title: The somatic cell-specific low density lipoprotein receptor-related protein of the chicken. Close kinship to mammalian low density lipoprotein receptor gene family members.
abstract: Recently, the family of mammalian genes homologous to that for the low density lipoprotein (LDL) receptor has grown. One of the new family members, termed LDL receptor-related protein/alpha 2-macroglobulin receptor (LRP/alpha 2MR), is one of the largest cell surface proteins characterized to date. Its functions have been hypothesized to include the plasma clearance of chylomicron remnants and activated alpha 2-macroglobulin, as well as the local metabolism of complexes between plasminogen activators and their endogenous inhibitors. Here we describe the molecular characterization of an LRP/alpha 2MR expressed in chickens, which do not metabolize chylomicron remnants. This chicken protein is expressed in somatic tissues and is different from a second LRP/alpha 2MR exclusively expressed in growing ovarian follicles. The sequence of the somatic cell-specific chicken LRP/alpha 2MR, deduced from cloned full-length cDNA, shows 83% overall identity with human LRP/alpha 2MR. Important characteristic features of the modular protein are completely conserved; in particular, all cysteine residues align perfectly. The avian LRP/alpha 2MR is post-translationally cleaved in the same fashion as its human counterpart, and the resulting 515-kDa extracellular subunit binds Ca2+, alpha 2-macroglobulin, and vitellogenin. The results indicate that avian LRP/alpha 2MR genes have emerged from an ancestor designed to ensure a pivotal event in the reproduction of oviparous species, i.e. vitellogenesis, and that mammalian LRP/alpha 2MRs have acquired features required for functioning in plasma clearance of certain non-yolk proteins.
authors.affiliation: Department of Molecular Genetics, Biocenter, Vienna, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Nimpf
authors.forename: S
authors.initials: S
authors.lastname: Stifani
authors.forename: P T
authors.initials: PT
authors.lastname: Bilous
authors.forename: W J
authors.initials: WJ
authors.lastname: Schneider
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005260:Female; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008297:Male; D008969:Molecular Sequence Data; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D000511:alpha-Macroglobulins / Q000737:chemistry / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins