MIP-1alpha induces differential MAP kinase activation and IkappaB gene expression in human B lymphocytes.

The chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) stimulates migration of B cells and affects B cell immunoglobulin production. However, the molecular mechanisms by which MIP-1alpha modulates these biologic effects have not been completely defined. Previously, we demonstrated that treatment of B cells with MIP-1alpha induced the transcription factor, nuclear factor (NF)-kappaB, to bind to DNA, concomitant with the degradation of IkappaBalpha, a cytoplasmic inhibitor of NF-kappaB activation. Here, we report that MIP-1alpha treatment of tonsil B cells induced IkappaB gene expression that was dependent on MIP-1alpha-mediated activation of a pathway(s) involving NF-kappaB and phosphatidylinositol-3 kinase (PI3K). The NF-kappaB pathway is understood to be controlled in an autoregulatory fashion, so expression of IkappaB is thought to provide a means by which B cells modulate this pathway after stimulation with MIP-1alpha. Although the idea of NF-kappaB autoregulation is not novel, this is the first report to suggest the regulation of B cell gene expression by MIP-1alpha. In addition, we observed the activation of Jun N-terminal kinase (JNK) and p38 mitogenic-activated protein kinase (MAPK), but not extracellular signal-related kinase (ERK) in response to MIP-1alpha. Although p38 and NF-kappaB activity were both necessary for B cell migration, IkappaB gene expression was not affected by p38 inhibition, suggesting that p38 is involved in a separate MIP-1alpha-mediated signal transduction pathway.