Bidirectional coupling between ryanodine receptors and Ca2+ release-activated Ca2+ (CRAC) channel machinery sustains store-operated Ca2+ entry in human T lymphocytes

J Biol Chem. 2012 Oct 26;287(44):37233-44. doi: 10.1074/jbc.M112.398974. Epub 2012 Sep 4.

Abstract

The expression and functional significance of ryanodine receptors (RyR) were investigated in resting and activated primary human T cells. RyR1, RyR2, and RyR3 transcripts were detected in human T cells. RyR1/2 transcript levels increased, whereas those of RyR3 decreased after T cell activation. RyR1/2 protein immunoreactivity was detected in activated but not in resting T cells. The RyR agonist caffeine evoked Ca(2+) release from the intracellular store in activated T cells but not in resting T cells, indicating that RyR are functionally up-regulated in activated T cells compared with resting T cells. In the presence of store-operated Ca(2+) entry (SOCE) via plasmalemmal Ca(2+) release-activated Ca(2+) (CRAC) channels, RyR blockers reduced the Ca(2+) leak from the endoplasmic reticulum (ER) and the magnitude of SOCE, suggesting that a positive feedback relationship exists between RyR and CRAC channels. Overexpression of fluorescently tagged RyR2 and stromal interaction molecule 1 (STIM1), an ER Ca(2+) sensor gating CRAC channels, in HEK293 cells revealed that RyR are co-localized with STIM1 in the puncta formed after store depletion. These data indicate that in primary human T cells, the RyR are coupled to CRAC channel machinery such that SOCE activates RyR via a Ca(2+)-induced Ca(2+) release mechanism, which in turn reduces the Ca(2+) concentration within the ER lumen in the vicinity of STIM1, thus facilitating SOCE by reducing store-dependent CRAC channel inactivation. Treatment with RyR blockers suppressed activated T cell expansion, demonstrating the functional importance of RyR in T cells.

MeSH terms

  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / metabolism
  • Calcium Signaling*
  • Cell Proliferation
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism
  • Gene Expression
  • HEK293 Cells
  • Humans
  • Jurkat Cells
  • Lymphocyte Activation
  • Membrane Proteins / metabolism
  • Neoplasm Proteins / metabolism
  • Ryanodine Receptor Calcium Release Channel / genetics
  • Ryanodine Receptor Calcium Release Channel / metabolism*
  • Stromal Interaction Molecule 1
  • T-Lymphocytes / metabolism*
  • T-Lymphocytes / physiology
  • Up-Regulation

Substances

  • Calcium Channel Blockers
  • Calcium Channels
  • Membrane Proteins
  • Neoplasm Proteins
  • Ryanodine Receptor Calcium Release Channel
  • STIM1 protein, human
  • Stromal Interaction Molecule 1
  • Calcium