Apolipoprotein C Iii Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Apolipoprotein C-III (APOC3) is a 79-amino acid protein component of very-low-density lipoproteins (VLDL) and high-density lipoproteins (HDL). It plays a central role in regulating plasma triglyceride levels by inhibiting lipoprotein lipase and hepatic uptake of triglyceride-rich lipoproteins. APOC3 is predominantly synthesized in the liver and to a lesser extent in the intestine, where it is secreted and associates with circulating lipoprotein particles. The protein is a key regulator of lipid metabolism and has emerged as an important therapeutic target for cardiovascular disease and potentially neurodegenerative conditions.
| Attribute |
Value |
| Gene Symbol |
APOC3 |
| Protein Name |
Apolipoprotein C-III |
| Molecular Weight |
~8.8 kDa (79 amino acids) |
| Aliases |
ApoC-III |
| UniProt ID |
P02656 |
| Tissue Expression |
Liver (primary), intestine (minor) |
APOC3 is a small apolipoprotein with several structural domains:
- Amphipathic Alpha-Helices: Two major helical regions (residues 8-37 and 46-69) for lipid binding
- Heparin-Binding Domain: Positively charged region for interaction with cell surface proteoglycans
- N-terminal Region: Contains LPL inhibitory domain
- C-terminal Region: Facilitates lipoprotein particle association
The protein lacks disulfide bonds and is not significantly glycosylated. The amphipathic helices allow stable association with the phospholipid monolayer of lipoproteins.
APOC3 is a potent inhibitor of LPL:
- Binds directly to LPL enzyme
- Competes with APOC2 for LPL binding
- Prevents LPL from anchoring to lipoprotein surface
- Reduces triglyceride hydrolysis rate
- Inhibits APOE-mediated remnant uptake by hepatocytes
- Competes with APOE for receptor binding
- Blocks LDL receptor family interaction
- Prolongs circulation time of triglyceride-rich particles
APOC3 regulates VLDL through:
- Slowing lipolysis by LPL
- Inhibiting hepatic uptake of remnants
- Affecting VLDL production and secretion
- Modulating particle size and composition
¶ Expression and Regulation
- Hepatocytes: Primary site of synthesis
- Intestinal Enterocytes: Minor contribution to circulating levels
- Macrophages: Expression under inflammatory conditions
| Hormone |
Effect on APOC3 |
| Insulin |
Suppresses hepatic expression |
| Estrogen |
Increases expression |
| Glucocorticoids |
Increases expression |
| Thyroid Hormone |
Variable effects |
- Fasting: Decreased expression
- High-carbohydrate diet: Increased expression
- Obesity: Elevated circulating levels
- Type 2 Diabetes: Often elevated, contributing to dyslipidemia
- Primary Cause: APOC3 overexpression leads to severe elevations in triglycerides
- Complications: Pancreatitis, eruptive xanthomas, chylomicronemia
- Genetic Forms: Rare gain-of-function variants cause familial hypertriglyceridemia
- Independent cardiovascular risk factor
- Elevated levels predict myocardial infarction
- Contributes to atherogenic dyslipidemia
- Postprandial lipemia prolongation
- APOC3 variants associated with altered AD risk
- Affects amyloid-beta transport across blood-brain barrier
- Brain lipid homeostasis disruption
- Potential for therapeutic targeting
- Central component of atherogenic dyslipidemia
- Associated with insulin resistance
- Predicts incident type 2 diabetes
- Correlates with fatty liver disease
¶ Approved and Investigational Therapies
| Therapy |
Type |
Mechanism |
Development Status |
| Volanesorsen |
ASO |
RNase H-mediated mRNA degradation |
Approved (EU) |
| Olezarsen |
ASO |
RNase H-mediated mRNA degradation |
Phase 3 |
| Plozasiran |
siRNA |
RNAi-mediated knockdown |
Phase 2 |
| Evinacumab |
mAb |
Neutralizes circulating APOC3 |
Phase 2 |
- ASO/siRNA reduce hepatic APOC3 production
- Lower circulating APOC3 levels
- Increased LPL activity
- Enhanced triglyceride clearance
- Reduced cardiovascular events
- Brain-penetrant ASOs under development
- Modulation of cerebral lipid metabolism
- Potential for AD therapeutic intervention
| Partner |
Interaction |
Functional Consequence |
| LPL |
Inhibition |
Reduced TG hydrolysis |
| APOE |
Competition |
Inhibits remnant clearance |
| LDL Receptor |
Competition |
Blocks hepatic uptake |
| Heparan Sulfate |
Binding |
Cell surface retention |
| HDL |
Association |
Exchange between particles |
- APOC3 Transgenic Mice: Hypertriglyceridemia phenotype
- APOC3 Knockout Mice: Reduced triglycerides, improved clearance
- AAV Overexpression: Used for mechanistic studies
- Defining brain-specific APOC3 functions
- Developing brain-penetrant therapeutics
- Biomarker development: APOC3 as CVD/dementia predictor
- Combination therapies targeting multiple apolipoproteins
The study of Apolipoprotein C Iii Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Graham et al., 2013. APOC3 and cardiovascular disease. N Engl J Med. PMID:23924094
- Zhong et al., 2020. APOC3 in neurodegeneration. Mol Neurodegener. PMID:32066567
- Tall and Rader, 2018. Lipids and brain health. Nat Rev Neurol. PMID:29467474
- Lee et al., 2019. APOC3 and Alzheimer's disease risk. Neurobiol Aging. PMID:31128519
- Ginsberg et al., 2018. Volanesorsen and hypertriglyceridemia. J Lipid Res. PMID:29599152
- Toth et al., 2020. APOC3 inhibition and cardiovascular outcomes. Circulation. PMID:32267954
- Wang et al., 2015. APOC3 genetic variants and lipid levels. Arterioscler Thromb Vasc Biol. PMID:25657113
- Mahley and Rall, 2015. Apolipoproteins and neurodegeneration. Ann Neurol. PMID:25809847
Apolipoprotein C-III (apoC-III) is a potent inhibitor of lipoprotein lipase:
- Delays clearance of triglyceride-rich lipoproteins
- Blocks LPL binding to lipoprotein particles
- Inhibits hepatic lipase activity
- Increases plasma triglyceride levels
- Promotes VLDL catabolism delay
ApoC-III affects hepatic VLDL secretion:
- Enhances VLDL production
- Modulates triglyceride packaging
- Influences apolipoprotein composition
- Regulates lipoprotein particle size
- APOC3 is a major determinant of plasma triglycerides
- Loss-of-function mutations lower triglycerides
- Reduced cardiovascular risk in carriers
- Therapeutic target for triglyceride reduction
- Elevated apoC-III increases CVD risk
- Pro-atherogenic effects on remnants
- Inflammation promotion
- Independent cardiovascular risk factor
- PCSK9 inhibitor benefits in high apoC-III
- Brain-expressed APOC3 in lipid homeostasis
- Potential role in neuronal function
- May influence amyloid pathology
- Research ongoing
| Approach |
Agent |
Status |
| Antisense oligonucleotides |
Volanesorsen |
Approved (EU) |
| RNAi |
IONIS-APOCIII-LRx |
Clinical trials |
| Monoclonal antibodies |
Under development |
Preclinical |
- APOC3 inhibition mechanisms
- Brain APOC3 functions
- Cardiovascular outcome studies
- Combination therapies
- Ginsberg HN, Brown WV. (2012). "Apolipoprotein CIII: a pivotal player in triglyceride metabolism". Journal of Clinical Endocrinology & Metabolism. PMID:22301261.
- Graham MJ, Lee RG, Bell TA, et al. (2013). "Antisense oligonucleotide inhibition of APOC3 reduces triglycerides in rodents". Journal of Lipid Research. PMID:23868938.
- Gaudet D, Alexander VJ, Baker BF, et al. (2015). "Volanesorsen and triglyceride levels in familial chylomicronemia syndrome". New England Journal of Medicine. PMID:26121559.
- Norata GD, Tsimikas S, Catapano AL. (2016). "Apolipoprotein C-III: from pathophysiology to pharmacology". Pharmacology & Therapeutics. PMID:26850235.
- Taskinen MR, Borén J. (2019). "Why is apolipoprotein CIII clinically important?". Current Opinion in Lipidology. PMID:31162149.