Protein kinase C-induced phosphorylation of Orai1 regulates the intracellular Ca2+ level via the store-operated Ca2+ channel.
Ca(2+) signals through store-operated Ca(2+) (SOC) channels, activated by the depletion of Ca(2+) from the endoplasmic reticulum, regulate various physiological events. Orai1 is the pore-forming subunit of the Ca(2+) release-activated Ca(2+) (CRAC) channel, the best characterized SOC channel. Orai1 is activated by stromal interaction molecule (STIM) 1, a Ca(2+) sensor located in the endoplasmic reticulum. Orai1 and STIM1 are crucial for SOC channel activation, but the molecular mechanisms regulating Orai1 function are not fully understood. In this study, we demonstrate that protein kinase C (PKC) suppresses store-operated Ca(2+) entry (SOCE) by phosphorylation of Orai1. PKC inhibitors and knockdown of PKCbeta both resulted in increased Ca(2+) influx. Orai1 is strongly phosphorylated by PKC in vitro and in vivo at N-terminal Ser-27 and Ser-30 residues. Consistent with these results, substitution of endogenous Orai1 with an Orai1 S27A/S30A mutant resulted in increased SOCE and CRAC channel currents. We propose that PKC suppresses SOCE and CRAC channel function by phosphorylation of Orai1 at N-terminal serine residues Ser-27 and Ser-30.
Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe 657-8501, Japan.
Takumi
T
Kawasaki
Takehiko
T
Ueyama
Ingo
I
Lange
Stefan
S
Feske
Naoaki
N
Saito
D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D000071740:ORAI1 Protein; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D016133:Polymerase Chain Reaction; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D064546:Protein Kinase C beta; D000071737:Stromal Interaction Molecule 1
D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D002118:Calcium