Essential role of phosphoinositide 3-kinase in leptin-induced KATP channel activation in the rat CRI-G1 insulinoma cell line

Jennie Harvey, Neil G. McKay, Kay S. Walker, Jeroen Van der Kaay, C. Peter Downes, Michael L. J. Ashford

    Research output: Contribution to journalArticle

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    Abstract

    The mechanism by which leptin increases ATP-sensitive K+ (KATP) channel activity was investigated using the insulin-secreting cell line, CRI-G1. Wortmannin and LY 294002, inhibitors of phosphoinositide 3-kinase (PI3-kinase), prevented activation of KATP channels by leptin. The inositol phospholipids phosphatidylinositol bisphosphate and phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) mimicked the effect of leptin by increasing KATP channel activity in whole-cell and inside-out current recordings. LY 294002 prevented phosphatidylinositol bisphosphate, but not PtdIns(3,4,5)P3, from increasing KATP channel activity, consistent with the latter lipid acting as a membrane-associated messenger linking leptin receptor activation and KATP channels. Signaling cascades, activated downstream from PI 3-kinase, utilizing PtdIns(3,4,5)P3 as a second messenger and commonly associated with insulin and cytokine action (MAPK, p70 ribosomal protein-S6 kinase, stress-activated protein kinase 2, p38 MAPK, and protein kinase B), do not appear to be involved in leptin-mediated activation of KATP channels in this cell line. Although PtdIns(3,4,5)P3 appears a plausible and attractive candidate for the messenger that couples KATP channels to leptin receptor activation, direct measurement of PtdIns(3,4,5)P3 demonstrated that insulin, but not leptin, increased global cellular levels of PtdIns(3,4,5)P3. Possible mechanisms to explain the involvement of PI 3-kinases in KATP channel regulation are discussed.

    Original languageEnglish
    Pages (from-to)4660-4669
    Number of pages10
    JournalJournal of Biological Chemistry
    Volume275
    Issue number7
    DOIs
    Publication statusPublished - 18 Feb 2000

    Fingerprint

    KATP Channels
    Insulinoma
    1-Phosphatidylinositol 4-Kinase
    Phosphatidylinositols
    Leptin
    Rats
    Phosphotransferases
    Chemical activation
    Cells
    Cell Line
    Leptin Receptors
    2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
    p38 Mitogen-Activated Protein Kinases
    Insulin
    Phosphatidylinositol 3-Kinases
    Mitogen-Activated Protein Kinase 11
    Ribosomal Protein S6 Kinases
    Proto-Oncogene Proteins c-akt
    Mitogen-Activated Protein Kinase Kinases
    Insulin-Secreting Cells

    Cite this

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    title = "Essential role of phosphoinositide 3-kinase in leptin-induced KATP channel activation in the rat CRI-G1 insulinoma cell line",
    abstract = "The mechanism by which leptin increases ATP-sensitive K+ (KATP) channel activity was investigated using the insulin-secreting cell line, CRI-G1. Wortmannin and LY 294002, inhibitors of phosphoinositide 3-kinase (PI3-kinase), prevented activation of KATP channels by leptin. The inositol phospholipids phosphatidylinositol bisphosphate and phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) mimicked the effect of leptin by increasing KATP channel activity in whole-cell and inside-out current recordings. LY 294002 prevented phosphatidylinositol bisphosphate, but not PtdIns(3,4,5)P3, from increasing KATP channel activity, consistent with the latter lipid acting as a membrane-associated messenger linking leptin receptor activation and KATP channels. Signaling cascades, activated downstream from PI 3-kinase, utilizing PtdIns(3,4,5)P3 as a second messenger and commonly associated with insulin and cytokine action (MAPK, p70 ribosomal protein-S6 kinase, stress-activated protein kinase 2, p38 MAPK, and protein kinase B), do not appear to be involved in leptin-mediated activation of KATP channels in this cell line. Although PtdIns(3,4,5)P3 appears a plausible and attractive candidate for the messenger that couples KATP channels to leptin receptor activation, direct measurement of PtdIns(3,4,5)P3 demonstrated that insulin, but not leptin, increased global cellular levels of PtdIns(3,4,5)P3. Possible mechanisms to explain the involvement of PI 3-kinases in KATP channel regulation are discussed.",
    author = "Jennie Harvey and McKay, {Neil G.} and Walker, {Kay S.} and {Van der Kaay}, Jeroen and Downes, {C. Peter} and Ashford, {Michael L. J.}",
    year = "2000",
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    language = "English",
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    Essential role of phosphoinositide 3-kinase in leptin-induced KATP channel activation in the rat CRI-G1 insulinoma cell line. / Harvey, Jennie; McKay, Neil G.; Walker, Kay S.; Van der Kaay, Jeroen ; Downes, C. Peter; Ashford, Michael L. J.

    In: Journal of Biological Chemistry, Vol. 275, No. 7, 18.02.2000, p. 4660-4669.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Essential role of phosphoinositide 3-kinase in leptin-induced KATP channel activation in the rat CRI-G1 insulinoma cell line

    AU - Harvey, Jennie

    AU - McKay, Neil G.

    AU - Walker, Kay S.

    AU - Van der Kaay, Jeroen

    AU - Downes, C. Peter

    AU - Ashford, Michael L. J.

    PY - 2000/2/18

    Y1 - 2000/2/18

    N2 - The mechanism by which leptin increases ATP-sensitive K+ (KATP) channel activity was investigated using the insulin-secreting cell line, CRI-G1. Wortmannin and LY 294002, inhibitors of phosphoinositide 3-kinase (PI3-kinase), prevented activation of KATP channels by leptin. The inositol phospholipids phosphatidylinositol bisphosphate and phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) mimicked the effect of leptin by increasing KATP channel activity in whole-cell and inside-out current recordings. LY 294002 prevented phosphatidylinositol bisphosphate, but not PtdIns(3,4,5)P3, from increasing KATP channel activity, consistent with the latter lipid acting as a membrane-associated messenger linking leptin receptor activation and KATP channels. Signaling cascades, activated downstream from PI 3-kinase, utilizing PtdIns(3,4,5)P3 as a second messenger and commonly associated with insulin and cytokine action (MAPK, p70 ribosomal protein-S6 kinase, stress-activated protein kinase 2, p38 MAPK, and protein kinase B), do not appear to be involved in leptin-mediated activation of KATP channels in this cell line. Although PtdIns(3,4,5)P3 appears a plausible and attractive candidate for the messenger that couples KATP channels to leptin receptor activation, direct measurement of PtdIns(3,4,5)P3 demonstrated that insulin, but not leptin, increased global cellular levels of PtdIns(3,4,5)P3. Possible mechanisms to explain the involvement of PI 3-kinases in KATP channel regulation are discussed.

    AB - The mechanism by which leptin increases ATP-sensitive K+ (KATP) channel activity was investigated using the insulin-secreting cell line, CRI-G1. Wortmannin and LY 294002, inhibitors of phosphoinositide 3-kinase (PI3-kinase), prevented activation of KATP channels by leptin. The inositol phospholipids phosphatidylinositol bisphosphate and phosphatidylinositol trisphosphate (PtdIns(3,4,5)P3) mimicked the effect of leptin by increasing KATP channel activity in whole-cell and inside-out current recordings. LY 294002 prevented phosphatidylinositol bisphosphate, but not PtdIns(3,4,5)P3, from increasing KATP channel activity, consistent with the latter lipid acting as a membrane-associated messenger linking leptin receptor activation and KATP channels. Signaling cascades, activated downstream from PI 3-kinase, utilizing PtdIns(3,4,5)P3 as a second messenger and commonly associated with insulin and cytokine action (MAPK, p70 ribosomal protein-S6 kinase, stress-activated protein kinase 2, p38 MAPK, and protein kinase B), do not appear to be involved in leptin-mediated activation of KATP channels in this cell line. Although PtdIns(3,4,5)P3 appears a plausible and attractive candidate for the messenger that couples KATP channels to leptin receptor activation, direct measurement of PtdIns(3,4,5)P3 demonstrated that insulin, but not leptin, increased global cellular levels of PtdIns(3,4,5)P3. Possible mechanisms to explain the involvement of PI 3-kinases in KATP channel regulation are discussed.

    U2 - 10.1074/jbc.275.7.4660

    DO - 10.1074/jbc.275.7.4660

    M3 - Article

    VL - 275

    SP - 4660

    EP - 4669

    JO - Journal of Biological Chemistry

    JF - Journal of Biological Chemistry

    SN - 0021-9258

    IS - 7

    ER -