Mutation of tyrosine 145 of lymphocyte cytosolic protein 2 protects mice from anaphylaxis and arthritis.

BACKGROUND

Lymphocyte cytosolic protein 2, also known as Src homology 2 domain-containing leukocyte phosphoprotein of 76 kilodaltons (SLP-76), is an essential adaptor molecule in myeloid cells, where it regulates FcepsilonRI-induced mast cell (MC) and FcgammaR- and integrin-induced neutrophil (polymorphonuclear leukocyte [PMN]) functions. SLP-76 contains 3 N-terminal tyrosines at residues 112, 128, and 145 that together are critical for its function.

OBJECTIVE

We sought to explore the relative importance of tyrosines 112, 128, and 145 of SLP-76 during MC and PMN activation.

METHODS

We examined in vitro MC and PMN functions using cells isolated from knock-in mice harboring phenylalanine substitution mutations at tyrosines 112 and 128 (Y112/128F) or 145 (Y145F). We also examined the effects of these mutations on in vivo MC and PMN activation using models of anaphylaxis, dermal inflammation, and serum-induced arthritis.

RESULTS

Mutations at Y112/Y128 and Y145 both interfered with SLP-76 activity; however, Y145F had a greater effect than Y112/128F on most in vitro FcR-induced functions. In vitro functional defects were recapitulated in vivo, where mice expressing Y145F exhibited greater attenuation of MC-dependent passive systemic anaphylaxis and PMN-mediated inflammatory responses. Notably, the Y145F mutation completely protected mice against development of joint-specific inflammation in the MC and PMN-dependent K/B x N model of arthritis.

CONCLUSION

Our data indicate that Y145 is the most critical tyrosine supporting SLP-76 function in myeloid cells. Future efforts to dissect how Y145 mediates SLP-76-dependent signaling in MCs and PMNs will increase our understanding of these lineages and provide insights into the treatment of allergy and inflammation.