Serine phosphorylation of a 67-kDa protein in human T lymphocytes represents an accessory receptor-mediated signaling event.
Phosphorylation on serine residues of a 67-kDa cytoplasmic protein (p67) occurs as an early signaling event after stimulation of resting human T cells via CD2 but not via TCR/CD3. Phosphorylation of p67 is, however, not restricted to CD2 stimulation because it can also be induced by costimulation through CD4 and CD8 coreceptors when approximated to the TCR-CD3 complex, suggesting a common signaling mechanism for these accessory receptors of the Ig superfamily. Because late functional responses of T cell activation like IL-2 production and DNA synthesis correlate with phosphorylation of p67, this intracellular event may represent an accessory receptor-mediated costimulatory second signal for human T cell activation. The biochemical characteristics (m.w. and isoelectric point) of p67 are identical with those of the actin binding protein L-plastin (Fimbrin), a cytoplasmic protein that contains two Ca2+ binding sites and a calmodulin binding domain. Moreover, p67 reacts specifically with an L-Plastin (Fimbrin) antiserum.
Henning
S W
SW
Applied Immunology, German Cancer Research Center, Heidelberg.
Meuer
S C
SC
Samstag
Y
Y
D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis / Q000502:physiology; D015153:Blotting, Western; D018801:CD2 Antigens; D018106:CD28 Antigens / Q000502:physiology; D017252:CD3 Complex / Q000032:analysis / Q000502:physiology; D006801:Humans; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D011971:Receptors, Immunologic / Q000032:analysis / Q000502:physiology*; D012694:Serine / Q000378:metabolism*; D013601:T-Lymphocytes / Q000502:physiology*
D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D018106:CD28 Antigens; D017252:CD3 Complex; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D010750:Phosphoproteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011971:Receptors, Immunologic; C026742:plastin; D012694:Serine