Molecular cloning and characterization of SCaMPER, a sphingolipid Ca2+ release-mediating protein from endoplasmic reticulum.
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.
Mao
C
C
Program in Molecular Medicine, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Kim
S H
SH
Almenoff
J S
JS
Rudner
X L
XL
Kearney
D M
DM
Kindman
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000235:genetics; D015640:Ion Channel Gating; D008562:Membrane Glycoproteins / Q000235:genetics; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D013107:Sphingolipids / Q000502:physiology; D014982:Xenopus laevis
D015220:Calcium Channels; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D013107:Sphingolipids; D002118:Calcium