UNIGE document Scientific Article
previous document  unige:35086  next document
add to browser collection

Desensitization of mitochondrial Ca2+ and insulin secretion responses in the beta cell

Published in The Journal of biological chemistry. 1998, vol. 273, no. 33, p. 20770-8
Abstract The role of mitochondria in the desensitization of insulin secretion was investigated. In rat pancreatic beta cells, both insulin secretion and mitochondrial [Ca2+] increases were desensitized following two challenges with the mitochondrial substrate methyl succinate. In the beta cell line INS-1, similar results were observed when a 5-min interval separated two 5-min pulses. In contrast, ATP generation monitored in luciferase-expressing INS-1 cells was stimulated to the same extent during both exposures to methyl succinate. Succinate, like alpha-glycerophosphate, activates the electron transport chain at complex II. As a consequence, the mitochondrial membrane hyperpolarizes, promoting ATP synthesis and Ca2+ influx into the mitochondria through the uniporter. The mitochondrial desensitization was further studied in permeabilized INS-1 cells. Increasing extramitochondrial [Ca2+] from 100 to 500 nM enhanced succinate oxidation 4-fold. At 500 nM Ca2+, 1 mM succinate caused a blunted mitochondrial [Ca2+] increase upon the second, compared with the first, stimulation. These effects were mimicked by alpha-glycerophosphate, and there was cross-desensitization between the two compounds. Succinate hyperpolarized the mitochondrial membrane during both the first and second applications. This suggests that the uniporter itself, rather than the respiratory chain, is desensitized. These results emphasize the key role of the mitochondria not only in the stimulation of insulin secretion, but also in its desensitization.
Keywords Adenosine Triphosphate/biosynthesisAnimalsCalcium/metabolismCarbon Dioxide/metabolismCell LineElectron Transport/drug effectsInsulin/metabolism/secretionIslets of Langerhans/cytology/metabolismMaleMitochondria/metabolismOxidation-ReductionRatsRats, WistarSuccinic Acid/metabolism
PMID: 9694821
Full text
Article (Published version) (259 Kb) - public document Free access
(ISO format)
MAECHLER, Pierre et al. Desensitization of mitochondrial Ca2+ and insulin secretion responses in the beta cell. In: The Journal of biological chemistry, 1998, vol. 273, n° 33, p. 20770-8. https://archive-ouverte.unige.ch/unige:35086

478 hits



Deposited on : 2014-03-28

Export document
Format :
Citation style :