FIG. 4.
Expression and tyrosine phosphorylation of LMP2A, Lyn, and Syk after BCR cross-linking in LMP2A PY1PY2 LCLs. BJAB cells and LCLs (107 cells) were untreated (−) or treated with anti-human Ig antibodies for the indicated times (1 or 5 min), lysed in Triton X-100 lysis buffer, and immunoprecipitated (IP) with anti-LMP2A (A), anti-Lyn (B), or anti-Syk (C) antibody. Precipitated proteins were separated on sodium dodecyl sulfate–7.5% polyacrylamide gel electrophoresis gels and transferred to Immobilon membranes. To determine the amount of each protein in the immunoprecipitation (top), membranes were immunoblotted with anti-LMP2A (A), anti-Lyn (B), or anti-Syk (C) antibody. To determine the level of tyrosine phosphorylation (bottom), membranes were immunoblotted with horseradish peroxidase-conjugated anti-phosphotyrosine antibody (RC20). Relevant proteins are indicated with arrows, and molecular mass standards are shown (in kilodaltons).