Properties of Ca Currents Activated by T Cell Receptor Signaling
Influx of extracellular Ca is one of the early biochemical events associated with signaling through the T cell receptor (TCR) complex1–4. The influx of Ca is a critical component of the signaling pathway because it helps to drive the cytoplasmic Ca from resting levels of around 100 nM up to several μM, the concentration required for activation of many intracellular Ca binding proteins and enzymes5. Recently there has been a great deal of progress in understanding the molecular basis of the very earliest events in TCR signaling which precede Ca mobilization as well as those later Ca-dependent processes leading to transcription of the IL-2 gene6–9. Unfortunately, the molecules involved in initiation, maintenance, and termination of Ca influx remain elusive despite the combined efforts of researchers using molecular, biochemical and electrophysiological approaches. However, during the last year a number of important discoveries have generated an unprecedented interest in the nature of the Ca influx pathway10,11.
KeywordsInositol Phosphate Diffusible Messenger Cell Antigen Receptor Signal Transduction
Unable to display preview. Download preview PDF.
- 25.B.A. Premack, T.V. McDonald and P. Gardner, Activation of Ca currents in a Jurkat T cells following the depletion of Ca stores by microsomal Ca-ATPase inhibitors, In press: J. Immunol. (1994).Google Scholar
- 28.H. Takemura, A.R. Hughes, O. Thastrup and J.J. Putney, Activation of calcium entry by the tumor promoter thapsigargin in parotid acinar cells. Evidence that an intracellular calcium pool and not an inositol phosphate regulates calcium fluxes at the plasma membrane, J. Biol. Chem. 264: 12266 (1989).PubMedGoogle Scholar
- 29.H. Gouy, D. Cefai, S.B. Christensen, P. Debre and G. Bismuth, Ca influx in human T lymphocytes is induced independently of inositol phosphate production by mobilization of intracellular Ca stores. A study with the Ca endoplasmic reticulum-ATPase inhibitor thapsigargin, Eur. J. Immunol. 20: 2269 (1990).PubMedCrossRefGoogle Scholar
- 33.J. Llopis, S.B. Chow, G.E. Kass, A. Gahm and S. Orrenius, Comparison between the effects of the microsomal Ca-translocase inhibitors thapsigargin and 2,5-di-(tert-butyl)-l,4-benzohydroquinone on cellular calcium fluxes Comparison between the effects of the microsomal Ca-translocase inhibitors thapsigargin and 2,5-di-(tert-butyl)-l,4-benzohydroquinone on cellular calcium fluxes, Biochem. J. 553 (1991).Google Scholar
- 36.W. Aimers and E.W. McCleskey, Nonselective conductance in calcium channels of frog muscle: Calcium selectivity in a single-file pore, J. Physiol. 353: 585 (1984).Google Scholar