Biochemical analysis of interleukin-2 receptor beta chain phosphorylation by p56(lck)

Tyrosine phosphorylation of multiple proteins, including the receptor itsel f, is an initial event in IL-2 signaling and leads to recruitment of SH2 or PTB domain-containing proteins to the receptor. In this study, we have use d subdomains of the IL-2 receptor beta chain (IL-2R beta) expressed in Esch erichia coli as GST fusion proteins to identify the tyrosine residues that could be phosphorylated by p56(lck), one of the critical tyrosine kinases a ctivated by IL-2, We report that recombinant p56(lck) phosphorylates in vit ro tyrosine residues within the IL-2R beta chain but not those within the I L-2R gamma chain. p56(lck) phosphorylates tyrosine residues 355, 358 and 36 1 but not 338 of the IL-2R beta chain acidic subdomain. Interestingly, phos phorylation of Tyr-358 appears to require the presence of either Tyr-355 or Tyr-361, p56(lck) also phosphorylates very efficiently the two tyrosines p resent in the IL-2R beta chain C-terminal region, Tyr-392 and Tyr-510, We a lso investigated the association of p56(lck) with the IL-2R beta chain whic h was found to depend on a short stretch of the IL-2R beta chain acidic sub domain, and to be independent of the presence of its tyrosine residues. (C) 1999 Federation of European Biochemical Societies.