title: Two factor H-related proteins from the mouse: expression analysis and functional characterization.
abstract: Complement factor H-related (FHR) proteins display structural and functional similarities to each other and to the complement regulator factor H (FH). FHRs have been identified in various species, including human, rat, and the fish barred sand bass. As mice provide a useful model system to study the physiological role of FHRs in vivo, we aimed at characterizing murine FHR proteins. Two putative FHRs of approximately 100 and 38 kDa were detected in mouse plasma using FH-specific antiserum. In a liver cDNA library, three murine FHR-encoding transcripts were identified. Two clones code for related FHR proteins termed FHR-C and FHR-C_v1, which in secreted form are composed of 14 and 13 short consensus repeat (SCR) domains, homologous to SCRs 6-17 and 19-20 of FH. The third transcript, FHR-B, is derived from a separate gene and codes for a secreted protein composed of five SCR domains. FHR-B displays homology to SCRs 5-7 and 19-20 of FH. Expression of FHR-B in various tissues was analyzed by real-time polymerase chain reaction and was identified at high levels in liver, kidney and heart. In liver, FHR-B transcript level was even higher than that of FH. In addition, FHR-B was expressed as a recombinant 37-kDa protein, and this recombinant FHR-B interacted with the ligands heparin and human C3b. Using mouse plasma, the native presumptive FHR proteins were also analyzed in binding assays. In summary, we identify two FHR proteins in mice and for the first time characterize a murine FHR as a heparin- and C3b-binding protein.
authors.affiliation: Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute, Jena, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hellwage
authors.forename: Florian
authors.initials: F
authors.lastname: Eberle
authors.forename: Tanja
authors.initials: T
authors.lastname: Babuke
authors.forename: Harald
authors.initials: H
authors.lastname: Seeberger
authors.forename: Heiko
authors.initials: H
authors.lastname: Richter
authors.forename: Anja
authors.initials: A
authors.lastname: Kunert
authors.forename: Albert
authors.initials: A
authors.lastname: Härtl
authors.forename: Peter F
authors.initials: PF
authors.lastname: Zipfel
authors.forename: T Sakari
authors.initials: TS
authors.lastname: Jokiranta
authors.forename: Mihály
authors.initials: M
authors.lastname: Józsi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017242:Complement Factor H / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000302:isolation & purification; D008024:Ligands; D008099:Liver / Q000737:chemistry; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D008024:Ligands; D011994:Recombinant Proteins; D017242:Complement Factor H