Identification and characterization of three cDNAs that encode putative novel hyaluronan-binding proteins, including an endothelial cell-specific hyaluronan receptor.

The glycosaminoglycan hyaluronan (HA) and HA-binding proteins (HABPs) serve important structural and regulatory functions during development and in maintaining adult tissue homeostasis. Here we have identified and partially characterized the sequence and expression pattern of three putative novel HABPs. DNA sequence analysis revealed that two of the novel HABPs, WF-HABP and BM-HABP, form a unique HA-binding subfamily, whereas the third protein, OE-HABP, is more closely related to the LINK subfamily of HABPs. Northern blotting experiments revealed that the expression of BM-HABP was highly restricted, with substantial expression detected only in human fetal liver. In contrast, WF-HABP and OE-HABP mRNAs were detected in a number of tissues, with particularly prominent expression in highly vascularized tissues such as the heart, placenta, and lung. Additional studies showed that OE-HABP was expressed by cultured human endothelial cells, smooth muscle cells, and differentiated monocytes. However, only endothelial cells expressed WF-HABP mRNA, and its expression was regulated by growth state, being most prominent in quiescent endothelial cells. We further characterized the expression of WF-HABP in vivo and found that its expression colocalized with CD31-positive cells and was prominently expressed in microvessels in the human aorta and in atherectomy samples. Our data suggest that WF-HABP is an endothelial cell-specific HA receptor and that it may serve a unique function in these cells. The WF-HABP gene was localized to chromosome 3p21.31 and the OE-HABP gene to 15q25.2-25.3.