title: Phosphatidylinositol 4,5-bisphosphate enhances calcium release from sarcoplasmic reticulum of skeletal muscle.
abstract: In the course of our study on the function of sarcoplasmic reticulum (SR) in skeletal muscle, the stimulatory action of phosphatidylinositol 4,5-bisphosphate (PIP2) on the Ca2+ release from SR was demonstrated by using chemically skinned fibers and fragmented SR vesicles. PIP2 induced a tension spike followed by sustained contraction in skinned fibers. PIP2 enhanced the caffeine-induced Ca2+ release from SR vesicles at low concentrations and triggered Ca2+ release by itself at high concentrations. PIP2 also enhanced 45Ca2+ efflux from SR vesicles. However, inositol 1,4,5-triphosphate never produced these effects. The Ca2+-releasing action of PIP2 was only weakly affected by ruthenium red or procaine. These observations suggest that PIP2 activates an SR Ca2+ release channel whose properties are different from those of the Ca2+-induced Ca2+ release channel.
authors: Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
authors: M
authors: M
authors: Kobayashi
authors: A
authors: A
authors: Muroyama
authors: Y
authors: Y
authors: Ohizumi
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D009132:Muscles / Q000378:metabolism* / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000494:pharmacology*; D011343:Procaine / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D007295:Inositol Phosphates; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D015636:Magnesium Chloride; D012430:Ruthenium Red; D002110:Caffeine; D011343:Procaine; D015544:Inositol 1,4,5-Trisphosphate; D008274:Magnesium; D002118:Calcium