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pubmed:abstractText |
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.
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