A ROLE FOR CALCITONIN-GENE-RELATED PEPTIDE (CGRP) IN THE REGULATION OF EARLY B-LYMPHOCYTE DIFFERENTIATION

In previous studies we identified high affinity adenylyl cyclase linked receptors for calcitonin gene related peptide (CORP) on rat T and B cells, on lymphocyte cell lines including the mouse pre-B cell line 70Z/3, and on cells in mouse bone marrow. The effect of CGRP on early B cell differentiation has been examined using the 70Z/3 cell line. CGRP inhibits the lipopolysaccharide (LPS) induction of surface immunoglobulin (sig) protein expression in 70Z/3 cells, an effect that is associated with a decrease in the steady-state levels of Ig heavy (mu) and light (kappa) chain mRNA. In this report, experiments are described that provide further information on the mechanism by which CORP inhibits sig expression. The kinetics of CORP inhibition of LPS-induced sig expression was examined in 70Z/3 cells. An optimal window for the inhibitory effect of CORP on sig induction occurs at least 24 h after the cells are treated with LPS. To determine whether the inhibitory effects of CGRP on sig expression are mediated by an inhibition of NK kappa-B translocation to the nucleus, electrophoretic mobility shift assays were performed using nuclear proteins from 70Z/3 cells. There was no difference in NF kappa-B binding activity in cells that had been treated with LPS or LPS + CORP, suggesting that the inhibitory effect of CORP is not mediated by an inhibition of NF kappa-B activity. These studies provide further evidence that CORP plays an inhibitory role in early B cell differentiation. Finally, a model is proposed that describes an integrated role for CORP in the homeostatic regulation of early B cell differentiation.