Abstract
Transient receptor potential vanilloid 6 (TRPV6) channels play an important role in intestinal Ca2+ transport. These channels undergo Ca2+-induced inactivation. Here we show that Ca2+ flowing through these channels activates phospholipase C (PLC) leading to the depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) and formation of inositol 1,4,5-trisphosphate in TRPV6-expressing cells. PIP2 depletion was inhibited by the two structurally different PLC inhibitors 1-[6-[[17β-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U73122) and edelfosine. Ca2+-induced inactivation of TRPV6 was also prevented by the PLC inhibitors in whole-cell patch-clamp experiments. Ca2+ signals in TRPV6-expressing cells were transient upon restoration of extracellular Ca2+ but were rendered more sustained by the PLC inhibitors. Finally, intestinal Ca2+ transport in the everted duodenal sac assay was enhanced by edelfosine. These observations suggest that Ca2+-induced inactivation of TRPV6 limits intestinal Ca2+ absorption and raise the possibility that Ca2+ absorption can be enhanced pharmacologically by interfering with PLC activation.
Footnotes
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This work was supported by the National Institutes of Health National Institute of Neurological Disorders and Stroke [Grant NS055159]; the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant DK38961]; the National Institutes of Health National Institute on Aging [Grant AG297512]; the Alexander and Alexandrine Sinsheimer Foundation; and the University of Medicine and Dentistry of New Jersey Foundation.
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ABBREVIATIONS: TRPV6, transient receptor potential vanilloid 6; TRPV5, transient receptor potential vanilloid 5; TRPM8, transient receptor potential melastatin 8; TRPM4, transient receptor potential melastatin 4; PLC, phospholipase C; PIP2, phosphatidylinositol 4,5-bisphosphate; GFP, green fluorescent protein; CFP, cyan fluorescent protein; YFP, yellow fluorescent protein; PH, pleckstrin homology; NDF, nominally divalent-free; FRET, fluorescence resonance energy transfer; IP3, inositol 1,4,5-trisphosphate; U73122, 1-[6-[[17β-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione; HEK, human embryonic kidney; DMSO, dimethyl sulfoxide; U73343, 1-[6-[[17β-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-2,5-pyrrolidine-dione.
- Received October 7, 2008.
- Accepted December 10, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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Phospholipase C-Mediated Regulation of Transient Receptor Potential Vanilloid 6 Channels: Implications in Active Intestinal Ca2+ Transport
