ORAI1, STIM1/2, and RYR1 shape subsecond Ca 2+ microdomains upon T cell activation

Sci Signal. 2018 Dec 18;11(561):eaat0358. doi: 10.1126/scisignal.aat0358.

Abstract

The earliest intracellular signals that occur after T cell activation are local, subsecond Ca2+ microdomains. Here, we identified a Ca2+ entry component involved in Ca2+ microdomain formation in both unstimulated and stimulated T cells. In unstimulated T cells, spontaneously generated small Ca2+ microdomains required ORAI1, STIM1, and STIM2. Super-resolution microscopy of unstimulated T cells identified a circular subplasmalemmal region with a diameter of about 300 nm with preformed patches of colocalized ORAI1, ryanodine receptors (RYRs), and STIM1. Preformed complexes of STIM1 and ORAI1 in unstimulated cells were confirmed by coimmunoprecipitation and Förster resonance energy transfer studies. Furthermore, within the first second after T cell receptor (TCR) stimulation, the number of Ca2+ microdomains increased in the subplasmalemmal space, an effect that required ORAI1, STIM2, RYR1, and the Ca2+ mobilizing second messenger NAADP (nicotinic acid adenine dinucleotide phosphate). These results indicate that preformed clusters of STIM and ORAI1 enable local Ca2+ entry events in unstimulated cells. Upon TCR activation, NAADP-evoked Ca2+ release through RYR1, in coordination with Ca2+ entry through ORAI1 and STIM, rapidly increases the number of Ca2+ microdomains, thereby initiating spread of Ca2+ signals deeper into the cytoplasm to promote full T cell activation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Signaling
  • Cell Membrane
  • Cells, Cultured
  • Female
  • Fluorescence Resonance Energy Transfer
  • Lymphocyte Activation*
  • Male
  • Membrane Microdomains / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • ORAI1 Protein / metabolism*
  • Ryanodine Receptor Calcium Release Channel / metabolism*
  • Stromal Interaction Molecule 1 / metabolism*
  • Stromal Interaction Molecule 2 / metabolism*
  • T-Lymphocytes / cytology*
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism

Substances

  • ORAI1 Protein
  • Orai1 protein, mouse
  • Ryanodine Receptor Calcium Release Channel
  • Stim1 protein, mouse
  • Stim2 protein, mouse
  • Stromal Interaction Molecule 1
  • Stromal Interaction Molecule 2
  • ryanodine receptor 1, mouse
  • Calcium