Change search
ReferencesLink to record
Permanent link

Direct link
Protein kinase C modulates the insulin secretory process by maintaining a proper function of the beta-cell voltage-activated Ca2+ channels.
Show others and affiliations
1994 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 269, no 4, 2743-2749 p.Article in journal (Refereed) Published
Abstract [en]

In the present study an attempt was made to further elucidate the molecular mechanisms whereby protein kinase C (PKC) modulates the beta-cell stimulus-secretion coupling. Regulation of Ca2+ channel activity, [Ca2+]i, and insulin release were investigated in both normal pancreatic mouse beta-cells and in similar beta-cells deprived of PKC activity. [Ca2+]i was measured with the intracellular fluorescent Ca2+ indicator fura-2 and the Ca2+ channel activity was estimated by the whole cell configuration of the patch-clamp technique. To reveal the various isoenzymes of PKC present in the mouse beta-cell, proteins were separated by one-dimensional gel electrophoresis and Western blotting was performed. The production of inositol phosphates was measured by ion-exchange chromatography and insulin release was measured radioimmunologically. Acute stimulation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate resulted in suppression of both the carbamylcholine-induced increase in [Ca2+]i and production of inositol 1,4,5-trisphosphate. Under these conditions the increase in [Ca2+]i in response to glucose was similar to that found in control cells. When beta-cells were deprived of PKC, by exposure to 200 nM 12-O-tetradecanoylphorbol-13-acetate for 24-48 h, there was an enhanced response to carbamylcholine. This response constituted increases in both the [Ca2+]i signal and production of inositol 1,4,5-trisphosphate. Interestingly, cells with down-regulated PKC activity responded more slowly to glucose stimulation, when comparing the initial increase in [Ca2+]i, than control cells. On the other hand, the maximal increase in [Ca2+]i was similar whether or not PKC was present. Moreover, PKC down-regulated cells exhibited a significant reduction of maximal whole cell Ca2+ currents, a finding that may explain the altered kinetics with regard to the [Ca2+]i increase in response to the sugar. Both the alpha and beta 1 forms of the PKC isoenzymes were present in the mouse beta-cell and were also subjected to PKC down-regulation. Hence, either of these isoenzymes or both may be involved in the modulation of phospholipase C and Ca2+ channel activity. Since insulin release under physiological conditions is critically dependent on Ca(2+)-influx through the voltage-gated L-type Ca2+ channels, the kinetics of hormone release was expected to demonstrate a similar delay as that of the [Ca2+]i increase. Although not as pronounced, such a delay was indeed also observed in the onset of insulin release. There was, however, no effect on the total amounts of hormone released.(ABSTRACT TRUNCATED AT 400 WORDS)

Place, publisher, year, edition, pages
1994. Vol. 269, no 4, 2743-2749 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:kau:diva-29810PubMedID: 8300606OAI: oai:DiVA.org:kau-29810DiVA: diva2:657580
Available from: 2013-10-20 Created: 2013-10-20 Last updated: 2013-11-07Bibliographically approved

Open Access in DiVA

No full text

PubMed

Search in DiVA

By author/editor
Nånberg, Eewa
In the same journal
Journal of Biological Chemistry
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 19 hits
ReferencesLink to record
Permanent link

Direct link