Inhibition of beta-cell sodium-calcium exchange enhances glucose-dependent elevations in cytoplasmic calcium and insulin secretion

Diabetes. 2010 Jul;59(7):1686-93. doi: 10.2337/db09-0630. Epub 2010 Apr 22.


Objective: The sodium-calcium exchanger isoform 1 (NCX1) regulates cytoplasmic calcium (Ca(2+)(c)) required for insulin secretion in beta-cells. NCX1 is alternatively spliced, resulting in the expression of splice variants in different tissues such as NCX1.3 and -1.7 in beta-cells. As pharmacological inhibitors of NCX1 splice variants are in development, the pharmacological profile of beta-cell NCX1.3 and -1.7 and the cellular effects of NCX1 inhibition were investigated.

Research design and methods: The patch-clamp technique was used to examine the pharmacological profile of the NCX1 inhibitor KB-R7943 on recombinant NCX1.3 and -1.7 activity. Ca(2+) imaging and membrane capacitance were used to assess the effects of KB-R7943 on Ca(2+)(c) and insulin secretion in mouse and human beta-cells and islets.

Results: NCX1.3 and -1.7 calcium extrusion (forward-mode) activity was approximately 16-fold more sensitive to KB-R7943 inhibition compared with cardiac NCX1.1 (IC(50s) = 2.9 and 2.4 vs. 43.0 micromol/l, respectively). In single mouse/human beta-cells, 1 micromol/l KB-R7943 increased insulin granule exocytosis but was without effect on alpha-cell glucagon granule exocytosis. KB-R7943 also augmented sulfonylurea and glucose-stimulated Ca(2+)(c) levels and insulin secretion in mouse and human islets, although KB-R7943 was without effect under nonstimulated conditions.

Conclusions: Islet NCX1 splice variants display a markedly greater sensitivity to pharmacological inhibition than the cardiac NCX1.1 splice variant. NCX1 inhibition resulted in glucose-dependent increases in Ca(2+)(c) and insulin secretion in mouse and human islets. Thus, we identify beta-cell NCX1 splice variants as targets for the development of novel glucose-sensitive insulinotropic drugs for type 2 diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Calcium / metabolism*
  • Cells, Cultured
  • Cytoplasm / metabolism
  • Electrophysiology
  • Exocytosis / drug effects
  • Glucose / metabolism*
  • Humans
  • Insulin / metabolism*
  • Insulin Secretion
  • Insulin-Secreting Cells / cytology
  • Insulin-Secreting Cells / drug effects
  • Insulin-Secreting Cells / metabolism*
  • Mice
  • Protein Isoforms / metabolism
  • RNA, Small Interfering
  • Sodium-Calcium Exchanger / antagonists & inhibitors
  • Sodium-Calcium Exchanger / metabolism*
  • Thiourea / analogs & derivatives
  • Thiourea / pharmacology


  • 2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate
  • Insulin
  • Protein Isoforms
  • RNA, Small Interfering
  • Sodium-Calcium Exchanger
  • sodium-calcium exchanger 1
  • Thiourea
  • Glucose
  • Calcium