Mouse Very‐Low‐Density‐Lipoprotein Receptor (VLDLR) cDNA Cloning, Tissue‐specific Expression and Evolutionary Relationship with the Low‐density‐lipoprotein Receptor

Abstract

The very-low-density-lipoprotein receptor (VLDLR) is a recently described lipoprotein receptor that shows considerable similarity to the low-density-lipoprotein receptor (LDLR). This receptor has been suggested to be important for the metabolism of apoprotein-E-containing triacylglycerolrich lipoproteins, such as very-low-density-lipoprotein (VLDL), P-migrating VLDL and intermediate-density lipoprotein. cDNA clones that code for the VLDLR were isolated from a mouse heart cDNA library. The deduced amino acid sequence predicts a mature protein of 846 amino acids preceded by a 27-residue signal peptide. Three mRNA species for the VLDLR with sizes of 3.9, 4.5 and 7.9 kilobases were present in high concentration in heart and muscle, which utilize triacylglycerols as an energy source. VLDLR mRNA is also detected in decreasing amounts in kidney, brain, ovary, testis, lung and adipose tissue. It is essentially absent in liver and small intestine. The amino acid sequence of the VLDLR is highly conserved among rabbit, human and mouse. VLDLR contains five structural domains very similar to those in LDLR, except that the ligand-binding domain in VLDLR has an eightfold repeat instead of a sevenfold repeat in LDLR. Sequence conservation among animal species is much higher for the VLDLR than the LDLR. Sequences of the VLDLR from three vertebrate species and the LDLR from five vertebrate species were aligned and a phylogenetic tree was reconstructed. Although both receptors contain five domains and share amino acid sequence similarity, our computations showed that they diverged before the divergence between mammals and amphibians. In addition, sequence comparison of both receptor sequences suggests that the rabbit is evolutionarily closer to man than to the mouse. These results are consistent with the hypothesis that the VLDLR and the LDLR have evolved from a common ancestral gene to play distinct roles in lipoprotein metabolism and that the metabolic handling of triacylglycerol by the body via the VLDLR is a highly conserved mechanism.Lipoprotein receptors play pivotal roles in the metabolism of triacylglycerols and cholesterol . The best characterized of the lipoprotein receptors is the low-density-lipoprotein receptor (LDLR). The LDLR binds to the apolipoprotein (apo) B-100-containing low-density-lipoproteins (LDL), as well as apoprotein-Econtaining lipoproteins such as intermediate-density lipoproteins (IDL), P-migrating very-low-density lipoproteins @-VLDL) and a cholesterol-induced high-density lipoprotein, which contains apoE as its sole apolipoprotein (Esser et al.,

Hepatitis C virus utilizes VLDLR as a novel entry pathway

“…The discovery of the involvement of mouse VLDLR in HCV entry in Huh7.5#26 cells raised the question of whether HCV entry into mouse hepatocytes occurs exclusively via the CD81-dependent pathway. VLDLR expression was not observed in the mouse liver (26), and we confirmed this result (Fig. S9A).…”

Regulation of the Ligand Binding Activity of the Human Very Low Density Lipoprotein Receptor by Protein Kinase C-dependent Phosphorylation

“…More recently, however, Bu et al (81) demonstrate that the LDL receptor-related protein/␣ 2 -macroglobulin receptor is phosphorylated in neuronal cells in response to nerve growth factor, leading to enhanced expression and endocytic activity. Our studies suggest that the cytoplasmic domain of the VLDL-R plays an important role in regulating receptor function, a hypothesis consistent with the complete sequence conservation of this domain in the murine (38,82), rabbit (6), and human (35-37) receptors. Trommsdorf et al (83) also demonstrate a critical role for the cytoplasmic domains of the VLDL-R and apoE receptor 2 in binding of the cytoplasmic adaptor protein mammalian Disabled (mDab1), an interaction critical for appropriate migration and layering of neurons during development of the cerebellum and cerebral cortex.…”

“…For selected studies, RAP was conjugated to cyanogen bromide-activated Sepharose 4B (8.9 mg/ml of packed beads) per the manufacturer's protocol (Amersham Pharmacia Biotech) or labeled with 125 I to a specific activity of ϳ5.0 ϫ 10 6 cpm/g using iodobeads. Affinity-purified anti-VLDL receptor antibodies, raised against a peptide corresponding to the C-terminal 20 amino acids of the human (35-37) mouse (38) and rabbit (6) VLDL-R, have been described (30). A rabbit antibody raised against a polypeptide encompassing the 160 N-terminal amino acids of the VLDL-R (25) was used for detection of a truncated VLDL-R mutant lacking the cytoplasmic domain.…”

Upregulation of hepatic VLDLR via PPARα is required for the triglyceride-lowering effect of fenofibrate

“…The VLDL receptor (VLDLR), a member of the LDL receptor (LDLR) family, is widely expressed in the heart, skeletal muscles, adipose tissues, and macrophages ( 14,15 ). However, its levels are barely detectable in the liver under normal conditions.…”