Lupu V D, Kaznacheyeva E, Krishna U M, Falck J R, Bezprozvanny I
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
J Biol Chem. 1998 Jun 5;273(23):14067-70. doi: 10.1074/jbc.273.23.14067.
The inositol 1,4,5-trisphosphate receptor (InsP3R) plays a key role in intracellular Ca2+ signaling. InsP3R is activated by InsP3 produced from phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C cleavage. Using planar lipid bilayer reconstitution technique, we demonstrate here that rat cerebellar InsP3R forms a stable inhibitory complex with endogenous PIP2. Disruption of InsP3R-PIP2 interaction by specific anti-PIP2 monoclonal antibody resulted in 3-4-fold increase in InsP3R activity and 10-fold shift in apparent affinity for InsP3. Exogenously added PIP2 blocks InsP3 binding to InsP3R and inhibits InsP3R activity. Similar results were obtained with a newly synthesized water soluble analog of PIP2, dioctanoyl-(4,5)PIP2, indicating that insertion of PIP2 into membrane is not required to exert its inhibitory effects on the InsP3R. We hypothesize that the functional link between InsP3R and PIP2 described in the present report provides a basis for a local, rapid, and efficient coupling between phospholipase C activation, PIP2 hydrolysis, and intracellular Ca2+ wave initiation in neuronal and non-neuronal cells.
肌醇1,4,5-三磷酸受体（InsP3R）在细胞内Ca2+信号传导中起关键作用。InsP3R由磷脂酶C切割磷脂酰肌醇4,5-二磷酸（PIP2）产生的InsP3激活。利用平面脂质双层重组技术，我们在此证明大鼠小脑InsP3R与内源性PIP2形成稳定的抑制复合物。用特异性抗PIP2单克隆抗体破坏InsP3R-PIP2相互作用导致InsP3R活性增加3-4倍，对InsP3的表观亲和力发生10倍的偏移。外源添加的PIP2可阻断InsP3与InsP3R的结合并抑制InsP3R活性。用新合成的PIP2水溶性类似物二辛酰基-（4,5）PIP2也得到了类似结果，表明PIP2插入膜中并非其对InsP3R发挥抑制作用所必需。我们推测本报告中描述的InsP3R与PIP2之间的功能联系为神经元和非神经元细胞中磷脂酶C激活、PIP2水解和细胞内Ca2+波起始之间的局部、快速和有效偶联提供了基础。
