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Methods in Enzymology 1996
Topics: Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Blood Proteins; Centrifugation, Density Gradient; Densitometry; Electrophoresis, Polyacrylamide Gel; Humans; Lipoproteins, LDL; Reference Standards; Sodium Dodecyl Sulfate; Ultracentrifugation
PubMed: 8749002
DOI: 10.1016/s0076-6879(96)63007-9 -
Lancet (London, England) May 1988
Topics: Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Arteriosclerosis; Humans; Lipid Metabolism; Receptors, LDL
PubMed: 2896961
DOI: No ID Found -
Journal of Lipid Research Jul 1994The present work describes a procedure for determining apolipoproteins (apo) B-100 and B-48 in subfractions of triglyceride-rich lipoproteins by analytical sodium...
The present work describes a procedure for determining apolipoproteins (apo) B-100 and B-48 in subfractions of triglyceride-rich lipoproteins by analytical sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with Coomassie staining. The chromogenicity of the two apoB species was found to be almost equal, and independent of lipoprotein particle size. Both proteins were sensitive to overloading of the gel, which resulted in low dye uptake. This was particularly evident for apoB-48. The precision of this analytical SDS-PAGE-based procedure to determine the plasma concentrations of apoB-100 and B-48 in triglyceride-rich lipoproteins was found to be appreciably low (coefficients of variation ranging between 3.1 and 14.1%).
Topics: Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Electrophoresis, Polyacrylamide Gel; Evaluation Studies as Topic; Humans; Lipoproteins; Reproducibility of Results; Sensitivity and Specificity; Triglycerides
PubMed: 7964192
DOI: No ID Found -
Circulation Nov 1990For the past 5 years, investigators from many different laboratories have contributed to a greatly increased understanding of two very important lipid-carrying proteins... (Review)
Review
For the past 5 years, investigators from many different laboratories have contributed to a greatly increased understanding of two very important lipid-carrying proteins in plasma--apo B-100 and apo B-48. Apo B-100, an extremely large protein composed of 4,536 amino acids, is synthesized by the liver and is crucial for the assembly of triglyceride-rich VLDL particles. Apo B-100 is virtually the only protein of LDL, a cholesteryl ester-enriched class of lipoproteins that are metabolic products of VLDL. The apo B-100 of LDL serves as a ligand for the LDL receptor-mediated uptake of LDL particles by the liver and extrahepatic tissues. The LDL receptor-binding region of apo B-100 is located in the carboxyterminal portion of the molecule, whereas its lipid-binding regions appear to be broadly dispersed throughout its length. Apo B-48 contains the amino-terminal 2,152 amino acids of apo B-100 and is produced by the intestine as a result of editing of a single nucleotide of the apo B mRNA, which changes the codon specifying apo B-100 amino acid 2,153 to a premature stop codon. Apo B-48 has an obligatory structural role in the formation of chylomicrons; therefore, its synthesis is essential for absorption of dietary fats and fat-soluble vitamins. Both apo B-48 and apo B-100 are encoded on chromosome 2 by a single gene that contains 29 exons and 28 introns. An elevated level of apo B-100 in the plasma is a potent risk factor for developing premature atherosclerotic disease. In the past 3 years, many different apo B gene mutations that affect the concentrations of both apo B and cholesterol in the plasma have been characterized. A missense mutation in the codon for apo B-100 amino aid 3,500 is associated with hypercholesterolemia. This mutation results in poor binding of apo B-100 to the LDL receptor, thereby causing the cholesteryl ester-enriched LDL particles to accumulate in the plasma. This disorder is called familial defective apo B-100, and it is probably a cause of premature atherosclerotic disease. Familial hypobetalipoproteinemia is a condition associated with abnormally low levels of apo B and cholesterol; affected individuals may actually have a reduced risk of atherosclerotic disease.(ABSTRACT TRUNCATED AT 400 WORDS)
Topics: Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Cholesterol; Genetic Variation; Humans; Hyperlipoproteinemias; Hypolipoproteinemias; Mutation; Polymorphism, Restriction Fragment Length
PubMed: 1977530
DOI: 10.1161/01.cir.82.5.1574 -
Metabolism: Clinical and Experimental Jan 2024Epidemiological evidence links the proprotein convertase subtilisin/kexin 7 (PCSK7) to triglyceride (TG) metabolism. We associated the known PCSK7 gain-of-function...
BACKGROUND
Epidemiological evidence links the proprotein convertase subtilisin/kexin 7 (PCSK7) to triglyceride (TG) metabolism. We associated the known PCSK7 gain-of-function non-coding SNP rs236918 with higher levels of plasma apolipoprotein B (apoB) and the loss-of-function coding variant p.Pro777Leu (SNP rs201598301) with lower apoB and TG. Herein, we aimed to unravel the in vivo role of liver PCSK7.
METHODS
We biochemically defined the functional role of PCSK7 in lipid metabolism using hepatic cell lines and Pcsk7 mice. Our findings were validated following subcutaneous administration of hepatocyte-targeted N-acetylgalactosamine (GalNAc)-antisense oligonucleotides (ASOs) against Pcsk7.
RESULTS
Independent of its proteolytic activity, membrane-bound PCSK7 binds apoB100 in the endoplasmic reticulum and enhances its secretion. Mechanistically, the loss of PCSK7/Pcsk7 leads to apoB100 degradation, triggering an unfolded protein response, autophagy, and β-oxidation, eventually reducing lipid accumulation in hepatocytes. Non-alcoholic fatty liver disease (NAFLD) was induced by a 12-week high fat/fructose/cholesterol diet in wild type (WT) and Pcsk7 mice that were then allowed to recover on a 4-week control diet. Pcsk7 mice recovered more effectively than WT mice from all NAFLD-related liver phenotypes. Finally, subcutaneous administration of GalNAc-ASOs targeting hepatic Pcsk7 to WT mice validated the above results.
CONCLUSIONS
Our data reveal hepatic PCSK7 as one of the major regulators of apoB, and its absence reduces apoB secretion from hepatocytes favoring its ubiquitination and degradation by the proteasome. This results in a cascade of events, eventually reducing hepatic lipid accumulation, thus supporting the notion of silencing PCSK7 mRNA in hepatocytes for targeting NAFLD.
Topics: Mice; Animals; Non-alcoholic Fatty Liver Disease; Subtilisin; Triglycerides; Liver; Apolipoproteins B; Proprotein Convertases; Apolipoprotein B-100
PubMed: 37967646
DOI: 10.1016/j.metabol.2023.155736 -
Trends in Cardiovascular Medicine 1999It generally is assumed that lipoproteins containing apolipoprotein B (apo B) are secreted only by the intestine and the liver. However, we recently demonstrated that... (Review)
Review
It generally is assumed that lipoproteins containing apolipoprotein B (apo B) are secreted only by the intestine and the liver. However, we recently demonstrated that the human apo-B gene also is expressed in the hearts of human apo-B transgenic mice and in human heart tissue. Using metabolic labeling techniques, we showed that heart tissue from human apo-B transgenic mice and nontransgenic mice, as well as human heart tissue, synthesize and secrete apo-B-containing lipoproteins. The reason why the heart makes lipoproteins is unknown, but we hypothesized that the heart may use lipoprotein synthesis to unload surplus cellular lipids, particularly triglycerides, which are not immediately required for mitochondrial beta-oxidation.
Topics: Animals; Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Biomarkers; Cells, Cultured; Gene Expression; Golgi Apparatus; Heart; Humans; Lipoproteins; Mice; Mice, Transgenic; Myocardium
PubMed: 10578525
DOI: 10.1016/s1050-1738(99)00011-0 -
Annals of Medicine Dec 1993Apolipoprotein B (apo B) circulates in two distinct forms referred to as apo B100 and apo B48. Apo B48 is colinear with the amino-terminal half of apo B100 and arises as... (Review)
Review
Apolipoprotein B (apo B) circulates in two distinct forms referred to as apo B100 and apo B48. Apo B48 is colinear with the amino-terminal half of apo B100 and arises as a result of a post-transcriptional modification, termed apo B mRNA editing. This process changes a single cytidine nucleotide in apo B100 mRNA thereby altering a CAA codon, encoding glutamine in apo B100, to a UAA codon, which specifies an in-frame stop codon in apo B48. The functional consequences of apo B mRNA editing include the divergent catabolism of plasma lipoproteins expressing either apo B100 or B48, and also the ability to generate the hybrid lipoprotein, Lp(a). These differences arise because the requisite regions of apo B for interaction either with the low-density lipoprotein receptor or with apolipoprotein (a) are contained within the carboxyl terminus of apo B100. Apo B mRNA editing is regulated by species, tissue and cell-specific factors, one of which has been recently cloned. The further characterization of apo B mRNA editing, the first example of a mammalian gene regulated by post-transcriptional nucleotide alteration, will be important for an understanding of lipoprotein assembly.
Topics: APOBEC-1 Deaminase; Animals; Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Cloning, Molecular; Codon; Cytidine Deaminase; Humans; Intestine, Small; Liver; Organ Specificity; RNA Editing; Rats; Sequence Analysis, RNA
PubMed: 8292303
DOI: No ID Found -
Nihon Rinsho. Japanese Journal of... Sep 1999
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Reviews in Endocrine & Metabolic... Dec 2004
Review
Topics: Animals; Apolipoproteins B; Biological Transport; Carrier Proteins; Gene Expression Regulation; Homeostasis; Humans; Insulin Resistance; Lipids; Lipoproteins, VLDL; Liver; Molecular Chaperones; Protein Biosynthesis; Signal Transduction
PubMed: 15486461
DOI: 10.1023/B:REMD.0000045100.66675.92 -
Biochimie 1995Apolipoprotein (apo) B mRNA editing consists of a C-->U conversion of the first base of the codon CAA encoding glutamine 2153 in apoB mRNA to UAA, a stop codon. The cDNA... (Review)
Review
Apolipoprotein (apo) B mRNA editing consists of a C-->U conversion of the first base of the codon CAA encoding glutamine 2153 in apoB mRNA to UAA, a stop codon. The cDNA for an apoB mRNA editing protein was recently cloned in rat and human. The human protein contains 236 amino acid residues and exists as a homodimer. The editing protein edits apoB mRNA in vitro only in the presence of tissue complementation factors. There is a leucine-rich motif spanning residues 173-210 of the protein which may be involved in homodimer formation and/or interaction with complementation factors. The requirements for these factors support the existence of an editosome involved in apoB mRNA editing.
Topics: APOBEC-1 Deaminase; Apolipoprotein B-100; Apolipoprotein B-48; Apolipoproteins B; Codon; Cytidine Deaminase; Humans; Lipoproteins; RNA Editing; RNA, Messenger
PubMed: 7599279
DOI: 10.1016/0300-9084(96)88107-7