Annexin XI may be involved in Ca2+- or GTP-gamma S-induced insulin secretion in the pancreatic beta-cell

The aim of this study,vas to investigate possible involvement of annexin SI in the insulin secretory machinery. In fluorescence immunocytochemistry, a nnexin XI was found in the cytoplasm of pancreatic endocrine cells and a pa ncreatic beta-cell line, MIN6, in a granular pattern, MIN6 cells also posse ssed weak and diffused annexin XI immunoreactivity in the cytoplasm, Immuno electron microscopy revealed annexin SI in the insulin granules. Insulin se cretion from streptolysin-O-permeabilized MIN6 cells was inhibited by anti- annexin SI antibody, when the release was stimulated by either Ca2+ or GTP- gamma S, but not by a protein kinase C-activating phorbol ester, Inhibition of insulin release by anti-annexin SI antibody was reproduced in permeabil ized rat islets, These findings suggest that annexin SI may be involved in the regulation of insulin secretion from the pancreatic beta-cells. (C) 200 0 Federation of European Biochemical Societies. Published by Elsevier Scien ce B.V. All rights reserved.