title: Rapid turnover of phosphatidylinositol-4,5-bisphosphate in insulin-secreting cells mediated by Ca2+ and the ATP-to-ADP ratio.
abstract: Phosphatidylinositol-4,5-bisphosphate (PIP(2)) is important for a variety of cellular processes as a precursor for second messengers and by regulating ion channels, the cytoskeleton, and vesicle traffic in many types of cells, including insulin-secreting beta-cells. Here, we applied evanescent wave microscopy and the PIP(2)-binding pleckstrin homology domain from phospholipase C (PLC)-delta fused to the green fluorescent protein to characterize the regulation of plasma membrane PIP(2) in individual insulin-secreting MIN6 beta-cells. Elevation of the glucose concentration from 3 to 11 mmol/l evoked antisynchronous oscillations of [PIP(2)] and cytoplasmic Ca(2+)concentration, consistent with PLC being periodically activated by the voltage-dependent Ca(2+) influx. The effect of adenine nucleotides on [PIP(2)] was studied in cells permeabilized with alpha-toxin. ATP dose- dependently stimulated PIP(2) synthesis with half-maximal effect at 300 mumol/l. Omission of the nucleotide resulted in rapid loss of PIP(2) with t(1/2) < 40 s. ADP also stimulated PIP(2) formation, but this effect reflected local ATP formation and was prevented by the adenylate kinase inhibitor diadenosine-pentaphosphate. The ATP-induced PIP(2) synthesis was counteracted by the ADP analog adenosine-5'-O-2-thiodiphosphate. We conclude that plasma membrane PIP(2) is dynamically regulated by intracellular Ca(2+) and the ATP-to-ADP ratio in insulin-secreting cells. The rapid turnover allows maintenance of PIP(2) levels while generating second messengers of critical importance for insulin secretion.
authors.affiliation: Department of Medical Cell Biology, Uppsala University, Biomedical Centre, Box 571, SE-75123 Uppsala, Sweden.
authors.forename: Sophia
authors.initials: S
authors.lastname: Thore
authors.forename: Anne
authors.initials: A
authors.lastname: Wuttke
authors.forename: Anders
authors.initials: A
authors.lastname: Tengholm
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005947:Glucose; D006868:Hydrolysis; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D051379:Mice; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D005947:Glucose; D002118:Calcium