Key Specifications Table
|Species Reactivity||Key Applications||Host||Format||Antibody Type|
|H||IP, WB||Gt||Serum||Polyclonal Antibody|
|Description||Anti-Apolipoprotein B Antibody|
|Presentation||Defibrinated, delipidized and absorbed by solid phase chromatography as required. Goat antisera in 0.05M Tris-HCl pH 7.5, 0.5M NaCl with 0.1% sodium azide.|
|Safety Information according to GHS|
|Storage and Shipping Information|
|Storage Conditions||Maintain at -20°C in undiluted aliquots for up to 12 months. Avoid repeated freeze/thaw cycles.|
|Material Size||1 mL|
|GOAT ANTI-APOLIPOPROTEIN B POLYCLONAL ANTIBODY - 2390374||2390374|
|GOAT ANTI-APOLIPOPROTEIN B - 2492087||2492087|
|GOAT ANTI-APOLIPOPROTEIN B -2519232||2519232|
|GOAT ANTI-APOLIPOPROTEIN B -2573577||2573577|
|GOAT ANTI-APOLIPOPROTEIN B -2592702||2592702|
|GOAT ANTI-APOLIPOPROTEIN B -2668097||2668097|
|GOAT ANTI-APOLIPOPROTEIN B -2722844||2722844|
|GOAT ANTI-APOLIPOPROTEIN B -2788897||2788897|
|GOAT ANTI-APOLIPOPROTEIN B POLYCLONAL ANTIBODY -2499546||2499546|
|Reference overview||Pub Med ID|
|Identification of protein disulfide isomerase 1 as a key isomerase for disulfide bond formation in apolipoprotein B100.|
Wang, S; Park, S; Kodali, VK; Han, J; Yip, T; Chen, Z; Davidson, NO; Kaufman, RJ
Molecular biology of the cell 26 594-604 2015
Apolipoprotein (apo) B is an obligatory component of very low density lipoprotein (VLDL), and its cotranslational and posttranslational modifications are important in VLDL synthesis, secretion, and hepatic lipid homeostasis. ApoB100 contains 25 cysteine residues and eight disulfide bonds. Although these disulfide bonds were suggested to be important in maintaining apoB100 function, neither the specific oxidoreductase involved nor the direct role of these disulfide bonds in apoB100-lipidation is known. Here we used RNA knockdown to evaluate both MTP-dependent and -independent roles of PDI1 in apoB100 synthesis and lipidation in McA-RH7777 cells. Pdi1 knockdown did not elicit any discernible detrimental effect under normal, unstressed conditions. However, it decreased apoB100 synthesis with attenuated MTP activity, delayed apoB100 oxidative folding, and reduced apoB100 lipidation, leading to defective VLDL secretion. The oxidative folding-impaired apoB100 was secreted mainly associated with LDL instead of VLDL particles from PDI1-deficient cells, a phenotype that was fully rescued by overexpression of wild-type but not a catalytically inactive PDI1 that fully restored MTP activity. Further, we demonstrate that PDI1 directly interacts with apoB100 via its redox-active CXXC motifs and assists in the oxidative folding of apoB100. Taken together, these findings reveal an unsuspected, yet key role for PDI1 in oxidative folding of apoB100 and VLDL assembly.
|The endoplasmic reticulum coat protein II transport machinery coordinates cellular lipid secretion and cholesterol biosynthesis.|
Fryer, LG; Jones, B; Duncan, EJ; Hutchison, CE; Ozkan, T; Williams, PA; Alder, O; Nieuwdorp, M; Townley, AK; Mensenkamp, AR; Stephens, DJ; Dallinga-Thie, GM; Shoulders, CC
The Journal of biological chemistry 289 4244-61 2014
Triglycerides and cholesterol are essential for life in most organisms. Triglycerides serve as the principal energy storage depot and, where vascular systems exist, as a means of energy transport. Cholesterol is essential for the functional integrity of all cellular membrane systems. The endoplasmic reticulum is the site of secretory lipoprotein production and de novo cholesterol synthesis, yet little is known about how these activities are coordinated with each other or with the activity of the COPII machinery, which transports endoplasmic reticulum cargo to the Golgi. The Sar1B component of this machinery is mutated in chylomicron retention disorder, indicating that this Sar1 isoform secures delivery of dietary lipids into the circulation. However, it is not known why some patients with chylomicron retention disorder develop hepatic steatosis, despite impaired intestinal fat malabsorption, and why very severe hypocholesterolemia develops in this condition. Here, we show that Sar1B also promotes hepatic apolipoprotein (apo) B lipoprotein secretion and that this promoting activity is coordinated with the processes regulating apoB expression and the transfer of triglycerides/cholesterol moieties onto this large lipid transport protein. We also show that although Sar1A antagonizes the lipoprotein secretion-promoting activity of Sar1B, both isoforms modulate the expression of genes encoding cholesterol biosynthetic enzymes and the synthesis of cholesterol de novo. These results not only establish that Sar1B promotes the secretion of hepatic lipids but also adds regulation of cholesterol synthesis to Sar1B's repertoire of transport functions.
|Exon skipping of hepatic APOB pre-mRNA with splice-switching oligonucleotides reduces LDL cholesterol in vivo.|
Disterer, P; Al-Shawi, R; Ellmerich, S; Waddington, SN; Owen, JS; Simons, JP; Khoo, B
Molecular therapy : the journal of the American Society of Gene Therapy 21 602-9 2013
Familial hypercholesterolemia (FH) is a genetic disorder characterized by extremely high levels of plasma low-density lipoprotein (LDL), due to defective LDL receptor-apolipoprotein B (APOB) binding. Current therapies such as statins or LDL apheresis for homozygous FH are insufficiently efficacious at lowering LDL cholesterol or are expensive. Treatments that target APOB100, the structural protein of LDL particles, are potential therapies for FH. We have developed a series of APOB-directed splice-switching oligonucleotides (SSOs) that cause the expression of APOB87, a truncated isoform of APOB100. APOB87, like similarly truncated isoforms expressed in patients with a different condition, familial hypobetalipoproteinemia, lowers LDL cholesterol by inhibiting very low-density lipoprotein (VLDL) assembly and increasing LDL clearance. We demonstrate that these "APO-skip " SSOs induce high levels of exon skipping and expression of the APOB87 isoform, but do not substantially inhibit APOB48 expression in cell lines. A single injection of an optimized APO-skip SSO into mice transgenic for human APOB resulted in abundant exon skipping that persists for greater than 6 days. Weekly treatments generated a sustained reduction in LDL cholesterol levels of 34-51% in these mice, superior to pravastatin in a head-to-head comparison. These results validate APO-skip SSOs as a candidate therapy for FH.
|Erythrocyte-bound apolipoprotein B in relation to atherosclerosis, serum lipids and ABO blood group.|
Klop, B; van de Geijn, GJ; Bovenberg, SA; van der Meulen, N; Elte, JW; Birnie, E; Njo, TL; Janssen, HW; van Miltenburg, A; Jukema, JW; Cabezas, MC
PloS one 8 e75573 2013
Erythrocytes carry apolipoprotein B on their membrane, but the determining factors of erythrocyte-bound apolipoprotein B (ery-apoB) are unknown. We aimed to explore the determinants of ery-apoB to gain more insight into potential mechanisms.Subjects with and without CVD were included (N = 398). Ery-apoB was measured on fresh whole blood samples using flow cytometry. Subjects with ery-apoB levels ≤ 0.20 a.u. were considered deficient. Carotid intima media thickness (CIMT) was determined as a measure of (subclinical) atherosclerosis.Mean ery-apoB value was 23.2% lower in subjects with increased CIMT (0.80 ± 0.09 mm, N = 140) compared to subjects with a normal CIMT (0.57 ± 0.08 mm, N = 258) (P = 0.007, adjusted Pless than 0.001). CIMT and ery-apoB were inversely correlated (Spearman's r: -0.116, P = 0.021). A total of 55 subjects (13.6%) were considered ery-apoB deficient, which was associated with a medical history of CVD (OR: 1.86, 95% CI 1.04-3.33; adjusted OR: 1.55; 95% CI 0.85-2.82). Discontinuation of statins in 54 subjects did not influence ery-apoB values despite a 58.4% increase in serum apolipoprotein B. Subjects with blood group O had significantly higher ery-apoB values (1.56 ± 0.94 a.u.) when compared to subjects with blood group A (0.89 ± 1.15 a.u), blood group B (0.73 ± 0.1.12 a.u.) or blood group AB (0.69 ± 0.69 a.u.) (P-ANOVA = 0.002).Absence or very low values of ery-apoB are associated with clinical and subclinical atherosclerosis. While serum apolipoprotein B is not associated with ery-apoB, the ABO blood group seems to be a significant determinant.
|Opposing roles of cell death-inducing DFF45-like effector B and perilipin 2 in controlling hepatic VLDL lipidation.|
Li, X; Ye, J; Zhou, L; Gu, W; Fisher, EA; Li, P
Journal of lipid research 53 1877-89 2012
Regulation of hepatic very low density lipoprotein (VLDL) assembly and maturation is crucial in controlling lipid homeostasis and in the development of metabolic disorders, including obesity, hepatic steatosis, and insulin resistance. Cideb, a member of cell death-inducing DFF45-like effector (CIDE) protein family, has been previously shown to promote VLDL lipidation and maturation. However, the precise subcellular location of Cideb-mediated VLDL lipidation and the factors modulating its activity remain elusive. In addition to its localization to endoplasmic reticulum (ER) and lipid droplets (LD), we observed that Cideb was also localized to the Golgi apparatus. Mature and lipid-rich VLDL particles did not accumulate in the Golgi apparatus in Cideb(-/-) livers. Interestingly, we observed that hepatic perilipin 2/adipose differentiation-related protein (ADRP) levels were markedly increased in Cideb(-/-) mice. Liver-specific knockdown of perilipin 2 in Cideb(-/-) mice resulted in the reduced accumulation of hepatic triglycerides (TAG), increased VLDL-TAG secretion, and the accumulation of mature TAG-rich VLDL in the Golgi apparatus. These data reveal that Cideb and perilipin 2 play opposing roles in controlling VLDL lipidation and hepatic lipid homeostasis.
|Ubiquitination regulates the assembly of VLDL in HepG2 cells and is the committing step of the apoB-100 ERAD pathway.|
Fisher, EA; Khanna, NA; McLeod, RS
Journal of lipid research 52 1170-80 2011
Apolipoprotein B-100 (apoB-100) is degraded by endoplasmic reticulum-associated degradation (ERAD) when lipid availability limits assembly of VLDLs. The ubiquitin ligase gp78 and the AAA-ATPase p97 have been implicated in the proteasomal degradation of apoB-100. To study the relationship between ERAD and VLDL assembly, we used small interfering RNA (siRNA) to reduce gp78 expression in HepG2 cells. Reduction of gp78 decreased apoB-100 ubiquitination and cytosolic apoB-ubiquitin conjugates. Radiolabeling studies revealed that gp78 knockdown increased secretion of newly synthesized apoB-100 and, unexpectedly, enhanced VLDL assembly, as the shift in apoB-100 density in gp78-reduced cells was accompanied by increased triacylglycerol (TG) secretion. To explore the mechanisms by which gp78 reduction might enhance VLDL assembly, we compared the effects of gp78 knockdown with those of U0126, a mitogen-activated protein kinase/ERK kinase1/2 inhibitor that enhances apoB-100 secretion in HepG2 cells. U0126 treatment increased secretion of both apoB100 and TG and decreased the ubiquitination and cellular accumu-lation of apoB-100. Furthermore, p97 knockdown caused apoB-100 to accumulate in the cell, but if gp78 was concomitantly reduced or assembly was enhanced by U0126 treatment, cellular apoB-100 returned toward baseline. This indicates that ubiquitination commits apoB-100 to p97-mediated retrotranslocation during ERAD. Thus, decreasing ubiquitination of apoB-100 enhances VLDL assembly, whereas improving apoB-100 lipidation decreases its ubiquitination, suggesting that ubiquitination has a regulatory role in VLDL assembly.
|Lipoprotein profiles in SCID/uPA mice transplanted with human hepatocytes become human-like and correlate with HCV infection success.|
Steenbergen, RH; Joyce, MA; Lund, G; Lewis, J; Chen, R; Barsby, N; Douglas, D; Zhu, LF; Tyrrell, DL; Tyrrell, DL; Kneteman, NM
American journal of physiology. Gastrointestinal and liver physiology 299 G844-54 2010
Although multiple determinants for hepatitis C virus (HCV) infection are known, it remains partly unclear what determines the human specificity of HCV infection. Presumably, the presence of appropriate entry receptors is essential, and this may explain why HCV is unable to infect nonhuman hepatocytes. However, using mice with chimeric human livers, we show in this study that the presence of human hepatocytes, and therefore human entry receptors, is not sufficient for HCV infection. In successfully transplanted SCID/Alb-uPA mice, infection with HCV is reliable only when ∼70-80% of the liver consists of human hepatocytes. We show that chimeric mice, which are hard to infect with HCV, have significant groups of human hepatocytes that are readily infected with hepatitis B virus. Thus it is unlikely that the lack of infection with HCV can simply be attributed to low hepatocyte numbers. We investigated whether the humanization of lipoprotein profiles is positively associated with infection success. We show that the lipoprotein profiles of chimeric mice become more human-like at high levels of engraftment of human hepatocytes. This and expression of markers of human lipoprotein biosynthesis, human apolipoprotein B (ApoB) and cholesterol ester transfer protein (CETP), show a strong positive correlation with successful infection. Association of HCV in the blood of chimeric mice to ApoB-containing lipoproteins is comparable to association of HCV in patient serum and provides further support for a critical role for ApoB-containing lipoproteins in the infectious cycle of HCV. Our data suggest that the weakest link in the HCV infection chain does not appear to be the presence of human hepatocytes per se. We believe that HCV infection also depends on the presence of sufficient levels of human lipoproteins.
|The AAA-ATPase p97 facilitates degradation of apolipoprotein B by the ubiquitin-proteasome pathway.|
Fisher, EA; Lapierre, LR; Junkins, RD; McLeod, RS
Journal of lipid research 49 2149-60 2008
The ATPase associated with various cellular activities (AAA-ATPase) p97 (p97) has been implicated in the retrotranslocation of target proteins for delivery to the cytosolic proteasome during endoplasmic reticulum-associated degradation (ERAD). Apolipoprotein B-100 (apoB-100) is an ERAD substrate in liver cells, including the human hepatoma, HepG2. We studied the potential role of p97 in the ERAD of apoB-100 in HepG2 cells using cell permeabilization, coimmunoprecipitation, and gene silencing. Degradation was abolished when HepG2 cytosol was removed by digitonin permeabilization, and treatment of intact cells with the proteasome inhibitor MG132 caused accumulation of ubiquitinated apoB protein in the cytosol. Cross-linking of intact cells with the thiol-cleavable agent dithiobis(succinimidylpropionate) (DSP), as well as nondenaturing immunoprecipitation, demonstrated an interaction between p97 and intracellular apoB. Small interfering ribonucleic acid (siRNA)-mediated reduction of p97 protein increased the intracellular levels of newly synthesized apoB-100, predominantly because of a decrease in the turnover of newly synthesized apoB-100 protein. However, although the posttranslational degradation of newly synthesized apoB-100 was delayed by p97 knockdown, secretion of apoB-100 was not affected. Knockdown of p97 also impaired the release of apoB-100 and polyubiquitinated apoB into the cytosol. In summary, our results suggest that retrotranslocation and proteasomal degradation of apoB-100 can be dissociated in HepG2 cells, and that the AAA-ATPase p97 is involved in the removal of full-length apoB from the biosynthetic pathway to the cytosolic proteasome.
|Antisense oligonucleotide-induced alternative splicing of the APOB mRNA generates a novel isoform of APOB.|
Khoo, B; Roca, X; Chew, SL; Krainer, AR
BMC molecular biology 8 3 2007
Apolipoprotein B (APOB) is an integral part of the LDL, VLDL, IDL, Lp(a) and chylomicron lipoprotein particles. The APOB pre-mRNA consists of 29 constitutively-spliced exons. APOB exists as two natural isoforms: the full-length APOB100 isoform, assembled into LDL, VLDL, IDL and Lp(a) and secreted by the liver in humans; and the C-terminally truncated APOB48, assembled into chylomicrons and secreted by the intestine in humans. Down-regulation of APOB100 is a potential therapy to lower circulating LDL and cholesterol levels.We investigated the ability of 2'O-methyl RNA antisense oligonucleotides (ASOs) to induce the skipping of exon 27 in endogenous APOB mRNA in HepG2 cells. These ASOs are directed towards the 5' and 3' splice-sites of exon 27, the branch-point sequence (BPS) of intron 26-27 and several predicted exonic splicing enhancers within exon 27. ASOs targeting either the 5' or 3' splice-site, in combination with the BPS, are the most effective. The splicing of other alternatively spliced genes are not influenced by these ASOs, suggesting that the effects seen are not due to non-specific changes in alternative splicing. The skip 27 mRNA is translated into a truncated isoform, APOB87SKIP27.The induction of APOB87SKIP27 expression in vivo should lead to decreased LDL and cholesterol levels, by analogy to patients with hypobetalipoproteinemia. As intestinal APOB mRNA editing and APOB48 expression rely on sequences within exon 26, exon 27 skipping should not affect APOB48 expression unlike other methods of down-regulating APOB100 expression which also down-regulate APOB48.Full Text Article
|Bile Acid Reduces the Secretion of Very Low Density Lipoprotein by Repressing Microsomal Triglyceride Transfer Protein Gene Expression Mediated by Hepatocyte Nuclear Factor-4|
Hirokane, H. et al.
J Biol Chem., 279 (44):45685-45692 (2004) 2004
|Anti-Apolipoprotein B - Data Sheet|