DIFFERENTIAL REGULATION OF VASCULAR CELL-ADHESION MOLECULE-1 GENE-EXPRESSION BY SPECIFIC NF-KAPPA-B SUBUNITS IN ENDOTHELIAL AND EPITHELIAL-CELLS

Vascular cell adhesion molecule 1 (VCAM-1) is expressed in both endothelial and epithelial cell types, where it contributes to lymphocyte migration to sites of inflammation. Its expression is regulated by cytokines, in part through two kappaB-like regulatory elements. Because NF-kappaB can be composed of multiple alternative subunits with differential effects on gene expression, the role of different specific NF-kappaB family members subunits in VCAM-1 regulation is unknown. In this report, we define the contribution of different NF-kappaB family members to VCAM-1 gene regulation. We show that both kappaB sites in the VCAM-1 enhancer are required to optimally stimulate gene expression, but the enhancer is differentially regulated by specific combinations of NF-kappaB subunits. At low concentrations, RelA(p65) acted in concert with the approximately 50-kDa product of p105 NF-kappaB, NF-kappaB1(p50), to stimulate transcription, and at high concentrations, RelA(p65) alone stimulated the VCAM-1 promoter. In contrast, NF-kappaB2 inhibited functional activation of the VCAM reporter by p65. Consistent with this finding, an additional binding complex was detected by using recombinant NF-kappaB2(p49)/RelA(p65) with radiolabeled VCAM kappaB site probes. Interestingly, the human immunodeficiency virus enhancer responded differently to stimulation by NF-kappaB subunits, with optimal response to p49(100)/p65. Analysis of NF-kappaB mRNA in human umbilical vein endothelial cells revealed that nfkb1, nfkb2, and relA NF-kappaB but not c-rel were induced by tumor necrosis factor alpha and lipopolysaccharide, which also induce VCAM-1. These data suggest that specific subunits of NF-kappaB regulate VCAM-1 and differentially activate other genes in these cells.