REGULATION OF INTERLEUKIN-1 SIGNALING THROUGH INTEGRIN BINDING AND ACTIN REORGANIZATION - DISPARATE EFFECTS ON NF-KAPPA-B AND STRESS KINASEPATHWAYS

Interleukin 1 (IL-l)-mediated gene regulation is dependent on cell-mat rix interactions. Both IL-l-activated pathways, nuclear factor kappa B (NF-kappa B) and the stress-activated protein kinase (SAPK), can be r egulated by cell adhesion and changes in the cytoskeleton, suggesting that cell-matrix effects on IL-1 responses are initiated in part thoug h effects on signal transduction. Here we show that IL-l-induced trans ient alterations in cell shape and in the cytoskeleton in fibronectin attached cells are correlated with effects on peak activity of NF-kapp a B and SAPK. Cells on fibronectin showed a 1.5-2-fold enhancement in IL-l-induced NF-kappa B activity compared with levels in cells on poly (L-lysine) or bare tissue culture plates. The effect was increased wit h increasing concentrations of fibronectin and was most prominent at l ower concentrations of IL-1. In contrast, fibronectin attachment cause d an approx. 50% decrease in the IL-I activation of SAPK, eliminating the peak activity after 15 min of stimulation with IL-1. IL-1-induced NF-kappa B activity showed a successive, substratum-independent increa se during 4h of attachment and spreading, whereas the inhibitory effec t of fibronectin on the SAPK pathway was induced at the initial stages of attachment. Further, the addition of a peptide containing the moti f RGD resulted in a 40%, decrease in NF-kappa B activity in cells on f ibronectin, largely accounted for by an effect on the p50/p65 heterodi mer. Similarly, blocking of integrin aggregation by RGD-containing pep tide resulted in a total abrogation of the fibronectin effect on IL-1- induced SAPK activity, The results demonstrate disparate effects of ce ll adhesion on the activation by IL-I of the NF-kappa B and SAPK pathw ays. Thus fibronectin attachment causes an upregulation of NF-kappa B activity in the presence of IL-1, whereas in contrast it results in a pronounced decrease in IL-1-induced SAPK activity.