Biochimica et Biophysica A cta, 1009(1989) 229-236 Elsevier 229 BBAEXP 92006 Structure of the low-density lipoprotein receptor-related protein (LRP) promoter Heike Ktitt, Joachim Herz * and Keith K. Stanley European Molecular Biology Laboratory, Heidelberg (F.R.G.) (Received4 July 1989) Key words: Lowdensitylipoprotein;Lipoprotein receptor; Promoter;Apolipoprotein E receptor; LRP promoter The low-density Hpoprotein receptor-related protein (LRP) is a 45,~-amin~acid membrane protein which c|ose|y resembles the |,DL receptor in its arrangement of cysteine-rich motifs. Binding studies have suggested that one function of the molecule is as a receptor for Hgands containing apo|ipoprotein E. We present here the sequence and stn|cture of the promoter region of the LRP. These data show that the LRP contains no sterol regulatory e|ement, and is not down-regulated by sterois like the LDL receptor. This [ends further support to the identity of the LRP as a chyiomicron remnant receptor. Introduction Lipoprotein receptors are important for controlling the concentration of plasma lipoprotein particles. De- fects in the structure or regulation of the genes encoding these proteins can account for familial iipoprotein dis- orders leading to atherosclerosis. Studies on the low- density lipoprotein (LDL) receptor sequence in patients having familial hypercholesteroleemia have led to the definition of four classes of mutant with impaired LDL uptake [1]. These mutations affect the synthesis, intra- cellular transport, LDL binding and clustering into coated pits of the receptor molecule. Plasma LDL levels are also affected by the gene regulation of the LDL receptor, high intracellular cholesterol giving rise to a down-regulation of receptor transcription [2]. The molecular mechanism for this regulatior~ has been ascribed to a sterol regulatory element which is found in the promoter region of the LDL receptor gene [2]. Similar elements have also been found in the genes for * Present address: Department of MolecularGenetics and Internal Medicine, Universityof Texas Health ScienceCenter, 5823 Harry Hines Boulevard,Dallas,TX 75235, U.S.A. Abbreviations: LRP, low-density lipoprotein receptor-like protein; HMG, hydroxymethylglutaryl; CAT, chloroamphenicolacetyitrans- ferase (EC 2.3.1.28); PBS,phosphate-buffered saline; PMSF, phenyl- methylsulphonylfluoride; MEM, minimum essential medium; DT~7, dithiothreitol; SRE, sterol regulatory element. Correspondence(present address): K.K. Stanley,The Heart Research Institute, 145-147 Missenden Road, Camperdown,NSW 2050, Syd- ney, Australia. 0167-4781/89/$03.50 © 1989 ElsevierSciencePublishersB.V.(Biomedical HMG-CoA reductase [3] and HMG-CoA synthase pro- moters [4]. This enables a co-ordinated regulation of the genes controlling cholesterol homeostasis. Recently, a cell surface receptor has been described with a predicted polypeptide molecular mass of 503 kDa and a sequence highly related to the LDL receptor [5]. From this homology it was named the LDL recep- tor-related protein or LRP. This protein contains four extracellular domains which resemble the ligand-bind- ing region of the LDL receptor, including clusters of the highly acidic class A cysteine-rich motifs which have been postulated to be directly involved in the interac- tion with apoE and apoB in LDL particles [6,7]. ApoE- containing ligands have indeed been shown to interact preferentially with LRP molecules on the surface of cells [8], and in cells devoid of a functional LDL receptor the LRP is capable of mediating the uptake of apoE-enriched lipoproteins [9], making it probable that one function of the LRP is as an apoE receptor. A possible iigand for the LRP is therefore the chylomicron remnant, although no direct binding has yet been dem- onstrated. It is unlikely that the sole function of the LRP is in remnant binding, however, because it is found in most tissues [5] and tissue culture cell lines (unpub- lished data) even though chylomicron remnant uptake occurs principally in liver. Direct experiments to in- vestigate the function of the LRP are technically dif- ficult due to the large size of the protein (for purifica- tion) and cDNA (for transfection), but circumstantial evidence in favour of LRP binding to chylomicron remnants comes from the EDTA resistance of binding to apoE iiposomes [8] which is a property of remnant uptake [10]. One further expected property of a Division)