Enhanced cAMP protein kinase A signaling determines improved insulin secretion in a clonal insulin-producing beta-cell line (INS-1 832/13).

Published

Journal Article

In type 2 diabetes, beta-cells become glucose unresponsive, contributing to hyperglycemia. To address this problem, we recently created clonal insulin-producing cell lines from the INS-1 insulinoma line, which exhibit glucose responsiveness ranging from poor to robust. Here, mechanisms that determine secretory performance were identified by functionally comparing glucose-responsive 832/13 beta-cells with glucose-unresponsive 832/2 beta-cells. Thus, insulin secretion from 832/13 cells maximally rose 8-fold in response to glucose, whereas 832/2 cells responded only 1.5-fold. Insulin content in both lines was similar, indicating that differences in stimulus-secretion coupling account for the differential secretory performance. Forskolin or isobutylmethylxanthine markedly enhanced insulin secretion from 832/13 but not from 832/2 cells, suggesting that cAMP is essential for the enhanced secretory performance of 832/13 cells. Indeed, 8-bromoadenosine-3',5'-cyclic monophosphorothioate, rp-isomer (Rp-8-Br-cAMPS) an inhibitor of protein kinase A (PKA), inhibited insulin secretion in response to glucose with or without forskolin. Interestingly, whereas forskolin markedly increased cAMP in 832/2 cells, 832/13 cells exhibited only a marginal rise in cAMP. This suggests that 832/13 cells are more sensitive to cAMP. Indeed, the cAMP-induced exocytotic response in patch-clamped 832/13 cells was 2-fold greater than in 832/2 cells. Furthermore, immunoblotting revealed that expression of the catalytic subunit of PKA was 2-fold higher in 832/13 cells. Moreover, when the regulatory subunit of PKA was overexpressed in 832/13 cells, to reduce the level of unbound and catalytically active kinase, insulin secretion and PKA activity were blunted. Our findings show that cAMP-PKA signaling correlates with secretory performance in beta-cells.

Full Text

Duke Authors

Cited Authors

  • Yang, S; Fransson, U; Fagerhus, L; Holst, LS; Hohmeier, HE; Renström, E; Mulder, H

Published Date

  • September 2004

Published In

Volume / Issue

  • 18 / 9

Start / End Page

  • 2312 - 2320

PubMed ID

  • 15166255

Pubmed Central ID

  • 15166255

Electronic International Standard Serial Number (EISSN)

  • 1944-9917

International Standard Serial Number (ISSN)

  • 0888-8809

Digital Object Identifier (DOI)

  • 10.1210/me.2004-0148

Language

  • eng