Association of B Cell Antigen Receptor with Protein Tyrosine Kinase Lyn

TLDR

Antigen cross‑linking of membrane‑bound immunoglobulins activates B‑cell proliferation and differentiation, and the Src‑like tyrosine kinase Lyn, preferentially expressed in B cells, is implicated in this signal transduction. Lyn physically associates with membrane‑bound IgM, as shown by co‑immunoprecipitation and rapid tyrosine phosphorylation of multiple proteins upon IgM cross‑linking, indicating its role in antigen‑mediated signaling.

Abstract

Antigen is thought to cross-link membrane-bound immunoglobulins (Igs) of B cells, causing proliferation and differentiation or the inhibition of growth. Protein tyrosine kinases are probably involved in signal transduction for cell proliferation and differentiation. The Src-like protein tyrosine kinase Lyn is expressed preferentially in B cells. The Lyn protein and its kinase activity could be coimmunoprecipitated with IgM from detergent lysates. Cross-linking of membrane-bound IgM induced a rapid increase in tyrosine phosphorylation of at least ten distinct proteins of B cells. Thus, Lyn is physically associated with membrane-bound IgM, and is suggested to participate in antigen-mediated signal transduction.