Phospholipase C-gamma1 is required for the activation of store-operated Ca2+ channels in liver cells.
Repetitive hormone-induced changes in concentration of free cytoplasmic Ca2+ in hepatocytes require Ca2+ entry through receptor-activated Ca2+ channels and SOCs (store-operated Ca2+ channels). SOCs are activated by a decrease in Ca2+ concentration in the intracellular Ca2+ stores, but the molecular components and mechanisms are not well understood. Some studies with other cell types suggest that PLC-gamma (phospholipase C-gamma) is involved in the activation of receptor-activated Ca2+ channels and/or SOCs, independently of PLC-gamma-mediated generation of IP3 (inositol 1,4,5-trisphosphate). The nature of the Ca2+ channels regulated by PLC-gamma has not been defined clearly. The aim of the present study was to determine if PLC-gamma is required for the activation of SOCs in liver cells. Transfection of H4IIE cells derived from rat hepatocytes with siRNA (short interfering RNA) targeted to PLC-gamma1 caused a reduction (by approx. 70%) in the PLC-gamma1 protein expression, with maximal effect at 72-96 h. This was associated with a decrease (by approx. 60%) in the amplitude of the I(SOC) (store-operated Ca2+ current) developed in response to intracellular perfusion with either IP(3) or thapsigargin. Knockdown of STIM1 (stromal interaction molecule type 1) by siRNA also resulted in a significant reduction (approx. 80% at 72 h post-transfection) of the I(SOC) amplitude. Immunoprecipitation of PLC-gamma1 and STIM1, however, suggested that under the experimental conditions these proteins do not interact with each other. It is concluded that the PLC-gamma1 protein, independently of IP3 generation and STIM1, is required to couple endoplasmic reticulum Ca2+ release to the activation of SOCs in the plasma membrane of H4IIE liver cells.
Litjens
Tom
T
School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia 5005, Australia.
Nguyen
Than
T
Castro
Joel
J
Aromataris
Edoardo C
EC
Jones
Lynette
L
Barritt
Greg J
GJ
Rychkov
Grigori Y
GY
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004075:Diglycerides / Q000378:metabolism / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D022781:Hepatocytes / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D051966:Phospholipase C gamma / Q000502:physiology*; D011760:Pyrrolidinones / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D015220:Calcium Channels; D004075:Diglycerides; D004963:Estrenes; D008562:Membrane Glycoproteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D011760:Pyrrolidinones; D034741:RNA, Small Interfering; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; C038237:1-oleoyl-2-acetylglycerol; D051966:Phospholipase C gamma; D002118:Calcium