title: Isolation of a human endothelial cell C1q receptor (C1qR).
abstract: C1q binding to endothelial cells has been described previously, but the putative cell surface receptor(s) has not been identified. In the present study, modifications of a reported purification of lymphocyte C1q receptor (C1qR) were used to isolate C1q binding sites from human umbilical vein endothelial cells. Cells were harvested, without protease treatment, at passage 10-17 and lysed with 1% Triton X-100. The lysate was fractionated on Fast-performance liquid chromatography (FPLC) Mono-Q using a linear NaCl gradient, followed by high-performance liquid chromatography (HPLC) ion exchange (TSKgel DEAE-NPR). A major protein was eluted that had the same mobility on sodium dodecyl sulfate-polyacrylamide gels and the same NH2-terminal sequence as lymphocyte C1qR. This protein was expressed on the surface, as judged by surface radioiodination, bound to C1q-coated surfaces, and was recognized by polyclonal antilymphocyte C1qR antibodies. Thus, endothelial cells express a C1q receptor that appears identical to lymphocyte C1qR. The data further support the hypothesis that cell surface C1qRs identified on a variety of somatic and cultured cells are either identical or constitute a family of closely related molecules.
authors.affiliation: MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, United Kingdom.
authors.forename: E I
authors.initials: EI
authors.lastname: Peerschke
authors.forename: R
authors.initials: R
authors.lastname: Malhotra
authors.forename: B
authors.initials: B
authors.lastname: Ghebrehiwet
authors.forename: K B
authors.initials: KB
authors.lastname: Reid
authors.forename: A C
authors.initials: AC
authors.lastname: Willis
authors.forename: R B
authors.initials: RB
authors.lastname: Sim
mesh_terms: D000595:Amino Acid Sequence; D001345:Autoradiography; D002352:Carrier Proteins; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004730:Endothelium, Vascular / Q000276:immunology*; D006801:Humans; D018960:Hyaluronan Receptors; D007457:Iodine Radioisotopes; D007700:Kinetics; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011951:Receptors, Complement / Q000302:isolation & purification* / Q000378:metabolism; D014471:Umbilical Veins
chemical_list: C087299:C1QBP protein, human; D002352:Carrier Proteins; D018960:Hyaluronan Receptors; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D011951:Receptors, Complement; C032402:complement 1q receptor