Cohen J S, Brown H A
Department of Molecular Medicine, Veterinary Medical Center, and Field of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York 14853-6401, USA.
Biochemistry. 2001 Jun 5;40(22):6589-97. doi: 10.1021/bi0103011.
Roles for glycerophospholipids in exocytosis have been proposed, but remain controversial. Phospholipases are stimulated following the activation of the high-affinity receptor for immunoglobulin E (IgE) in mast cells. To study the biochemical sequelae that lead to degranulation, broken cell systems were employed. We demonstrate that the addition of three distinct types of exogenous phospholipases (i.e., bcPLC, scPLD, and tfPLA(2)), all of which hydrolyze phosphatidylcholine (PC), trigger degranulation in permeabilized RBL-2H3 cells, a mucosal mast cell line. Production of bioactive lipids by these phospholipases promotes release of granule contents through the plasma membrane and acts downstream of PKC, PIP(2), and Rho subfamily GTPases in regulated secretion. These exogenous phospholipase-induced degranulation pathways circumvent specific factors activated following stimulation of the IgE receptor as well as in ATP- and GTP-dependent intracellular pathways. Taken together, these results suggest that regulated secretion may be achieved in vitro in the absence of cytosolic factors via phospholipase activation and that products of PC hydrolysis can promote exocytosis in mast cells.
甘油磷脂在胞吐作用中的作用已被提出，但仍存在争议。肥大细胞中免疫球蛋白E（IgE）的高亲和力受体激活后，磷脂酶会被刺激。为了研究导致脱颗粒的生化后遗症，采用了破碎细胞系统。我们证明，添加三种不同类型的外源性磷脂酶（即bcPLC、scPLD和tfPLA(2)），它们都能水解磷脂酰胆碱（PC），可触发透化的RBL-2H3细胞（一种黏膜肥大细胞系）脱颗粒。这些磷脂酶产生的生物活性脂质通过质膜促进颗粒内容物的释放，并在调节性分泌中作用于蛋白激酶C（PKC）、磷脂酰肌醇-4,5-二磷酸（PIP(2)）和Rho亚家族鸟苷三磷酸酶（GTPases）的下游。这些外源性磷脂酶诱导的脱颗粒途径绕过了IgE受体刺激后以及ATP和GTP依赖的细胞内途径中激活的特定因子。综上所述，这些结果表明，在没有细胞溶质因子的情况下，通过磷脂酶激活可能在体外实现调节性分泌，并且PC水解产物可以促进肥大细胞的胞吐作用。
