Selective binding of shc-SH2 domain to tyrosine-phosphorylated zeta but not gamma-chain upon CD16 ligation on human NK cells.
Fc gamma RIII (CD16) is a hetero-oligomeric receptor composed of a ligand-binding alpha subunit associated with homo- or heterodimers of the TCR zeta- and Fc epsilon RI gamma-chains. We have previously demonstrated that CD16 ligation promotes complex formation between tyrosine-phosphorylated shc and Grb2, leading to activation of ras signaling pathway in human NK cells. Here we report that CD16 engagement induces rapid shc association with the tyrosine-phosphorylated receptor complex in human NK cells. In vitro binding studies demonstrate that this interaction is mediated by the shc-SH2 domain, and immunodepletion experiments indicate that the zeta- but not the gamma-chain has the capability to mediate this association. Jurkat cell clones expressing CD16-zeta or -gamma homodimers have been used to gain more information about the mechanism of shc/CD16 association. Our data show that, while engagement of both receptors induces tyrosine phosphorylation of shc and Grb2 recruitment, shc-SH2/receptor complex association is evident only in CD16-zeta but not in CD16-gamma transfectants. Overall, our data demonstrate that the adaptor protein shc can be recruited to the activated CD16 complex by interaction with tyrosine-phosphorylated zeta-chain in a SH2-dependent manner. These results also provide further support to the notion that zeta- and gamma-chains might couple to different biochemical pathways.
Galandrini
R
R
Department of Experimental Medicine and Pathology, University La Sapienza, Rome, Italy.
Palmieri
G
G
Paolini
R
R
Piccoli
M
M
Frati
L
L
Santoni
A
A
D002478:Cells, Cultured; D006801:Humans; D019169:Jurkat Cells; D007694:Killer Cells, Natural / Q000378:metabolism*; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000378:metabolism*; D017452:Receptors, IgG / Q000378:metabolism*; D014162:Transfection / Q000276:immunology; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains / Q000276:immunology*
D008024:Ligands; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; D016692:Receptors, Antigen, T-Cell, gamma-delta; D017452:Receptors, IgG; C054979:antigen T cell receptor, zeta chain; D014443:Tyrosine