Gap junctions and other mechanisms of cell-cell communication regulate basal insulin secretion in the pancreatic islet

R. K.P. Benninger, W. Steven Head, Min Zhang, Leslie S. Satin, David W. Piston

Research output: Contribution to journalArticlepeer-review

97 Scopus citations

Abstract

Cell-cell communication in the islet of Langerhans is important for the regulation of insulin secretion. Gap-junctions coordinate oscillations in intracellular free-calcium ([Ca 2+] i) and insulin secretion in the islet following elevated glucose. Gap-junctions can also ensure that oscillatory [Ca 2+] i ceases when glucose is at a basal levels. We determine the roles of gap-junctions and other cell-cell communication pathways in the suppression of insulin secretion under basal conditions. Metabolic, electrical and insulin secretion levels were measured from islets lacking gap-junction coupling following deletion of connexion36 (Cx36 -/-), and these results were compared to those obtained using fully isolated β-cells. K ATP loss-of-function islets provide a further experimental model to specifically study gap-junction mediated suppression of electrical activity. In isolated β-cells or Cx36 -/- islets, elevations in [Ca 2+] i persisted in a subset of cells even at basal glucose. Isolated β-cells showed elevated insulin secretion at basal glucose; however, insulin secretion from Cx36 -/- islets was minimally altered. [Ca 2+] i was further elevated under basal conditions, but insulin release still suppressed in K ATP loss-of-function islets. Forced elevation of cAMP led to PKA-mediated increases in insulin secretion from islets lacking gap-junctions, but not from islets expressing Cx36 gap junctions. We conclude there is a redundancy in how cell-cell communication in the islet suppresses insulin release. Gap junctions suppress cellular heterogeneity and spontaneous [Ca 2+] i signals, while other juxtacrine mechanisms, regulated by PKA and glucose, suppress more distal steps in exocytosis. Each mechanism is sufficiently robust to compensate for a loss of the other and still suppress basal insulin secretion.

Original languageEnglish
Pages (from-to)5453-5466
Number of pages14
JournalJournal of Physiology
Volume589
Issue number22
DOIs
StatePublished - Nov 2011

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