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- Arkhammar, P., et al.
(författare)
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Protein kinase C modulates the insulin secretory process by maintaining a proper function of the beta-cell voltage-activated Ca2+ channels
- 1994
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Ingår i: Journal of Biological Chemistry. - : Baishideng Publishers. - 0021-9258 .- 1083-351X. ; 269:4, s. 2743-2749
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Tidskriftsartikel (refereegranskat)abstract
- 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. There was,h owever, no effect on thet otal amounts of hormone released. The present study con- firms that PKC has multiple roles and thereby interacta at different sites in the complex series of events consti- tuting the #?-cell signal-transduction pathway. It is sug- gested that PKC may be tonically active and effective in the maintenance of the phosphorylation state of the voltage-gated L-type Ca2+ channel, enabling an appro- priate function of this channel in the insulin secretory process.
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| 2. |
- Ljung, Rolf, et al.
(författare)
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40K glycoPEGylated, recombinant FVIIa: 3-month, double-blind, randomized trial of safety, pharmacokinetics, and preliminary efficacy in hemophilia patients with inhibitors.
- 2013
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 11:7, s. 1260-1268
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: A 40K glycoPEGylated, recombinant Factor VIIa (rFVIIa) bypassing agent (N7-GP) with a prolonged half-life (15 h) compared to rFVIIa was developed as a potential candidate for bleed preventive regimens in patients with hemophilia and inhibitors. OBJECTIVES: To evaluate the safety, pharmacokinetics, and preliminary efficacy of multiple doses of N7-GP in congenital hemophilia A and B patients with high-titer inhibitors. PATIENTS/METHODS: In this global, prospective, randomized, double-blinded, phase 2 trial, 25, 100, or 200 μg kg(-1) N7-GP was administered intravenously once every second day during a 3-month bleed preventive regimen and compared with a preceding 3-month observation period with on-demand treatment of bleeds with rFVIIa. The primary endpoint was adverse events; secondary endpoints were evaluation of immunogenicity, pharmacokinetics, and efficacy. RESULTS AND CONCLUSIONS: Overall, 23 patients were randomized and dosed (n = 8/7/8 for 25/100/200 μg kg(-1) ). N7-GP was well tolerated, with a low frequency of adverse events. No serious adverse events, immunogenic or thromboembolic events related to N7-GP were reported. The pharmacokinetic properties of N7-GP were similar to those reported in phase 1. The annualized bleeding rate (ABR) decreased in the treatment period vs. the observation period at all N7-GP dose levels. However, a dose-response relationship in the reduction could not be established in the N7-GP dose range evaluated. The ABR was also reduced at two dose levels during the last part of the observation period, and increased notably in the follow-up period irrespective of previous N7-GP dose. The trial was registered at ClinicalTrials.gov (Registration Number: NCT00951405). This article is protected by copyright. All rights reserved.
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| 8. |
- ZAITSEV, SV, et al.
(författare)
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Dissociation between changes in cytoplasmic free Ca2+ concentration and insulin secretion as evidenced from measurements in mouse single pancreatic islets
- 1995
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 92:21, s. 9712-9716
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous measurements of cytosolic free Ca2+ concentration and insulin release, in mouse single pancreatic islets, revealed a direct correlation only initially after stimulation with glucose or K+. Later, there is an apparent dissociation between these two parameters, with translocation of alpha and epsilon isoenzymes of protein kinase C to membranes and simultaneous desensitization of insulin release in response to glucose. Recovery of insulin release, without any concomitant changes in cytosolic free Ca2+ concentration, after addition of phorbol 12-myristate 13-acetate, okadaic acid, and forskolin supports the notion that the desensitization process is accounted for by dephosphorylation of key regulatory sites of the insulin exocytotic machinery.
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