title: Characterization of residues in the cytoplasmic domain of the LDL receptor required for exit from the endoplasmic reticulum.
abstract: Newly synthesized low density lipoprotein receptors (LDLRs) exit the endoplasmic reticulum (ER) as the first step in the secretory pathway. In this study we have generated truncating deletions and substitutions within the 50 amino acid cytoplasmic domain of the LDLR in order to identify residues required for the exit from the ER. Western blot analysis was used to determine the relative amounts of the 120 kDa precursor form of the LDLR located in the ER and the 160 kDa mature form that has exited the ER. These studies have shown that the exit of an LDLR lacking the cytoplasmic domain, is markedly reduced. Moreover, the longer the cytoplasmic domain, the more efficient is the exit from the ER. At least 30 residues were required for the LDLR to efficiently exit the ER. Mutations in the two di-acidic motifs ExE(814) and/or ExD(837) had only a small effect on the exit from the ER. The requirement for a certain length of the cytoplasmic domain for efficient exit from the ER, could reflect the distance needed to interact with the COPII complex of the ER membrane or the requirement for the LDLR to undergo dimerization.
authors.affiliation: Unit for Cardiac and Cardiovascular Genetics, Department of Medical Genetics, Oslo University Hospital Rikshospitalet, NO-0027 Oslo, Norway.
authors.forename: Thea Bismo
authors.initials: TB
authors.lastname: Strøm
authors.forename: Kristian
authors.initials: K
authors.lastname: Tveten
authors.forename: Øystein L
authors.initials: ØL
authors.lastname: Holla
authors.forename: Jamie
authors.initials: J
authors.lastname: Cameron
authors.forename: Knut Erik
authors.initials: KE
authors.lastname: Berge
authors.forename: Trond P
authors.initials: TP
authors.lastname: Leren
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011973:Receptors, LDL / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D011973:Receptors, LDL