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  • 1.
    Abels, M.
    et al.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Riva, M.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Poon, W.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Bennet, H.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Nagaraj, V.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Isomaa, B.
    Folkhalsan Res Ctr, Helsinki, Finland.;Dept Social Serv & Hlth Care, Jacobstad, Finland..
    Tuomi, T.
    Folkhalsan Res Ctr, Helsinki, Finland.;Dept Med, Helsinki, Finland..
    Ahren, B.
    Lund Univ, Ctr Diabet, Lund, Sweden..
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Fex, M.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Renstrom, E.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Groop, L.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Lyssenko, V.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    Wierup, N.
    Lund Univ, Ctr Diabet, Malmo, Sweden..
    CART is a novel glucose-dependent peptide with antidiabetic actions in humans2015In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 58, no Suppl. 1, p. S279-S280Article in journal (Other academic)
  • 2.
    Alenkvist, Ida
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tian, Geng
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Li, Jia
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Mehrabanfar, Saba
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Jin, Yang
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Birnir, Bryndis
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Physiology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Welsh, Michael
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Absence of Shb impairs insulin secretion by elevated FAK activity in pancreatic islets2014In: Journal of Endocrinology, ISSN 0022-0795, E-ISSN 1479-6805, Vol. 223, no 3, p. 267-275Article in journal (Refereed)
    Abstract [en]

    The Src homology-2 domain containing protein B (SHB) has previously been shown to function as a pleiotropic adapter protein, conveying signals from receptor tyrosine kinases to intracellular signaling intermediates. The overexpression of Shb in β-cells promotes β-cell proliferation by increased insulin receptor substrate (IRS) and focal adhesion kinase (FAK) activity, whereas Shb deficiency causes moderate glucose intolerance and impaired first-peak insulin secretion. Using an array of techniques, including live-cell imaging, patch-clamping, immunoblotting, and semi-quantitative PCR, we presently investigated the causes of the abnormal insulin secretory characteristics in Shb-knockout mice. Shb-knockout islets displayed an abnormal signaling signature with increased activities of FAK, IRS, and AKT. β-catenin protein expression was elevated and it showed increased nuclear localization. However, there were no major alterations in the gene expression of various proteins involved in the β-cell secretory machinery. Nor was Shb deficiency associated with changes in glucose-induced ATP generation or cytoplasmic Ca(2) (+) handling. In contrast, the glucose-induced rise in cAMP, known to be important for the insulin secretory response, was delayed in the Shb-knockout compared with WT control. Inhibition of FAK increased the submembrane cAMP concentration, implicating FAK activity in the regulation of insulin exocytosis. In conclusion, Shb deficiency causes a chronic increase in β-cell FAK activity that perturbs the normal insulin secretory characteristics of β-cells, suggesting multi-faceted effects of FAK on insulin secretion depending on the mechanism of FAK activation.

  • 3.
    Chowdhury, Azazul Islam
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Sandler, Stellan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Bergsten, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Functional differences between aggregated and dispersed insulin-producing cells2013In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 56, no 7, p. 1557-1568Article in journal (Refereed)
    Abstract [en]

    Beta cells situated in the islet of Langerhans respond more vigorously to glucose than do dissociated beta cells. Mechanisms for this discrepancy were studied by comparing insulin-producing MIN6 cells aggregated into pseudoislets with MIN6 monolayer cells and mouse and human islets. MIN6 monolayers, pseudoislets and mouse and human islets were exposed to glucose, alpha-ketoisocaproic acid (KIC), pyruvate, KIC plus glutamine and the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 or wortmannin. Insulin secretion (ELISA), cytoplasmic Ca2+ concentration ([Ca2+](c); microfluorometry), glucose oxidation (radiolabelling), the expression of genes involved in mitochondrial metabolism (PCR) and the phosphorylation of insulin receptor signalling proteins (western blotting) were measured. Insulin secretory responses to glucose, pyruvate, KIC and glutamine were higher in pseudoislets than monolayers and comparable to those of human islets. Glucose oxidation and genes for mitochondrial metabolism were upregulated in pseudoislets compared with single cells and monolayers, respectively. Phosphorylation at the inhibitory S636/639 site of IRS-1 was significantly higher in monolayers and dispersed human and mouse cells than pseudoislets and intact human and mouse islets. PI3K inhibition only slightly attenuated glucose-stimulated insulin secretion from monolayers, but substantially reduced that from pseudoislets and human and mouse islets without suppressing the glucose-induced [Ca2+](c) response. We propose that islet architecture is critical for proper beta cell mitochondrial metabolism and IRS-1 signalling, and that PI3K regulates insulin secretion at a step distal to the elevation of [Ca2+](c).

  • 4. Dezaki, Katsuya
    et al.
    Damdindorj, Boldbaatar
    Sone, Hideyuki
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Gylfe, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Kurashina, Tomoyuki
    Yoshida, Masashi
    Kakei, Masafumi
    Yada, Toshihiko
    Ghrelin Attenuates cAMP-PKA Signaling to Evoke Insulinostatic Cascade in Islet beta-Cells2011In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 60, no 9, p. 2315-2324Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE-Ghrelin reportedly restricts insulin release in islet beta-cells via the G alpha(i2) subtype of G-proteins and thereby regulates glucose homeostasis. This study explored whether ghrelin regulates cAMP signaling and whether this regulation induces insulinostatic cascade in islet beta-cells. RESEARCH DESIGN AND METHODS-Insulin release was measured in rat perfused pancreas and isolated islets and cAMP production in isolated islets. Cytosolic cAMP concentrations ([cAMP](i)) were monitored in mouse MIN6 cells using evanescent-wave fluorescence imaging. In rat single beta-cells, cytosolic protein kinase-A activity ([PKA](i)) and Ca(2+) concentration ([Ca(2+)](i)) were measured by DR-II and fura-2 microfluorometry, respectively, and whole cell currents by patch-clamp technique. RESULTS-Ghrelin suppressed glucose (8.3 mmol/L)-induced insulin release in rat perfused pancreas and isolated islets, and these effects of ghrelin were blunted in the presence of cAMP analogs or adenylate cyclase inhibitor. Glucose-induced cAMP production in isolated islets was attenuated by ghrelin and enhanced by ghrelin receptor antagonist and anti-ghrelin antiserum, which counteract endogenous islet-derived ghrelin. Ghrelin inhibited the glucose-induced [cAMP](i) elevation and [PKA](i) activation in MIN6 and rat beta-cells, respectively. Furthermore, ghrelin potentiated voltage-dependent K(+) (Kv) channel currents without altering Ca(2+) channel currents and attenuated glucose-induced [Ca(2+)](i) increases in rat beta-cells in a PKA-dependent manner. CONCLUSIONS-Ghrelin directly interacts with islet beta-cells to attenuate glucose-induced cAMP production and PKA activation, which lead In activation of Kv channels and suppression of glucose-induced [Ca(2+)](i) increase and insulin release.

  • 5.
    Dyachok, O
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Sagetorp, J
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Isakov, Y
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, A
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    cAMP oscillations restrict protein kinase A redistribution in insulin-secreting cells.2006In: Biochem Soc Trans, ISSN 0300-5127, Vol. 34, no Pt 4, p. 498-501Article in journal (Refereed)
  • 6.
    Dyachok, Oleg
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Gylfe, Erik
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Ca2+-induced Ca2+ Release via Inositol 1,4,5-trisphosphate Receptors Is Amplified by Protein Kinase A and Triggers Exocytosis in Pancreatic β-Cells2004In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 279, no 44, p. 45455-45461Article in journal (Refereed)
    Abstract [en]

    Hormones, such as glucagon and glucagon-like peptide-1, potently amplify nutrient stimulated insulin secretion by raising cAMP. We have studied how cAMP affects Ca2+-induced Ca2+ release (CICR) in pancreatic β-cells from mice and rats and the role of CICR in secretion. CICR was observed as pronounced Ca2+ spikes on top of glucose- or depolarization-dependent rise of the cytoplasmic Ca2+ concentration ([Ca2+]i). cAMP-elevating agents strongly promoted CICR. This effect involved sensitization of the receptors underlying CICR, because many cells exhibited the characteristic Ca2+ spiking at low or even in the absence of depolarization-dependent elevation of [Ca2+]i. The cAMP effect was mimicked by a specific activator of protein kinase A in cells unresponsive to activators of cAMP-regulated guanine nucleotide exchange factor. Ryanodine pretreatment, which abolishes CICR mediated by ryanodine receptors, did not prevent CICR. Moreover, a high concentration of caffeine, known to activate ryanodine receptors independently of Ca2+, failed to mobilize intracellular Ca2+. On the contrary, a high caffeine concentration abolished CICR by interfering with inositol 1,4,5-trisphosphate receptors (IP3Rs). Therefore, the cell-permeable IP3R antagonist 2-aminoethoxydiphenyl borate blocked the cAMP-promoted CICR. Individual CICR events in pancreatic β-cells were followed by [Ca2+]i spikes in neighboring human erythroleukemia cells, used to report secretory events in the β-cells. The results indicate that protein kinase A-mediated promotion of CICR via IP3Rs is part of the mechanism by which cAMP amplifies insulin release.

  • 7.
    Dyachok, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Idevall-Hagren, Olof
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Sågetorp, Jenny
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tian, Geng
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Wuttke, Anne
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Arrieumerlou, Cecile
    Infection Biology, Biozentrum, University of Basel, Switzerland.
    Akusjärvi, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Gylfe, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Glucose-induced cyclic AMP oscillations regulate pulsatile insulin secretion2008In: Cell Metabolism, ISSN 1550-4131, E-ISSN 1932-7420, Vol. 8, no 1, p. 26-37Article in journal (Refereed)
    Abstract [en]

    Cyclic AMP (cAMP) and Ca2+ are key regulators of exocytosis in many cells, including insulin-secreting β-cells. Glucose-stimulated insulin secretion from β cells is pulsatile and involves oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i), but little is known about the detailed kinetics of cAMP signalling. Using evanescent-wave fluorescence imaging we found that glucose induces pronounced oscillations of cAMP in the sub-membrane space of single MIN6-cells and primary mouse β-cells. These oscillations were preceded and enhanced by elevations of [Ca2+]i. However, conditions raising cytoplasmic ATP could trigger cAMP elevations without accompanying [Ca2+]i rise, indicating that adenylyl cyclase activity may be controlled also by the substrate concentration. The cAMP oscillations correlated with pulsatile insulin release. Whereas elevation of cAMP enhanced secretion, inhibition of adenylyl cyclases suppressed both cAMP oscillations and pulsatile insulin release. We conclude that cell metabolism directly controls cAMP, and that glucose-induced cAMP oscillations regulate the magnitude and kinetics of insulin exocytosis.

  • 8.
    Dyachok, Oleg
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Isakov, Yegor
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Sågetorp, Jenny
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Oscillations of cyclic AMP in hormone-stimulated insulin-secreting beta-cells.2006In: Nature, ISSN 1476-4687, Vol. 439, no 7074, p. 349-52Article in journal (Refereed)
  • 9.
    Dyachok, Oleg
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Tufveson, Gunnar
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Surgical Sciences, Transplantation Surgery.
    Gylfe, Erik
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Ca2+-induced Ca2+ release by activation of inositol 1,4,5-trisphosphate receptors in primary pancreatic β-cells2004In: Cell Calcium, ISSN 0143-4160, E-ISSN 1532-1991, Vol. 36, no 1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    The effect of sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) inhibition on the cytoplasmic Ca2+ concentration ([Ca2+]i) was studied in primary insulin-releasing pancreatic β-cells isolated from mice, rats and human subjects as well as in clonal rat insulinoma INS-1 cells. In Ca2+-deficient medium the individual primary β-cells reacted to the SERCA inhibitor cyclopiazonic acid (CPA) with a slow rise of [Ca2+]i followed by an explosive transient elevation. The [Ca2+]i transients were preferentially observed at low intracellular concentrations of the Ca2+ indicator fura-2 and were unaffected by pre-treatment with 100 μM ryanodine. Whereas 20 mM caffeine had no effect on basal [Ca2+]i or the slow rise in response to CPA, it completely prevented the CPA-induced [Ca2+]i transients as well as inositol 1,4,5-trisphosphate-mediated [Ca2+]i transients in response to carbachol. In striking contrast to the primary β-cells, caffeine readily mobilized intracellular Ca2+ in INS-1 cells under identical conditions, and such mobilization was prevented by ryanodine pre-treatment. The results indicate that leakage of Ca2+ from the endoplasmic reticulum after SERCA inhibition is feedback-accelerated by Ca2+-induced Ca2+ release (CICR). In primary pancreatic β-cells this CICR is due to activation of inositol 1,4,5-trisphosphate receptors. CICR by ryanodine receptor activation may be restricted to clonal β-cells.

  • 10.
    Kononenko, Olga
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Bazov, Igor
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Watanabe, Hiroyuki
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Gerashchenko, Ganna
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Verbeek, Dineke S
    Alkass, Kanar
    Druid, Henrik
    Andersson, Malin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Mulder, Jan
    Svenningsen, Åsa Fex
    Rajkowska, Grazyna
    Stockmeier, Craig A
    Krishtal, Oleg
    Yakovleva, Tatiana
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Bakalkin, Georgy
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Opioid precursor protein isoform is targeted to the cell nuclei in the human brain2017In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1861, no 2, p. 246-255Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Neuropeptide precursors are traditionally viewed as proteins giving rise to small neuropeptide molecules. Prodynorphin (PDYN) is the precursor protein to dynorphins, endogenous ligands for the κ-opioid receptor. Alternative mRNA splicing of neuropeptide genes may regulate cell- and tissue-specific neuropeptide expression and produce novel protein isoforms. We here searched for novel PDYN mRNA and their protein product in the human brain.

    METHODS: Novel PDYN transcripts were identified using nested PCR amplification of oligo(dT) selected full-length capped mRNA. Gene expression was analyzed by qRT-PCR, PDYN protein by western blotting and confocal imaging, dynorphin peptides by radioimmunoassay. Neuronal nuclei were isolated using fluorescence-activated nuclei sorting (FANS) from postmortem human striatal tissue. Immunofluorescence staining and confocal microscopy was performed for human caudate nucleus.

    RESULTS: Two novel human PDYN mRNA splicing variants were identified. Expression of one of them was confined to the striatum where its levels constituted up to 30% of total PDYN mRNA. This transcript may be translated into ∆SP-PDYN protein lacking 13 N-terminal amino acids, a fragment of signal peptide (SP). ∆SP-PDYN was not processed to mature dynorphins and surprisingly, was targeted to the cell nuclei in a model cellular system. The endogenous PDYN protein was identified in the cell nuclei in human striatum by western blotting of isolated neuronal nuclei, and by confocal imaging.

    CONCLUSIONS AND GENERAL SIGNIFICANCE: High levels of alternatively spliced ∆SP-PDYN mRNA and nuclear localization of PDYN protein suggests a nuclear function for this isoform of the opioid peptide precursor in human striatum.

  • 11.
    Thore, Sophia
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Dyachok, Oleg
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Gylfe, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
    Feedback activation of phospholipase C via intracellular mobilization and store-operated influx of Ca2+ in insulin-secreting β-cells2005In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 118, no Pt 19, p. 4463-4471Article in journal (Refereed)
    Abstract [en]

    Phospholipase C (PLC) regulates various cellular processes by catalyzing the formation of inositol-1,4,5-trisphosphate (IP3) and diacylglycerol from phosphatidylinositol-4,5-bisphosphate (PIP2). Here, we have investigated the influence of Ca2+ on receptor-triggered PLC activity in individual insulin-secreting β-cells. Evanescent wave microscopy was used to record PLC activity using green fluorescent protein (GFP)-tagged PIP2/IP3-binding pleckstrin homology domain from PLCδ1, and the cytoplasmic Ca2+ concentration ([Ca2+]i) was simultaneously measured using the indicator Fura Red. Stimulation of MIN6 β-cells with the muscarinic-receptor agonist carbachol induced rapid and sustained PLC activation. By contrast, only transient activation was observed after stimulation in the absence of extracellular Ca2+ or in the presence of the non-selective Ca2+ channel inhibitor La3+. The Ca2+-dependent sustained phase of PLC activity did not require voltage-gated Ca2+ influx, as hyperpolarization with diazoxide or direct Ca2+ channel blockade with nifedipine had no effect. Instead, the sustained PLC activity was markedly suppressed by the store-operated channel inhibitors 2-APB and SKF96365. Depletion of intracellular Ca2+ stores with the sarco(endo)plasmic reticulum Ca2+-ATPase inhibitors thapsigargin or cyclopiazonic acid abolished Ca2+ mobilization in response to carbachol, and strongly suppressed the PLC activation in Ca2+-deficient medium. Analogous suppressions were observed after loading cells with the Ca2+ chelator BAPTA. Stimulation of primary mouse pancreatic β-cells with glucagon elicited pronounced [Ca2+]i spikes, reflecting protein kinase A-mediated activation of Ca2+-induced Ca2+ release via IP3 receptors. These [Ca2+]i spikes were found to evoke rapid and transient activation of PLC. Our data indicate that receptor-triggered PLC activity is enhanced by positive feedback from Ca2+ entering the cytoplasm from intracellular stores and via store-operated channels in the plasma membrane. Such amplification of receptor signalling should be important in the regulation of insulin secretion by hormones and neurotransmitters.

  • 12.
    Thore, Sophia
    et al.
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Dyachok, Oleg
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Tengholm, Anders
    Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Medical Cell Biology.
    Oscillations of Phospholipase C Activity Triggered by Depolarizatio and Ca2+ Influx in Insulin-secreting Cells2004In: The Journal of Biological Chemistry (JBC), Vol. 279, no 19, p. 19396-19400Article in journal (Refereed)
1 - 12 of 12
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