Transient Tyrosine Phosphorylation of Human Ryanodine Receptor upon T Cell Stimulation

Abstract

The ryanodine receptor of Jurkat T lymphocytes was phosphorylated on tyrosine residues upon stimulation of the cells via the T cell receptor/CD3 complex. The tyrosine phosphorylation was transient, reaching a maximum at 2 min, and rapidly declined thereafter. In co-immunoprecipitates of the ryanodine receptor, the tyrosine kinases p56lck and p59fyn were detected. How. ever, only p59fyn associated with the ryanodine receptor in a stimulation-dependent fashion. Both tyrosine kinases, recombinantly expressed as glutathione S-transferase (GST) fusion proteins, phosphorylated the immu. noprecipitated ryanodine receptor in vitro. In permeabilized Jurkat T cells, GST-p59fyn, but not GST-p56 lck, GST-Grb2, or GST alone, significantly and concentration-dependently enhanced Ca2+ release by cyclic ADP-ribose. The tyrosine kinase inhibitor PP2 specifically blocked the effect of GST-p59fyn. This indicates that intracellular Ca2+ release via ryanodine receptors may be modulated by tyrosine phosphorylation during T cell activation.