Mao C, Kim S H, Almenoff J S, Rudner X L, Kearney D M, Kindman L A
Program in Molecular Medicine, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Proc Natl Acad Sci U S A. 1996 Mar 5;93(5):1993-6. doi: 10.1073/pnas.93.5.1993.
Release of Ca2+ stored in endoplasmic reticulum is a ubiquitous mechanism involved in cellular signal transduction, proliferation, and apoptosis. Recently, sphingolipid metabolites have been recognized as mediators of intracellular Ca2+ release, through their action at a previously undescribed intracellular Ca2+ channel. Here we describe the molecular cloning and characterization of a protein that causes the expression of sphingosyl-phosphocholine-mediated Ca2+ release when its complementary RNA is injected into Xenopus oocytes. SCaMPER (for sphingolipid Ca2+ release-mediating protein of endoplasmic reticulum) is an 181 amino acid protein with two putative membrane-spanning domains. SCaMPER is incorporated into microsomes upon expression in SO cells or after translation in vitro. It mediates Ca2+ release at 4 degrees C as well as 22 degrees C, consistent with having ion channel function. The EC50 for Ca2+ release from Xenopus oocytes is 40 microM, similar to sphingosyl-phosphocholine-mediated Ca2+ release from permeabilized mammalian cells. Because Ca2+ release is not blocked by ryanodine or La3+, the activity described here is distinct from the Ca2+ release activity of the ryanodine receptor and the inositol 1,4,5-trisphosphate receptor. The properties of SCaMPER are identical to those of the sphingolipid-gated Ca2+ channel that we have previously described. These findings suggest that SCaMPER is a sphingolipid-gated Ca2+-permeable channel and support its role as a mediator of this pathway for intracellular Ca2+ signal transduction.
内质网中储存的Ca2+释放是一种普遍存在的机制，参与细胞信号转导、增殖和凋亡。最近，鞘脂代谢产物已被认为是细胞内Ca2+释放的介质，通过它们作用于一个先前未描述的细胞内Ca2+通道。在这里，我们描述了一种蛋白质的分子克隆和特性，当将其互补RNA注射到非洲爪蟾卵母细胞中时，该蛋白质会导致鞘氨醇磷酸胆碱介导的Ca2+释放。SCaMPER（内质网鞘脂Ca2+释放介导蛋白）是一种含有两个假定跨膜结构域的181个氨基酸的蛋白质。SCaMPER在SO细胞中表达后或体外翻译后整合到微粒体中。它在4℃和22℃时均介导Ca2+释放，这与具有离子通道功能一致。从非洲爪蟾卵母细胞释放Ca2+的EC50为40μM，类似于从通透的哺乳动物细胞中鞘氨醇磷酸胆碱介导的Ca2+释放。由于Ca2+释放不受ryanodine或La3+的阻断，这里描述的活性不同于ryanodine受体和肌醇1,4,5-三磷酸受体的Ca2+释放活性。SCaMPER的特性与我们先前描述的鞘脂门控Ca2+通道的特性相同。这些发现表明SCaMPER是一种鞘脂门控的Ca2+通透通道，并支持其作为细胞内Ca2+信号转导这一途径的介质的作用。
