Format

Send to

Choose Destination
Cell Calcium. 2014 Sep;56(3):235-43. doi: 10.1016/j.ceca.2014.07.011. Epub 2014 Aug 2.

Regulation of endogenous and heterologous Ca²⁺ release-activated Ca²⁺ currents by pH.

Author information

1
Queen's Center for Biomedical Research, Laboratory of Cell and Molecular Signaling, The Queen's Medical Center, Honolulu, HI 96813, United States; John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, United States; Department of Pharmacology and Toxicology, ZHMB, Saarland University, D-66421 Homburg, Germany.
2
Queen's Center for Biomedical Research, Laboratory of Cell and Molecular Signaling, The Queen's Medical Center, Honolulu, HI 96813, United States; John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, United States.
3
Queen's Center for Biomedical Research, Laboratory of Cell and Molecular Signaling, The Queen's Medical Center, Honolulu, HI 96813, United States; John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, United States. Electronic address: rpenner@hawaii.edu.
4
Queen's Center for Biomedical Research, Laboratory of Cell and Molecular Signaling, The Queen's Medical Center, Honolulu, HI 96813, United States; John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, United States; Department of Biophysics, Saarland University, ZHMB, 66421 Homburg, Germany. Electronic address: bpcpei@uks.eu.

Abstract

Deviations from physiological pH (∼pH 7.2) as well as altered Ca(2+) signaling play important roles in immune disease and cancer. One of the most ubiquitous pathways for cellular Ca(2+) influx is the store-operated Ca(2+) entry (SOCE) or Ca(2+) release-activated Ca(2+) current (ICRAC), which is activated upon depletion of intracellular Ca(2+) stores. We here show that extracellular and intracellular changes in pH regulate both endogenous ICRAC in Jurkat T lymphocytes and RBL2H3 cells, and heterologous ICRAC in HEK293 cells expressing the molecular components STIM1/2 and Orai1/2/3 (CRACM1/2/3). We find that external acidification suppresses, and alkalization facilitates IP3-induced ICRAC. In the absence of IP3, external alkalization did not elicit endogenous ICRAC but was able to activate heterologous ICRAC in HEK293 cells expressing Orai1/2/3 and STIM1 or STIM2. Similarly, internal acidification reduced IP3-induced activation of endogenous and heterologous ICRAC, while alkalization accelerated its activation kinetics without affecting overall current amplitudes. Mutation of two aspartate residues to uncharged alanine amino acids (D110/112A) in the first extracellular loop of Orai1 significantly attenuated both the inhibition of ICRAC by external acidic pH as well as its facilitation by alkaline conditions. We conclude that intra- and extracellular pH differentially regulates ICRAC. While intracellular pH might affect aggregation and/or binding of STIM to Orai, external pH seems to modulate ICRAC through its channel pore, which in Orai1 is partially mediated by residues D110 and D112.

KEYWORDS:

HEK293; I(CRAC); Jurkat cells; Orai; RBL; STIM; Whole-cell patch clamp

PMID:
25168908
PMCID:
PMC4162834
DOI:
10.1016/j.ceca.2014.07.011
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center