The catalytic activity of the CD45 membrane-proximal phosphatase domain is required for TCR signaling and regulation

EMBO J. 1994 Sep 1;13(17):4002-10.

Abstract

Cell surface expression of CD45, a receptor-like protein tyrosine phosphatase (PTPase), is required for T cell antigen receptor (TCR)-mediated signal transduction. Like the majority of transmembrane PTPases, CD45 contains two cytoplasmic phosphatase domains, whose relative in vivo function is not known. Site-directed mutagenesis of the individual catalytic residues of the two CD45 phosphatase domains indicates that the catalytic activity of the membrane-proximal domain is both necessary and sufficient for restoration of TCR signal transduction in a CD45-deficient cell. The putative catalytic activity of the distal phosphatase domain is not required for proximal TCR-mediated signaling events. Moreover, in the context of a chimeric PTPase receptor, the putative catalytic activity of the distal phosphatase domain is not required for ligand-induced negative regulation of PTPase function. We also demonstrate that the phosphorylation of the C-terminal tyrosine of Lck, a site of negative regulation, is reduced only when CD45 mutants with demonstrable in vitro phosphatase activity are introduced into the CD45-deficient cells. These results demonstrate that the phosphatase activity of CD45 is critical for TCR signaling, and for regulating the levels of C-terminal phosphorylated Lck molecules.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Catalysis
  • DNA Mutational Analysis
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism
  • Leukocyte Common Antigens / genetics
  • Leukocyte Common Antigens / metabolism*
  • Ligands
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • Molecular Sequence Data
  • Phosphorylation
  • Point Mutation
  • Protein Processing, Post-Translational
  • Protein Tyrosine Phosphatases / genetics
  • Protein Tyrosine Phosphatases / metabolism*
  • Protein-Tyrosine Kinases / metabolism
  • Receptors, Antigen, T-Cell / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / physiology*
  • Structure-Activity Relationship
  • Tyrosine / metabolism

Substances

  • Ligands
  • Receptors, Antigen, T-Cell
  • Recombinant Fusion Proteins
  • Tyrosine
  • ErbB Receptors
  • Protein-Tyrosine Kinases
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • Leukocyte Common Antigens
  • Protein Tyrosine Phosphatases