TRANSCRIPTIONAL REGULATION OF INTERCELLULAR-ADHESION MOLECULE-1 - PMA-INDUCTION IS MEDIATED BY NF-KAPPA-B

The surface glycoprotein intercellular adhesion molecule-1 (ICAM-1) mediates important immunologic cell interactions during cutaneous inflammatory processes by binding to the leukocyte integrin lymphocyte function-associated antigen-1. The expression of ICAM-1 is induced in epidermal keratinocytes by certain pro-inflammatory stimuli, and this modulation is transcriptionally regulated. To identify the molecular mechanisms involved in the regulation of ICAM-1 gene expression, we have previously cloned the transcriptional regulatory region of the human ICAM-1-gene and have characterized a functional promoter. Here we have used the phorbol ester phorbol-12-myristate-13-acetate (PMA) to further evaluate the transcriptional mechanisms of ICAM-1 gene induction in A431 cells. Exposure to PMA induced ICAM-1 both at the mRNA and cell surface level. Promoter activity and PMA-enhanced effects were assessed by transiently transfecting A431 cells with chloramphenicol acetyl transferase reporter gene constructs containing a series of sequential ICAM-1 5' deletions. Constructs containing ICAM-1 5' fragments from -1162/+1 (relative to the transcription start site) to -277/+1 displayed a threefold increase in promoter activity when cells were stimulated with PMA. Inducibility dropped below 1.5-fold in chloramphenicol acetyl transferase construct -182/+1. Using electrophoretic mobility shift assays, a PMA-inducible binding site was identified for an NF kappa B-like complex within positions -186/-177. A -199/-170 fragment containing this NF kappa B-like element conferred PIMA responsiveness when cloned into a thymidine kinase-driven chloramphenicol acetyl transferase vector, indicating that the region containing this NF kappa B-like element is not only necessary but also sufficient for PMA induction of ICAM-1.