The somatic cell-specific low density lipoprotein receptor-related protein of the chicken: close kinship to mammalian low density lipoprotein receptor gene family members

• Published in: The Journal of biological chemistry 1994-01, Vol.269 (1), p.212-219
• Main Authors: NIMPF, J, STIFANI, S, BILOUS, P. T, SCHNEIDER, W. J
• Format: Article
• Language: English
• Subjects: alpha-Macroglobulins - chemistry; alpha-Macroglobulins - genetics; Amino Acid Sequence; Animals; Base Sequence; Biological and medical sciences; Cell receptors; Cell structures and functions; cells; Cells, Cultured; cellule; celulas; chemoreceptors; Chick Embryo; Chickens; chicks; chimiorecepteur; Cloning, Molecular; DNA, Complementary; Female; fibroblaste; fibroblastos; fibroblasts; foie; Fundamental and applied biological sciences. Psychology; gene; genes; higado; Humans; lipoproteinas; lipoproteine; lipoproteins; liver; Low Density Lipoprotein Receptor-Related Protein-1; Male; Miscellaneous; Molecular and cellular biology; Molecular Sequence Data; nucleotide sequence; pollito; pollo; poulet; poussin; proteinas; proteine; proteins; quimioreceptors; Receptors, Immunologic - chemistry; Receptors, Immunologic - genetics; secuencia nucleica; Sequence Homology, Amino Acid; sequence nucleique
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)42336-2

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/alpha2-macroglobulin receptor (LRP/alpha2MR), 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 alpha2-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/alpha2MR expressed in chickens, which do not metabolize chylomicron remnants. This chicken protein is expressed in somatic tissues and is different from a second LRP/alpha2MR exclusively expressed in growing ovarian follicles. The sequence of the somatic cell-specific chicken LRP/alpha2MR, deduced from cloned full-length cDNA, shows 83% overall identity with human LRP/alpha2MR. Important characteristic features of the modular protein are completely conserved; in particular, all cysteine residues align perfectly. The avian LRP/alpha2MR is post-translationally cleaved in the same fashion as its human counterpart, and the resulting 515-kDa extracellular subunit binds Ca2+, alpha2-macroglobulin, and vitellogenin. The results indicate that avian LRP/alpha2MR 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/alpha2MRs have acquired features required for functioning in plasma clearance of certain non-yolk proteins.