Interferon γ-dependent Induction of Human Intercellular Adhesion Molecule-1 Gene Expression Involves Activation of a Distinct STAT Protein Complex

Abstract

In response to interferon ␥ (IFN␥), intercellular adhesion molecule-1 (ICAM-1) is expressed on human keratinocytes, a cell type that is critically involved in cutaneous inflammation. An ICAM-1 5 regulatory region palindromic response element, pI␥RE, has been shown to confer IFN␥-dependent transcription enhancement. By electrophoretic mobility shift assays (EMSA), pI␥RE forms a distinct complex with proteins from IFN␥-treated human keratinocytes, termed ␥ response factor (GRF). Binding of GRF is tyrosine phosphorylation-dependent, and mutations of pI␥RE that disrupt the palindromic sequence or alter its spatial relationship abrogate GRF binding. Supershift EMSAs using antibodies to characterized STAT proteins suggest that GRF contains a Stat1␣-like protein; however, non-ICAM-1 IFN␥-responsive elements (REs) known to bind Stat1␣ homodimers fail to compete for GRF binding in EMSA, and pI␥RE does not cross-compete with these REs that complex with homodimeric stat1␣. The pI␥RE⅐GRF complex also displays a distinctly different electrophoretic mobility compared to that of IFN␥REs complexed to homodimeric Stat1␣. These findings indicate that a distinct complex containing a Stat1␣-like protein mediates IFN␥-induced ICAM-1 gene transcription and identifies a subset of IFN␥-responsive genes that appear to be regulated by this complex.

Differential Regulation of Chemokine Production in Human Peritoneal Mesothelial Cells: IFN-γ Controls Neutrophil Migration Across the Mesothelium In Vitro and In Vivo

“…Previous reports indicate IFN-␥ up-regulates ICAM-1 expression on many cell types, including mesothelium (4,47,48). We have shown previously that ICAM-1 was required for both basal and IL-1␤-induced transmesothelial PMN migration (7).…”

Regulation of Cyclooxygenase-2 by Interferon γ and Transforming Growth Factor α in Normal Human Epidermal Keratinocytes and Squamous Carcinoma Cells

“…IFN-␥ has also been reported to affect growth and differentiation in cultured epidermal keratinocytes (14,15,(22)(23)(24)(25) and has been implicated in several inflammatory skin diseases, such as allergic contact dermatitis and psoriasis (14, 26 -29). Sites of inflammation contain elevated levels of IFN-␥ and intercellular adhesion molecule-1 (ICAM-1), which plays a pivotal role in the adhesion and migration of leukocytes at sites of inflammation, and ICAM-1 is dramatically induced by IFN-␥ in epidermal keratinocytes (26).…”

Transcriptional regulation of the intercellular adhesion molecule-1 gene by proinflammatory cytokines in human astrocytes

“…These results suggest that a STAT-1␣-containing complex is activated upon IFN-␥ stimulation in primary human astrocytes, and transactivates ICAM-1 expression by binding to the proximal GAS sequence. In human keratinocytes, IFN-␥ stimulation induces a protein complex distinct from the STAT-1␣ homodimer that binds to the ICAM-1 GAS sequence (Naik et al, 1997). To characterize further the STAT-1␣ complex from astrocytes binding to this element, we attempted to compete away the STAT-1␣ containing complex using several GAS sequences from different genes known to bind to the STAT-1␣ homodimer ( Fig.…”