RT, reverse transcriptase; PCR, polymerase chain reaction; BST-1, bone marrow stromal cell antigen-1; RyR, ryanodine receptor; IP₃R, IP₃ receptor; 8-NH₂-cADPR, 8-amino-cADPR.
↵2 D. E. Sabath, H. E. Broome, and M. B. Prystowsky, EBI accession no. M32599.
↵3 cADPR levels of RINm5F-CD38 clones 1 and 3 were significantly higher (42.54 ± 5.07 and 43.11 ± 4.51 fmol/μg protein, respectively) than that of RINm5F cells (0.19 ± 0.013 fmol/μg of protein, see also Table I. Insulin secretion from RINm5F-CD38 clones 1 and 3 (0.42 ± 0.11 and 0.48 ± 0.056% of total insulin in cells/h, n = 3, respectively) incubated with 20 mm glucose was also significantly higher than that of RINm5F cells (0.078 ± 0.0078% of total insulin in cells/h, n = 3).
- Received September 5, 1997.
- Revision received November 10, 1997.
The American Society for Biochemistry and Molecular Biology, Inc.