IDENTIFICATION OF A NOVEL 85-KDA LIPOPROTEIN-LIPASE BINDING-PROTEIN ON HUMAN AORTIC ENDOTHELIAL-CELL SURFACE

Lipoprotein lipase (LPL), bound to the luminal surface of vascular end othelium catalyzes lipoprotein triglyceride hydrolysis. Studies were p erformed to identify human aortic endothelial (HAEC) cell-surface prot eins having high affinity for LPL. LPL-sepharose affinity chromatograp hy of [S-35]O-4 labeled HAEC proteins identified a 220-kDa proteoglyca n. Ligand blotting of HAEC plasma membrane proteins with LPL revealed two specific binding proteins of MW 116 kDa and 85 kDa, respectively, which were not released from the cell-surface by heparin treatment. Si nce the 220-kDa and 116-kDa proteins have been reported previously in bovine endothelial cells, we focussed on the 85-kDa protein. The 85-kD a protein was not labelled by incubation of the cells with [S-35]O-4, suggesting that it is not a sulfated proteoglycan. Treatment of HAEC w ith tunicamycin markedly decreased detection of the 85-kDa protein, su ggesting that it is likely a glycoprotein synthesized by HAEC. We conc lude that HAEC cell surface has three specific LPL binding proteins, a 220-kDa proteoglycan, a 116-kDa protein and a novel 85-kDa protein. ( C) 1995 Acidemic Press, Inc.