Characterization of a hyaluronan receptor on rat sinusoidal liver endothelial cells and its functional relationship to scavenger receptors

Hyaluronan is a widely distributed extracellular component of connective ti ssue with several mechanical and cell biological functions. The serum level of hyaluronan is elevated in rheumatic and liver diseases and in certain m alignancies. The major route of hyaluronan clearance from the blood is via the liver, taken up predominantly by sinusoidal liver endothelial cells. We have purified a novel hyaluronan binding protein from liver that also has an affinity for the N-terminal propeptide of type I procollagen, a physiolo gical scavenger receptor Ligand. A polyclonal antibody raised against the p rotein was found to inhibit the binding and degradation of hyaluronan as we ll as two scavenger receptor ligands by cultured sinusoidal liver endotheli al cells, Immunostaining of nonpermeabilized liver cells and liver sections showed chat the antibody specifically stains the surface of sinusoidal liv er endothelial cells. After pretreatment with monensin to block the recircu lation of endocytic receptors, the immunostaining was specifically associat ed with early endosomes of these cells, Thus, this rat sinusoidal liver end othelial cell hyaluronan receptor shares functional properties with the sca venger receptor family, a group of proteins shown to play a key role in the uptake of atherogenic lipids and other waste products from the tissues.