期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 284, 期 29, 页码 19164-19168出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.C109.010900
关键词
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资金
- Pennsylvania Department of Health
- American Heart Association [0730184N]
- National Institutes of Health [AI058173]
STIM1 and STIM2 are dynamic transmembrane endoplasmic reticulum Ca2+ sensors, coupling directly to activate plasma membrane Orai Ca2+ entry channels. Despite extensive sequence homology, the STIM proteins are functionally distinct. We reveal that the short variable N-terminal random coil sequences of STIM1 and STIM2 confer profoundly different activation properties. Using Orai1-expressing HEK293 cells, chimeric replacement of the 43-amino-acid STIM1 N terminus with that of STIM2 attenuates Orai1-mediated Ca2+ entry and drastically slows store-induced Orai1 channel activation. Conversely, the 55-amino-acid STIM2 terminus substituted within STIM1 strikingly enhances both Orai1-mediated Ca2+ entry and constitutive coupling to activate Orai1 channels. Hence, STIM N termini are powerful coupling modifiers, functioning in STIM2 to brake the otherwise constitutive activation of Orai1 channels afforded by its high sensitivity to luminal Ca2+.
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