Connexin 36 Controls Synchronization of Ca2+ Oscillations and Insulin Secretion in MIN6 Cells

Connexin 36 Controls Synchronization of Ca 2+ Oscillations and Insulin Secretion in MIN6 Cells Alessandra Calabrese 1 , Min Zhang 2 , Véronique Serre-Beinier 1 , David Caton 1 , Christophe Mas 1 , Leslie S. Satin 2 and Paolo Meda 1 1 Department of Morphology, University of Geneva, Geneva, Switzerland 2 Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia Abstract Cx36 is the predominant connexin isoform expressed by pancreatic β-cells. However, little is known about the role of this protein in the functioning of insulin-secreting cells. To address this question, we searched for a cell line expressing Cx36 and having glucose-induced insulin secretion comparable to that of primary β-cells. By evaluating Cx36 expression in MIN6, βTC3, RIN2A, INS1, and HIT cell lines, which differ in their sensitivity to glucose, we found that wild-type MIN6 cells fit these requirements. Therefore, we stably transfected MIN6 cells with a cDNA coding for a Cx36 antisense sequence to study the role of Cx36 in these cells. Independent clones of MIN6 cells were obtained that had a markedly reduced Cx36 expression. Loss of Cx36 decreased functional gap junctional conductance in these clones. This alteration impaired the synchronization of glucose-induced [Ca 2+ ] i oscillations and insulin secretion in response to glucose, to secretagogues that increase [cAMP] i , and to depolarizing conditions. These data provide the first evidence that Cx36-made channels 1 ) mediate functional coupling in MIN6 cells, 2 ) provide for synchronous [Ca 2+ ] i oscillations, and 3 ) are necessary for proper insulin secretion in response to metabolizable and nonmetabolizable secretagogues. Footnotes Address correspondence and reprint requests to Alessandra Calabrese, Department of Morphology, University of Geneva, C.M.U., 1 rue Michel Servet, 1211 Geneva 4, Switzerland. E-mail: alessandra.calabrese{at}medecine.unige.ch . Received for publication 2 August 2002 and accepted in revised form 5 November 2002. [Ca 2+ ] i , cytoplasmic-free Ca 2+ ; FSK, forskolin; Gc, gap junctional conductance; IBMX, 3-isobutyl-1-methylxanthine; TEA, tetraethylammonium. DIABETES