Phosphorylation of p42/44 MAP kinase is required for rF1-induced activation of murine peritoneal macrophages

The Fraction 1 (F1) antigen of Yersinia pestis is known to induce thymocyte proliferation. It serves as a major protective antigen against challenge of Y. pestis. Recently, we reported rF1-induced activation of macrophages. Current investigation elucidates the role of p42/44 mitogen-activated protein kinases (MAPK)-mediated signal transduction in murine peritoneal macrophages on stimulation with rF1 (10 μg/ml) in vitro. The p42/44 MAPK activation was determined by studying the expression of the phosphorylated p42/44 MAPK in rF1-treated macrophages. PD98059, a specific inhibitor of MAPK kinase (MEK) inhibited the p42/44 MAPK phosphorylation, indicating the specificity of the above response. Furthermore, the rF1-induced phosphorylation of p42/44 MAPK is found to blocked by upstream protein kinase C inhibitor H7, tyrosine kinase inhibitor genistein and phosphoinositol-3-kinase (PI3-K) inhibitor wortmannin. Additionally, phosphorylation of JNK and activation of the transcription factor, c-jun and c-fos was also observed in response to rF1 treatment. The rF1-induced activation of p42/44 MAPK was correlated to the functional activation of macrophages by demonstrating the inhibition of actin rearrangement, IL-1, TNF-α and NO production caused by PD98059 in the rF1-treated macrophages.