PIP sub( 2) in pancreatic beta -cells regulates voltage-gated calcium channels by a voltage-independent pathway

• Published in: American Journal of Physiology: Cell Physiology Vol. 311; no. 4; p. C630
• Main Authors: de la Cruz, Lizbeth, Puente, Erika I, Reyes-Vaca, Arturo, Arenas, Isabel, Garduno, Julieta, Bravo-Martinez, Jorge, Garcia, David E
• Format: Journal Article
• Language: English
• Published: 01.10.2016
• ISSN: 0363-6143

Phosphatidylinositol-4,5-bisphosphate (PIP sub( 2)) is a membrane phosphoinositide that regulates the activity of many ion channels. Influx of calcium primarily through voltage-gated calcium (Ca sub( V)) channels promotes insulin secretion in pancreatic beta -cells. However, whether Ca sub( V) channels are regulated by PIP sub( 2), as is the case for some non-insulin-secreting cells, is unknown. The purpose of this study was to investigate whether Ca sub( V) channels are regulated by PIP sub( 2) depletion in pancreatic beta -cells through activation of a muscarinic pathway induced by oxotremorine methiodide (Oxo-M). Ca sub( V) channel currents were recorded by the patch-clamp technique. The Ca sub( V) current amplitude was reduced by activation of the muscarinic receptor 1 (M sub( 1)R) in the absence of kinetic changes. The Oxo-M-induced inhibition exhibited the hallmarks of voltage-independent regulation and did not involve PKC activation. A small fraction of the Oxo-M-induced Ca sub( V) inhibition was diminished by a high concentration of Ca super( 2+) chelator, whereas greater than or equal to 50% of this inhibition was prevented by diC8-PIP sub( 2) dialysis. Localization of PIP sub( 2) in the plasma membrane was examined by transfecting INS-1 cells with PH-PLC delta 1, which revealed a close temporal association between PIP sub( 2) hydrolysis and Ca sub( V) channel inhibition. Furthermore, the depletion of PIP sub( 2) by a voltage-sensitive phosphatase reduced Ca sub( V) currents in a way similar to that observed following M sub( 1)R activation. These results indicate that activation of the M sub( 1)R pathway inhibits the Ca sub( V) channel via PIP sub( 2) depletion by a Ca sub( 2+)-dependent mechanism in pancreatic beta - and INS-1 cells and thereby support the hypothesis that membrane phospholipids regulate ion channel activity by interacting with ion channels.