ApoE, a main apoprotein of the chylomicron, binds to a specific receptor on liver cells and peripheral cells.
NCBI Summary:
The protein encoded by this gene is a major apoprotein of the chylomicron. It binds to a specific liver and peripheral cell receptor, and is essential for the normal catabolism of triglyceride-rich lipoprotein constituents. This gene maps to chromosome 19 in a cluster with the related apolipoprotein C1 and C2 genes. Mutations in this gene result in familial dysbetalipoproteinemia, or type III hyperlipoproteinemia (HLP III), in which increased plasma cholesterol and triglycerides are the consequence of impaired clearance of chylomicron and VLDL remnants. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2014]
General function
Comment
Cellular localization
Secreted
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Apolipoprotein E-containing HDL-associated platelet-activating factor acetylhydrolase activities and malondialdehyde concentrations in patients with PCOS. Fan P et al. (2012) PAF and PAF-like oxidized phospholipids hydrolysed by platelet-activating factor (PAF) acetylhydrolase (AH) are potent lipid mediators involved in inflammation and atherosclerosis. Apolipoprotein (apo) E-containing high-density lipoprotein (HDL) has antioxidant, anti-inflammatory and anti-atherogenic properties. The study investigated apoE-containing HDL-associated PAF-AH (HDL-PAF-AH) and total (apoE-containing+apoE-poor) HDL-PAF-AH activities as well as malondialdehyde (MDA) concentration in 291 patients with polycystic ovary syndrome (PCOS) using the Rotterdam consensus criteria and 281 control women. Compared with the control women, patients with hyperandrogenism+oligo/anovulation+polycystic ovaries (PCO) or hyperandrogenism+PCO had lower total, apoE-containing and apoE-poor HDL-PAF-AH activities, while those with oligo/anovulation+PCO showed decreased total and apoE-poor HDL-PAF-AH activities. Other factors including insulin resistance and obesity in PCOS had the adverse effects associated with the HDL-PAF-AH activities. Serum MDA concentration was associated with PCOS, hyperandrogenism, insulin resistance and hypertriglyceridaemia in patients with PCOS. Decreased total and apoE-containing HDL-PAF-AH activities and increased serum MDA concentration may contribute to the pathogenesis of PCOS and potentially link to related complications responsible for oxidative stress and inflammation such as an increased risk for type 2 diabetes mellitus and/or future cardiovascular diseases in PCOS patients.//////////////////
Ovarian function
Follicle atresia
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Expression regulated by
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Ovarian localization
Granulosa, Theca
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Zerbinatti CV, et al 2001 reported that apolipoprotein E is a putative autocrine regulator of the rat
ovarian theca cell compartment.
Apolipoprotein (apo) E inhibits androgen production by ovarian theca cells. A synthetic peptide mimicked the full-size protein
induced theca and interstitial cell (TIC) apoptosis indicated by pyknotic cell
morphology, increased DNA end-labeling (TUNEL), and DNA ladders. Theca cells of atretic follicles express the
greatest apo E mRNA, and cultured TIC produce apo E. When
considered with the observation of TUNEL-positive theca cells in atretic
follicles these results support the hypothesis that intraovarian apo E
controls theca cell production of androgen as well as limiting the size of the
theca cell compartment.
Identification of new proteins in follicular fluid from mature human follicles by direct sample rehydration method of two-dimensional polyacrylamide gel electrophoresis Lee HC, et al .
Human follicular fluid (HFF) includes various biologically active proteins which can affect follicle growth and oocyte fertilization. Thus far, these proteins from mature follicles in human follicular fluid have been poorly characterized. Here, two-dimensional polyacrylamide gel electrophoresis (2-DE) with matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) was used to identify new proteins in HFF. Mature follicular fluids were obtained from five females after oocyte collection during in vitro fertilization (IVF). We directly rehydrated HFF samples, obtained high-resolution 2-DE maps, and processed them for 2-DE and MALDI-MS. One hundred eighty spots were detected and 10 of these spots were identified. By the 2-DE database, six of them had been reported, as proteins already existing in HFF. Hormone sensitive lipase (HSL), Unnamed protein product 1 (UPP1), Unnamed protein product 2 (UPP2), and apolipoprotein A-IV precursor were newly detected. HSL and apolipoprotein A-IV participate in lipid metabolism. UPP1 has a homology with selenocysteine lyase. We found by RT-PCR that these genes are expressed from human primary granulosa cells. The proteins identified here may emerge as potential candidates for specific functions during folliculogenesis, hormone secretion regulation, or oocyte maturation. Further functional analysis of these proteins is necessitated to determine their biological implications.