Inhibition of TCR/CD3-mediated signaling by a mutant of the hematopoietically expressed G16 GTP-binding protein

Eur J Immunol. 1998 May;28(5):1645-55. doi: 10.1002/(SICI)1521-4141(199805)28:05<1645::AID-IMMU1645>3.0.CO;2-D.

Abstract

We have investigated the role of the hematopoietically expressed G16 GTP-binding protein on T cell activation. We constructed transfectants of Jurkat T cells that express a function-deficient mutant of G alpha 16 predicted to prevent activation of this G protein. Upon stimulation with anti-CD3 epsilon antibodies, mutant G alpha 16 transfectants display a profound defect in the production of IL-2 and IL-10, as well as in the expression of CD69. In contrast, the phorbol 12-myristate 13-acetate (PMA)-induced IL-10 production and CD69 expression, and the ionomycin plus PMA-induced IL-2 production are not affected. Consistent with the reduction in cytokine production is the inhibition of early signaling events in the mutant G alpha 16-expressing cells. There are significant reductions in anti-epsilon-induced tyrosine phosphorylation of zeta, epsilon, ZAP-70, and phospholipase C gamma 1, as well as in intracellular Ca2+ mobilization. In accordance with the effects on tyrosine phosphorylation is the reduction of TCR/CD3-mediated Fyn and Lck activities in G alpha 16 mutant cells. Even though the mechanism through which the G alpha 16 mutant mediates inhibition of T cell activation is not known, the data suggest a model where G proteins become activated upon TCR/CD3 engagement and regulate the activation of tyrosine kinases and subsequent downstream signaling events that lead to the activation of cytokine genes.

Publication types

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

MeSH terms

  • Alanine / genetics
  • Amino Acid Substitution / genetics
  • Amino Acid Substitution / immunology
  • Antigens, CD / biosynthesis
  • Antigens, Differentiation, T-Lymphocyte / biosynthesis
  • CD3 Complex / metabolism
  • Calcium / metabolism
  • Enzyme Activation / genetics
  • GTP-Binding Proteins / biosynthesis*
  • GTP-Binding Proteins / genetics*
  • Gene Expression / immunology
  • Glycine / genetics
  • Hematopoietic Stem Cells / enzymology
  • Hematopoietic Stem Cells / immunology
  • Hematopoietic Stem Cells / metabolism*
  • Humans
  • Interleukin-10 / antagonists & inhibitors
  • Interleukin-10 / biosynthesis
  • Interleukin-2 / antagonists & inhibitors
  • Interleukin-2 / biosynthesis
  • Intracellular Fluid / enzymology
  • Intracellular Fluid / metabolism
  • Isoenzymes / metabolism
  • Jurkat Cells
  • Lectins, C-Type
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / antagonists & inhibitors
  • Mutagenesis, Site-Directed*
  • Phospholipase C gamma
  • Phosphorylation
  • Proto-Oncogene Proteins / antagonists & inhibitors
  • Proto-Oncogene Proteins c-fyn
  • Receptor-CD3 Complex, Antigen, T-Cell / physiology*
  • Signal Transduction / genetics
  • Signal Transduction / immunology*
  • Transfection / immunology
  • Type C Phospholipases / metabolism
  • Tyrosine / antagonists & inhibitors
  • Tyrosine / metabolism

Substances

  • Antigens, CD
  • Antigens, Differentiation, T-Lymphocyte
  • CD3 Complex
  • CD69 antigen
  • Interleukin-2
  • Isoenzymes
  • Lectins, C-Type
  • Proto-Oncogene Proteins
  • Receptor-CD3 Complex, Antigen, T-Cell
  • Interleukin-10
  • Tyrosine
  • FYN protein, human
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • Proto-Oncogene Proteins c-fyn
  • Type C Phospholipases
  • Phospholipase C gamma
  • GTP-Binding Proteins
  • Alanine
  • Calcium
  • Glycine