GO:0034363 intermediate-density lipoprotein particle: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034363 describes the intermediate-density lipoprotein (IDL) particle, a triglyceride-rich lipoprotein of density 1.006-1.019 g/ml and diameter 25-30 nm that carries APOB100, APOE and APOCs in blood.
• IDL is generated by delipidation of very-low-density lipoprotein (VLDL) and is removed by the liver via APOE receptor binding or converted to low-density lipoprotein (LDL).
• Elevated IDL particles are associated with progression of carotid atherosclerosis in community-based cohorts.
• APOB100 is the structural backbone of IDL and related atherogenic particles, making it a biomarker and therapeutic target.
• IDL subspecies can be separated by electronegativity-based subfractionation, revealing heterogeneity relevant to cardiovascular risk.
• Studying IDL biology requires integrated cell models (knockout, knock-in, overexpression) and CRISPR screening combined with lipidomics and imaging.
Description
Intermediate-density lipoprotein (IDL) particles are triglyceride-rich lipoproteins that occupy a critical position in the lipoprotein cascade, bridging VLDL and LDL in the bloodstream. The Gene Ontology term GO:0034363 defines this particle as a cellular component with a density of 1.006-1.019 g/ml and a diameter of 25-30 nm, typically containing APOB100, APOE and APOCs. Because IDL is a direct precursor of LDL and a ligand for hepatic APOE receptors, its metabolism is central to cholesterol homeostasis and cardiovascular risk. Researchers study IDL to understand how delipidation, receptor clearance and subfraction heterogeneity contribute to atherosclerosis and related diseases. The particle is not merely a passive transport vehicle; its apolipoprotein composition determines tissue uptake and its retention in the artery wall can initiate atherogenic processes. Consequently, GO:0034363 is a meaningful annotation for projects that model lipoprotein assembly, clearance and dyslipidemia using CRISPR-edited cells and animal models.
intermediate-density lipoprotein particle At A Glance
| GO ID | GO:0034363 |
|---|---|
| GO term | intermediate-density lipoprotein particle |
| Ontology | cellular_component |
| Synonym | IDL complex; IDL particle; intermediate-density lipoprotein complex |
| Major function | Transports triglycerides and cholesterol in blood as an intermediate between VLDL and LDL; serves as a ligand for hepatic APOE receptor-mediated clearance |
| Density | 1.006-1.019 g/ml |
| Diameter | 25-30 nm |
| Typical apolipoproteins | APOB100, APOE, APOCs |
| Formation | Delipidation of VLDL particles |
| Fate | Hepatic removal via APOE receptor or conversion to LDL |
What Is GO:0034363?
GO:0034363 intermediate-density lipoprotein particle is a triglyceride-rich lipoprotein complex found in blood, defined by a density of 1.006-1.019 g/ml and a diameter of 25-30 nm. It typically contains APOB100, APOE and APOC apolipoproteins. IDL particles are formed by delipidation of VLDL particles and are either removed from blood by the liver after binding to the APOE receptor or further converted to LDL.
Why Is intermediate-density lipoprotein particle Important in Cell Biology?
IDL particles are important because they represent a metabolically active junction in lipoprotein metabolism: they are the immediate precursors of LDL and a direct ligand for hepatic clearance pathways, so their concentration and composition influence circulating cholesterol levels and cardiovascular risk. Community-based cohort data show that higher IDL particle levels associate with progression of carotid atherosclerosis, supporting IDL as a risk-relevant biomarker. Because APOB100 is the structural protein of IDL and related particles, it is a major biomarker and potential therapeutic target in cardiovascular disease. Understanding IDL biology therefore informs risk assessment, drug development and mechanistic studies of dyslipidemia.
• IDL is the direct metabolic precursor of LDL, linking triglyceride-rich lipoprotein metabolism to atherogenic cholesterol.
• IDL particles carry APOB100, APOE and APOCs, which determine receptor binding and tissue clearance.
• Elevated IDL particle levels are associated with progression of carotid atherosclerosis.
• APOB100, the core protein of IDL, is a validated biomarker and therapeutic target in cardiovascular disease.
• IDL subspecies can be resolved by electronegativity-based subfractionation, revealing risk-relevant heterogeneity.
• IDL and LDL subspecies have been linked to coronary artery disease risk in classic studies.
• IDL metabolism is a key readout for testing gene function in lipid disorders using CRISPR models.
• Studying IDL helps explain how hepatic APOE receptor clearance regulates plasma lipoprotein levels.
• IDL is relevant to dyslipidemia, metabolic syndrome and atherosclerosis research.
• IDL particle measurement can complement standard lipid panels in cardiovascular risk research.
What Happens During intermediate-density lipoprotein particle?
Formation by VLDL delipidation
In simple terms: IDL is made when VLDL loses some of its fat.
IDL particles are formed by delipidation of very-low-density lipoprotein (VLDL) particles in the bloodstream. This process removes triglycerides from VLDL, producing a smaller, denser particle that retains APOB100 and acquires or exchanges APOE and APOC apolipoproteins. The resulting IDL has a density of 1.006-1.019 g/ml and a diameter of 25-30 nm.
Circulation and apolipoprotein composition
In simple terms: IDL travels in blood carrying specific proteins on its surface.
IDL particles circulate in blood and typically contain APOB100, APOE and APOCs. APOB100 provides structural integrity and is the core apolipoprotein of IDL and LDL. APOE on the IDL surface enables binding to hepatic receptors, while APOCs modulate lipoprotein metabolism.
Hepatic clearance via APOE receptor
In simple terms: The liver removes IDL by recognizing APOE on its surface.
IDL particles are removed from blood by the liver following binding to the APOE receptor. This receptor-mediated uptake is a major route for clearing IDL and regulating plasma lipoprotein levels. Defects in this clearance pathway can lead to accumulation of IDL and related atherogenic particles.
Conversion to LDL
In simple terms: Some IDL is further processed into LDL.
IDL particles that are not cleared by the liver can be converted to low-density lipoprotein (LDL). This conversion involves further loss of triglycerides and remodeling of apolipoproteins, yielding a cholesterol-enriched particle. Because LDL is strongly linked to atherosclerosis, the IDL-to-LDL transition is a key step in cardiovascular risk.
Subfraction heterogeneity
In simple terms: IDL is not a single uniform particle; it has subtypes.
IDL particles can be separated into subfractions based on electronegativity, revealing heterogeneity that may relate to cardiovascular risk. Classic studies have also described intermediate and low-density lipoprotein subspecies in relation to coronary artery disease risk. This heterogeneity means that measuring total IDL may not capture all functionally relevant particles.
Key Genes Involved in GO:0034363 intermediate-density lipoprotein particle
The following genes and apolipoproteins are central to the structure, metabolism and clearance of the intermediate-density lipoprotein particle.
| Gene | Major Role | Research Relevance |
|---|---|---|
| APOB | Encodes APOB100, the structural apolipoprotein of IDL, VLDL and LDL | Biomarker and therapeutic target in cardiovascular disease; knockout and knock-in models for lipoprotein assembly |
| APOE | Surface apolipoprotein that mediates hepatic receptor binding and IDL clearance | Key determinant of IDL removal; knockout models show impaired clearance |
| APOC1 | APOC apolipoprotein component of IDL that modulates lipoprotein metabolism | Candidate for studies of triglyceride-rich lipoprotein remodeling |
| APOC2 | APOC apolipoprotein component of IDL; regulator of lipoprotein lipase activity | Relevant to triglyceride metabolism and IDL formation |
| APOC3 | APOC apolipoprotein component of IDL; inhibitor of lipoprotein lipase | Target for dyslipidemia research and CRISPR knockout studies |
| LDLR | Receptor that clears APOB-containing lipoproteins including LDL and contributes to IDL metabolism | Central to familial hypercholesterolemia models and lipoprotein clearance studies |
| LRP1 | Receptor involved in hepatic clearance of APOE-containing lipoproteins | Candidate for IDL clearance studies in liver cells |
| MTTP | Microsomal triglyceride transfer protein required for APOB lipidation and VLDL/IDL assembly | Knockout causes abetalipoproteinemia; useful for assembly studies |
| PCSK9 | Regulates LDLR degradation and indirectly influences IDL/LDL clearance | Therapeutic target; knockout and point-mutation models for cholesterol research |
| CETP | Cholesteryl ester transfer protein that remodels lipoproteins including IDL | Relevant to lipoprotein remodeling and cardiovascular risk studies |
| LPL | Lipoprotein lipase that hydrolyzes triglycerides in VLDL and IDL | Key enzyme for IDL formation; knockout models show severe dyslipidemia |
| APOA5 | Modulates lipoprotein lipase activity and triglyceride-rich lipoprotein metabolism | Candidate for IDL formation studies |
| ANGPTL3 | Inhibitor of lipoprotein lipase and endothelial lipase | Therapeutic target for dyslipidemia; CRISPR knockout models available |
| ANGPTL4 | Regulator of lipoprotein lipase activity | Relevant to triglyceride-rich lipoprotein processing |
| SORT1 | Sortilin, involved in hepatic VLDL secretion and lipoprotein metabolism | Candidate for IDL/VLDL secretion studies |
| ABCA1 | Cholesterol efflux transporter that influences lipoprotein profiles | Relevant to HDL and lipoprotein metabolism crosstalk |
| SCARB1 | Scavenger receptor BI, binds lipoproteins including IDL and HDL | Candidate for lipoprotein uptake studies |
| NR1H2 | LXR beta, nuclear receptor regulating lipid metabolism genes | Useful for overexpression and knockout studies of lipoprotein pathways |
How Is intermediate-density lipoprotein particle Regulated?
IDL particle metabolism is regulated at multiple levels. Lipoprotein lipase (LPL) hydrolyzes triglycerides in VLDL and IDL, and its activity is modulated by APOC2, APOC3, APOA5 and ANGPTL proteins. Hepatic clearance of IDL depends on APOE-mediated receptor binding, and receptors such as LDLR and LRP1 contribute to lipoprotein uptake. PCSK9 regulates LDLR availability and thereby indirectly influences IDL and LDL clearance. CETP remodels lipoproteins by transferring cholesteryl esters and triglycerides between particles, affecting IDL composition. Nuclear receptors such as LXRs regulate expression of genes involved in lipid metabolism, providing transcriptional control over lipoprotein production and clearance. Together, these regulatory layers determine the balance between IDL formation, clearance and conversion to LDL.
intermediate-density lipoprotein particle and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| APOB | Atherosclerosis and cardiovascular disease; APOB100 is a biomarker and therapeutic target | APOB knockout and knock-in hepatocyte models for lipoprotein assembly |
| APOE | Impaired IDL clearance and dyslipidemia | APOE knockout mice and isogenic APOE knockout cell lines |
| LDLR | Familial hypercholesterolemia and defective lipoprotein clearance | LDLR knockout and point-mutation cell models |
| PCSK9 | Hypercholesterolemia via LDLR degradation | PCSK9 overexpression and knockout cell models |
| LPL | Severe hypertriglyceridemia and impaired IDL formation | LPL knockout and point-mutation models |
Atherosclerosis and cardiovascular disease
Elevated IDL particle levels are associated with progression of carotid atherosclerosis in community-based cohorts. IDL is a direct precursor of LDL, and both IDL and LDL subspecies have been linked to coronary artery disease risk. Because IDL carries APOB100 and can be retained in the artery wall, it contributes to atherogenic processes. APOB100 is a validated biomarker and potential therapeutic target in cardiovascular disease.
Dyslipidemia and metabolic disorders
Disorders of lipoprotein metabolism can lead to accumulation of triglyceride-rich particles including IDL. Defects in LPL, APOC2, APOA5 or ANGPTL proteins impair lipolysis and increase IDL and VLDL levels. Mutations affecting MTTP cause abetalipoproteinemia, demonstrating the importance of APOB lipidation in particle assembly. PCSK9 gain-of-function variants increase LDL and are relevant to familial hypercholesterolemia.
Familial hypercholesterolemia and receptor defects
LDLR mutations cause familial hypercholesterolemia, and impaired receptor-mediated clearance affects IDL and LDL metabolism. LRP1 and APOE are also involved in hepatic clearance of APOE-containing lipoproteins, so defects in these pathways can alter IDL removal. Studying these genes in cell models helps dissect the relative contributions of each clearance route.
From intermediate-density lipoprotein particle-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does APOB loss impair IDL assembly and secretion? | APOB knockout hepatocyte cell line |
| Does APOE deficiency reduce hepatic IDL clearance? | APOE knockout cell model or mouse |
| Does a point mutation in LDLR alter IDL uptake? | LDLR point-mutation knock-in cells |
| Can tagged APOB track IDL particle trafficking? | APOB tagged knock-in cell line |
| Does PCSK9 overexpression reduce IDL clearance? | PCSK9 overexpression hepatocyte model |
| Which genes regulate IDL-to-LDL conversion? | CRISPR library screening in lipoprotein-secreting cells |
How to Study the intermediate-density lipoprotein particle Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ultracentrifugation | Lipoprotein density fractions including IDL | Isolation of IDL from plasma or cell culture media |
| Electronegativity-based subfractionation | IDL subspecies heterogeneity | Comparing IDL subfractions with main lipoprotein classes |
| Lipidomics | Triglyceride and cholesterol content of IDL | Characterizing lipoprotein composition |
| CRISPR library screening | Genes regulating IDL metabolism | Unbiased discovery of lipoprotein modulators |
| Fluorescence imaging | IDL binding, uptake and trafficking | Tracking receptor-mediated clearance in cells |
| APOB quantification | APOB100 levels as a biomarker | Cardiovascular risk assessment and target validation |
| Cohort epidemiology | Association of IDL particles with atherosclerosis progression | Population-based risk studies |
| Subspecies profiling | IDL and LDL subspecies distribution | Coronary artery disease risk research |
Lipoprotein fractionation and lipidomics
IDL particles are defined by density and size, so ultracentrifugation and size-based separation are standard methods to isolate them. Electronegativity-based subfractionation can further resolve IDL subspecies and compare them with main lipoprotein classes. Lipidomics and apolipoprotein profiling then quantify triglyceride, cholesterol and apolipoprotein content.
CRISPR screening and functional genomics
CRISPR library screening can identify genes that regulate IDL formation, clearance or conversion to LDL. Pooled screens in hepatocyte-like cells coupled with lipoprotein readouts enable unbiased discovery of modulators. Bioinformatics analysis of screen hits can map candidates to lipid metabolism pathways.
Imaging and trafficking assays
Fluorescently labeled lipoproteins or tagged apolipoproteins can be used to track IDL binding, uptake and intracellular trafficking in live cells. Imaging approaches help distinguish receptor-mediated clearance from fluid-phase uptake. Co-localization with endosomal and lysosomal markers provides mechanistic insight.
Clinical and epidemiological measurement
Community-based cohort studies measure IDL particles to assess associations with atherosclerosis progression. Classic studies have related IDL and LDL subspecies to coronary artery disease risk. These measurements support translational research linking IDL biology to patient outcomes.
How CRISPR Can Be Used to Study GO:0034363 intermediate-density lipoprotein particle
Knockout
CRISPR knockout of APOB, APOE, LDLR, PCSK9 or LPL in hepatocyte-like cells can reveal their roles in IDL assembly, clearance and conversion to LDL. Knockout models are useful for establishing causality between a candidate gene and IDL-related phenotypes. Loss-of-function screens can identify novel regulators of lipoprotein metabolism.
Point Mutation
Point-mutation knock-in models can mimic naturally occurring variants in APOB, LDLR or PCSK9 to study their effects on IDL metabolism. Such models help distinguish loss-of-function from gain-of-function mechanisms. They are valuable for testing genotype-phenotype relationships in dyslipidemia.
Knock-in
Knock-in of tagged APOB or APOE allows tracking of IDL particles and their trafficking in live cells. Reporter knock-ins can quantify promoter activity and protein localization. These models support mechanistic studies of IDL clearance and conversion.
Overexpression
Overexpression of PCSK9, APOC3 or ANGPTL3 can increase IDL and related atherogenic particles, providing models for dyslipidemia research. Overexpression studies complement knockout approaches to define directionality of effect. They are also useful for testing therapeutic targets.
How EDITGENE Supports intermediate-density lipoprotein particle Research
Researchers studying intermediate-density lipoprotein particle-related genes often need to determine whether a candidate gene is causally involved in IDL formation, clearance or conversion to LDL. EDITGENE provides CRISPR-engineered cell models and screening services that enable such causal tests in a controlled, reproducible manner.
Contact EDITGENE today to design your custom CRISPR model for intermediate-density lipoprotein particle research.
Frequently Asked Questions About intermediate-density lipoprotein particle
What is GO:0034363 intermediate-density lipoprotein particle?
GO:0034363 is a Gene Ontology cellular component term describing a triglyceride-rich lipoprotein particle of density 1.006-1.019 g/ml and diameter 25-30 nm that typically contains APOB100, APOE and APOCs.
What genes are involved in intermediate-density lipoprotein particle?
Key genes include APOB, APOE, APOC1, APOC2, APOC3, LDLR, LRP1, MTTP, PCSK9, CETP, LPL, APOA5, ANGPTL3, ANGPTL4, SORT1, ABCA1, SCARB1 and NR1H2.
How is IDL formed?
IDL is formed by delipidation of VLDL particles in the bloodstream.
What is the difference between IDL and LDL?
IDL is a triglyceride-rich precursor with density 1.006-1.019 g/ml, while LDL is a more cholesterol-enriched particle formed by further processing of IDL.
Why is IDL important in cardiovascular disease?
Elevated IDL particles are associated with progression of carotid atherosclerosis, and IDL is a direct precursor of LDL.
What apolipoproteins are on IDL?
IDL typically contains APOB100, APOE and APOCs.
How is IDL cleared from blood?
IDL is removed by the liver following binding to the APOE receptor, or converted to LDL.
Can CRISPR be used to study IDL metabolism?
Yes, CRISPR knockout, point-mutation, knock-in and overexpression models can test gene function in IDL formation, clearance and conversion.
What methods measure IDL particles?
Ultracentrifugation, electronegativity-based subfractionation, lipidomics and cohort epidemiology are used to measure IDL particles.
What diseases are linked to IDL?
IDL has been linked to atherosclerosis, dyslipidemia and familial hypercholesterolemia through genes such as APOB, APOE, LDLR and PCSK9.
Conclusion
GO:0034363 intermediate-density lipoprotein particle represents a metabolically pivotal lipoprotein that bridges VLDL and LDL and is directly relevant to cardiovascular risk. Its apolipoprotein composition, hepatic clearance via APOE receptors and conversion to LDL make it a rich target for mechanistic and translational research. CRISPR-based cell models and screening approaches now allow researchers to test causal roles of genes such as APOB, APOE, LDLR and PCSK9 in IDL biology. Continued work on IDL subfractions and clearance pathways may refine risk assessment and therapeutic strategies for atherosclerosis and dyslipidemia.
References
- 1. Feingold KR. 2022. Lipid and Lipoprotein Metabolism.. Endocrinol Metab Clin North Am 51(3):437-458 PMID: 35963623
- 2. Narang D et al.. 2026. Biochemistry, Intermediate Density Lipoprotein.. PMID: 40198056
- 3. Liu T et al.. 2023. Association between Intermediate-Density Lipoprotein Particles and the Progression of Carotid Atherosclerosis: A Community-Based Cohort Study.. J Atheroscler Thromb 30(11):1644-1660 PMID: 37045783
- 4. Bailey A et al.. 2026. Biochemistry, High Density Lipoprotein.. PMID: 31747209
- 5. Devaraj S et al.. 2026. Biochemistry, Apolipoprotein B.. PMID: 30844166
- 6. Behbodikhah J et al.. 2021. Apolipoprotein B and Cardiovascular Disease: Biomarker and Potential Therapeutic Target.. Metabolites 11(10) PMID: 34677405
- 7. Akyol O et al.. 2026. Electronegativity-based subfractionation of intermediate-density lipoproteins: Comparison with main lipoprotein classes.. Biochimie PMID: 42637209
- 8. Krauss RM. 1987. Relationship of intermediate and low-density lipoprotein subspecies to risk of coronary artery disease.. Am Heart J 113(2 Pt 2):578-82 PMID: 3544774
