Wolf R A
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Am J Physiol. 1992 Nov;263(5 Pt 1):C1021-8. doi: 10.1152/ajpcell.1992.263.5.C1021.
Myocardial synthesis of phosphatidylinositol 4,5-bisphosphate (PIP2) is highly compartmentalized in the sarcolemmal membrane. Sarcolemmal vesicles contain endogenous phospholipase C (PLC), but the identity of sarcolemmal PLC and its relationship to soluble PLC have not been determined previously. Sarcolemmal and cytosolic PLC were prepared from canine myocardium and characterized by DEAE-cellulose chromatography and by immunoblotting with monoclonal and polyclonal antibodies to isoenzymes of PLC (PLC beta, PLC gamma, and PLC delta). DEAE-cellulose chromatography resolved two forms of cytosolic PLC that were identified as an 85-kDa form of PLC delta and a 145-kDa form of PLC gamma. In contrast, DEAE-cellulose chromatography resolved a single form of sarcolemmal PLC that was identified as an 85-kDa form of PLC delta. These data demonstrate that PLC gamma and PLC delta are expressed in canine myocardium and that an 85-kDa form of PLC delta is selectively associated with sites of PIP2 synthesis in a highly enriched preparation of sarcolemma. These data do not exclude the existence of additional isoenzymes of sarcolemmal PLC that may have been removed during isolation of sarcolemmal membranes.
心肌中磷脂酰肌醇4,5 - 二磷酸（PIP2）的合成在肌膜中高度区域化。肌膜囊泡含有内源性磷脂酶C（PLC），但肌膜PLC的身份及其与可溶性PLC的关系此前尚未确定。从犬心肌中制备了肌膜和胞质PLC，并通过DEAE - 纤维素色谱法以及用针对PLC同工酶（PLCβ、PLCγ和PLCδ）的单克隆和多克隆抗体进行免疫印迹来表征。DEAE - 纤维素色谱法分离出两种胞质PLC形式，分别鉴定为85 kDa的PLCδ形式和145 kDa的PLCγ形式。相比之下，DEAE - 纤维素色谱法分离出一种单一形式的肌膜PLC，鉴定为85 kDa的PLCδ形式。这些数据表明PLCγ和PLCδ在犬心肌中表达，并且在高度富集的肌膜制剂中，85 kDa的PLCδ形式与PIP2合成位点选择性相关。这些数据并不排除在肌膜分离过程中可能已被去除的其他肌膜PLC同工酶的存在。
