Protein kinase C-alpha modulates lipopolysaccharide-induced functions in amurine macrophage cell line

Lipopolysaccharide (LPS), a potent modulator of macrophage functional activ ity, binds to CD14 and triggers the activation of several protein kinases, leading to the secretion of variety of immunomodulatory molecules such as n itric oxide and proinflammatory cytokines. In this study, we have examined the role of the alpha isoenzyme of protein kinase C (PKC) in the regulation of LPS-initiated signal transduction in macrophages. To this end, we have stably overexpressed a dominant-negative (DN) version of PKC-alpha (DN PKC- alpha) in the murine macrophage cell line RAW 264.7. Clones overexpressing DN PKC-alpha were indistinguishable from the parental line with respect to morphology and growth characteristics. At the functional level, DN PKC-alph a overexpression strongly inhibited LPS-induced interleukin-la mRNA accumul ation, and to a lesser extent inducible nitric oxide synthase and tumor nec rosis factor-alpha expression. DN-PKC-alpha overexpression did not cause a general unresponsiveness to LPS, as secretion of the matrix metalloproteina se-9 was up-regulated in our DN PKC-alpha-overexpressing clones. Moreover, LPS-induced phosphorylation and degradation of I kappa B alpha, NF-kappa B activation, as well as p38 mitogen-activated protein kinase and Jun N-termi nal kinase phosphorylation, were not affected by DN PKC-alpha overexpressio n. Collectively, these data provide evidence that PKC-alpha regulates selec tive LPS-induced macrophage functions involved in host defense and inflamma tion.