| Abstract: | The expression of early "competence" genes has been examined in murine peritoneal macrophages treated with bacterial lipopolysaccharide (LPS). This set of genes (e.g., c-myc, c-fos, r-fos, JE, and KC) were first described in BALB/c 3T3 cells treated with platelet-derived growth factor. We have previously reported that LPS induces the rapid and transient expression of both c-myc and c-fos in macrophages. In the present report, we present evidence demonstrating that the mRNA for JE and KC are also induced in macrophages after treatment of LPS. The r-fos gene was not detectably induced by LPS under the experimental conditions used in this study. The induction of JE and KC were dependent upon the dose of LPS and exhibited different time courses. mRNA for both KC and JE was induced within 30 min from the initiation of treatment. Although mRNA for JE continued to accumulate for up to 24 hr, mRNA for KC was optimally seen after 60 min and had disappeared by 4 hr. c-fos, JE, and KC mRNA were all inducible by a variety of structurally diverse but functionally similar agents (e.g., heat killed Listeria monocytogenes, maleyl-bovine serum albumin, and fucoidan). Interferon-gamma, a potent but functionally distinct stimulus of macrophage activation, did not effect the expression of JE or KC mRNA. The expression of mRNA for c-fos could be readily induced by treatment of macrophages with phorbol myristate acetate (PMA) alone and that for JE by PMA plus the inophore A23187; mRNA for KC was largely unaffected by these agents. These results suggest that expression of the c-fos and JE genes are regulated by products of polyphosphoinositide hydrolysis. The difference between c-fos or JE and KC raises the possibility that LPS may stimulate at least two independent routes of early gene expression. LPS does not promote macrophage proliferative activity alone, and in fact inhibits the proliferative response to the macrophage growth factor colony-stimulating factor 1. Taken together these findings suggest that the products of these genes may function in the acquisition of competence for highly differentiated functions in addition to that for cell division. |
