Glucose-stimulated insulin secretion correlates with changes in mitochondrial and cytosolic Ca2+ in aequorin-expressing INS-1 cells

J Clin Invest. 1996 Dec 1;98(11):2524-38. doi: 10.1172/JCI119071.

Abstract

Nutrient-stimulated insulin secretion is dependent upon the generation of metabolic coupling factors in the mitochondria of the pancreatic B cell. To investigate the role of Ca2+ in mitochondrial function, insulin secretion from INS-1 cells stably expressing the Ca2+-sensitive photoprotein aequorin in the appropriate compartments was correlated with changes in cytosolic calcium ([Ca2+]c) and mitochondrial calcium ([Ca2+]m). Glucose and KCl, which depolarize the cell membrane, as well as the Ca2+-mobilizing agonist, carbachol (CCh), cause substantial increases in [Ca2+]m which are associated with smaller rises in [Ca2+]c. The L-type Ca2+-channel blocker, SR7037, abolished the effects of glucose and KCl while attenuating the CCh response. Glucose-induced increases in [Ca2+]m, [Ca2+]c, and insulin secretion all demonstrate a pronounced initial peak followed by a sustained plateau. All three parameters are increased synergistically when glucose and CCh are combined. Finally, [Ca2+]m, [Ca2+]c, and insulin secretion also display desensitization phenomena following repeated additions of the three stimuli. The high sensitivity of [Ca2+]m to Ca2+ influx and the desensitization-resensitization effects can be explained by a model in which the mitochondria of INS-1 cells are strategically located to sense Ca2+ influx through plasma membrane Ca2+ channels. In conclusion, the correlation of [Ca2+]m and [Ca2+]c with insulin secretion may indicate a fundamental role for Ca2+ in the adaptation of oxidative metabolism to the generation of metabolic coupling factors and the energy requirements of exocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aequorin / biosynthesis*
  • Animals
  • Calcium / metabolism*
  • Calcium Channel Blockers / pharmacology
  • Carbachol / pharmacology
  • Cell Line
  • Cell Membrane / drug effects
  • Cell Membrane / physiology
  • Cytosol / metabolism
  • Diphosphonates / pharmacology
  • Glucose / pharmacology*
  • Insulin / metabolism*
  • Insulin Secretion
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / physiology*
  • Kinetics
  • Luminescent Measurements
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Potassium Chloride / pharmacology
  • Recombinant Proteins / biosynthesis
  • Transfection

Substances

  • Calcium Channel Blockers
  • Diphosphonates
  • Insulin
  • Recombinant Proteins
  • belfosdil
  • Aequorin
  • Potassium Chloride
  • Carbachol
  • Glucose
  • Calcium

Grant support