Search Results
You are looking at 1 - 1 of 1 items for
- Author: Abner Louis Notkins x
- Refine by access: All content x
Search for other papers by Jean-Claude Henquin in
Google Scholar
PubMed
Search for other papers by Myriam Nenquin in
Google Scholar
PubMed
Search for other papers by Andras Szollosi in
Google Scholar
PubMed
Search for other papers by Atsutaka Kubosaki in
Google Scholar
PubMed
Search for other papers by Abner Louis Notkins in
Google Scholar
PubMed
Islet antigen-2 (IA-2 or ICA 512) and IA-2β (or phogrin) are major autoantigens in type 1 diabetes. They are located in dense core secretory vesicles including insulin granules, but their role in β-cell function is unclear. Targeted disruption of either IA-2 or IA-2β, or both, impaired glucose tolerance, an effect attributed to diminution of insulin secretion. In this study, we therefore characterized the dynamic changes in cytosolic Ca2+([Ca2+]c) and insulin secretion in islets from IA-2/IA-2β double knockout (KO) mice. High glucose (15 mM) induced biphasic insulin secretion in IA-2/IA-2β KO islets, with a similar first phase and smaller second phase compared with controls. Since the insulin content of IA-2/IA-2β KO islets was ∼45% less than that of controls, fractional insulin secretion (relative to content) was thus increased during first phase and unaffected during second phase. This peculiar response occurred in spite of a slightly smaller rise in [Ca2+]c, could not be attributed to an alteration of glucose metabolism (NADPH fluorescence) and also was observed with tolbutamide. The dual control of insulin secretion via the KATP channel-dependent triggering pathway and KATP channel-independent amplifying pathway was unaltered in IA-2/IA-2β KO islets, and so were the potentiations by acetylcholine or cAMP (forskolin). Intriguingly, amino acids, in particular the cationic arginine and lysine, induced larger fractional insulin secretion in IA-2/IA-2β KO than control islets. In conclusion, IA-2 and IA-2β are dispensable for exocytosis of insulin granules, but are probably more important for cargo loading and/or stability of dense core vesicles.
