Glycosyl-phosphatidylinositol-anchored or integral membrane forms of CD14 mediate identical cellular responses to endotoxin.

Open Access
Publisher Website
Google Scholar
Abstract
Endotoxin stimulates leukocytes to release cytokines that initiate septic shock in humans and animals. CD14, a glycosyl-phosphatidylinositol-anchored membrane glycoprotein, is an endotoxin receptor on leukocytes, and endotoxin binding to CD14 induces cytokine production. Here we show that glycosyl-phosphatidylinositol-anchored or integral membrane CD14 mediates identical cellular responses to endotoxin, including NF-kappaB activation and protein tyrosine phosphorylation. We also show that an anti-CD14 monoclonal antibody that does not block endotoxin binding to CD14 nonetheless inhibits cell activation by endotoxin. These findings suggest that binding of endotoxin to cell-surface CD14 is followed by subsequent interactions of the endotoxin-CD14 complex with additional membrane component(s) that enable transmembrane signaling. This function of CD14 may be prototypic for other members of the glycosyl-phosphatidylinositol-anchored family of proteins that do not play a primary role in signal transduction but rather are the principal ligand-binding units of membrane-bound receptor complexes.