GO:2001142 nicotinate transport: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:2001142 nicotinate transport describes the directed movement of nicotinate (the anion of niacin, vitamin B3) into, out of, or within cells via transporters or pores.
• Nicotinate is a precursor for NAD+ biosynthesis and also acts as an agonist of the GPR109A receptor, linking transport to inflammation and carcinogenesis.
• Key transporters include SLC5A8 (SMCT1), which mediates Na+-dependent nicotinate uptake in the intestine and kidney, and additional kinetically distinct Na+-dependent systems in the small intestine.
• Nicotinate transport is relevant to drug absorption, chronic kidney disease, and metabolic disorders.
• Experimental models for studying nicotinate transport include knockout mice, point mutations in transporter genes, and overexpression systems.
• CRISPR-based editing enables precise interrogation of nicotinate transporter function in health and disease.
Description
Nicotinate, also known as niacin or vitamin B3, is an essential micronutrient that serves as a precursor for the coenzymes NAD+ and NADP+ and as a ligand for the G protein-coupled receptor GPR109A. The directed movement of nicotinate across cellular membranes is fundamental to its bioavailability and physiological actions. GO:2001142 nicotinate transport is the biological process that encompasses this movement, which is mediated by specific transporter proteins. Understanding nicotinate transport is critical for elucidating how cells acquire this vitamin, how it influences metabolic and immune pathways, and how its dysregulation contributes to disease. Research into nicotinate transport has identified multiple transport systems, including the sodium-coupled monocarboxylate transporter SLC5A8 (SMCT1) and other Na+-dependent carriers in the intestine. These transporters are potential targets for modulating nicotinate levels in conditions such as chronic kidney disease and inflammatory disorders. This article provides a comprehensive overview of the molecular mechanisms, key genes, and experimental approaches for studying nicotinate transport, based on authoritative QuickGO annotations and published literature.
nicotinate transport At A Glance
| GO ID | GO:2001142 |
|---|---|
| GO term | nicotinate transport |
| Ontology | biological_process |
| Synonym | none |
| Major function | Mediates the directed movement of nicotinate across cellular membranes via transporters or pores |
| Related transporters | SLC5A8 (SMCT1), additional Na+-dependent carriers |
| Physiological relevance | Nicotinate uptake for NAD+ synthesis and GPR109A signaling |
| Disease associations | Inflammatory bowel disease, chronic kidney disease, metabolic disorders |
What Is GO:2001142?
GO:2001142 nicotinate transport is defined as the directed movement of a nicotinate anion into, out of, or within a cell, or between cells, by means of some agent such as a transporter or pore. This process is essential for the cellular uptake and distribution of nicotinate, a key form of vitamin B3, and is mediated by specific membrane transport proteins that facilitate its passage across lipid bilayers.
Why Is nicotinate transport Important in Cell Biology?
Nicotinate transport is vital because nicotinate is a precursor for NAD+ and a ligand for GPR109A, influencing energy metabolism, immune regulation, and cell survival. Defects in transport can lead to altered nicotinate bioavailability, impacting NAD+ homeostasis and contributing to diseases such as pellagra, chronic kidney disease, and inflammation-driven carcinogenesis. Understanding the transporters and regulatory mechanisms of nicotinate transport can inform nutritional strategies and drug development.
• Nicotinate is a precursor for NAD+ and NADP+, essential coenzymes in redox reactions and cellular metabolism.
• Transport of nicotinate is required for its intestinal absorption and renal reabsorption.
• GPR109A, activated by nicotinate, suppresses colonic inflammation and carcinogenesis.
• Nicotinate transport influences drug pharmacokinetics, as SLC5A8 also transports structurally related compounds.
• Dysregulated nicotinate transport may contribute to chronic kidney disease-mineral and bone disorder (CKD-MBD).
• Genetic variations in nicotinate transporters could affect individual responses to niacin therapy.
• Studying nicotinate transport aids in understanding vitamin B3 deficiency and toxicity.
• Transporters like SLC5A8 are tumor suppressors, linking nicotinate transport to cancer biology.
• Nicotinate transport is a model for studying sodium-coupled transport mechanisms.
• CRISPR screens can identify novel regulators of nicotinate transport.
What Happens During nicotinate transport?
Substrate recognition and binding
In simple terms: The transporter protein recognizes and binds nicotinate on one side of the membrane.
Nicotinate transport begins with the specific binding of the nicotinate anion to a transporter protein embedded in the cell membrane. For example, SLC5A8 (SMCT1) binds nicotinate in a sodium-dependent manner, with structural determinants that discriminate nicotinate from other monocarboxylates. Other Na+-dependent systems in the rat small intestine exhibit distinct kinetic properties for nicotinate uptake, suggesting multiple binding sites or transporters.
Translocation across the membrane
In simple terms: The transporter changes shape to move nicotinate across the cell membrane.
After binding, the transporter undergoes conformational changes that translocate nicotinate from the extracellular to the intracellular space (or vice versa). This process is often coupled to the sodium gradient, as seen with SLC5A8, which uses the inward sodium gradient to drive nicotinate uptake. The kinetics of this step can vary among different transport systems, as demonstrated by two kinetically distinct Na+-dependent carriers in the rat small intestine.
Release and intracellular availability
In simple terms: Nicotinate is released inside the cell, where it can be used for NAD+ synthesis or other functions.
Once inside the cell, nicotinate is released from the transporter and becomes available for metabolic pathways, including the Preiss-Handler pathway for NAD+ biosynthesis. It can also bind to and activate GPR109A if present on the cell surface, but intracellular nicotinate primarily serves as a substrate for NAD+ synthesis.
Regulation of transporter activity
In simple terms: The activity of nicotinate transporters can be turned up or down by cellular signals.
Transporter activity is regulated at multiple levels, including gene expression, membrane trafficking, and post-translational modifications. For instance, SLC5A8 expression is silenced in some cancers, affecting nicotinate transport. Additionally, the sodium gradient maintained by Na+/K+-ATPase is essential for Na+-coupled nicotinate transport, linking transport to cellular energy status.
Key Genes Involved in GO:2001142 nicotinate transport
The following genes encode proteins that mediate or regulate nicotinate transport, as supported by published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC5A8 | Na+-coupled transporter for nicotinate and other monocarboxylates | Mediates intestinal and renal nicotinate uptake; tumor suppressor |
| SLC22A13 | Organic anion transporter | Potential nicotinate transport in kidney |
| SLC22A6 | Organic anion transporter | Urate and nicotinate transport |
| SLC22A8 | Organic anion transporter | Urate and nicotinate transport |
| GPR109A | Receptor for nicotinate and butyrate | Mediates anti-inflammatory effects of nicotinate |
| NADSYN1 | NAD+ synthetase | Downstream enzyme utilizing transported nicotinate |
| NMNAT1 | Nicotinamide mononucleotide adenylyltransferase | NAD+ biosynthesis from nicotinate |
| QPRT | Quinolinate phosphoribosyltransferase | NAD+ biosynthesis |
| SLC5A12 | Na+-coupled monocarboxylate transporter | Potential nicotinate transport |
| SLC16A1 | Monocarboxylate transporter | Potential nicotinate transport |
| SLC16A7 | Monocarboxylate transporter | Potential nicotinate transport |
| SLC22A2 | Organic cation transporter | Potential nicotinate transport |
| SLC22A4 | Organic cation/carnitine transporter | Potential nicotinate transport |
| SLC22A5 | Organic cation/carnitine transporter | Potential nicotinate transport |
| SLC7A5 | L-type amino acid transporter | Potential nicotinate transport |
| SLC7A8 | L-type amino acid transporter | Potential nicotinate transport |
| SLC3A2 | Amino acid transporter heavy chain | Potential nicotinate transport |
How Is nicotinate transport Regulated?
Nicotinate transport is regulated by the availability of sodium ions, as many transporters are Na+-coupled. The expression of SLC5A8 is subject to epigenetic silencing in cancer, which can reduce nicotinate uptake. Hormonal and metabolic signals may also influence transporter activity, but specific pathways remain to be fully elucidated.
nicotinate transport and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC5A8 | Colon cancer, inflammatory bowel disease | Knockout mice, overexpression in cell lines |
| GPR109A | Colitis-associated cancer | Knockout mice |
| SLC22A13 | Chronic kidney disease | Knockout rats, renal cell models |
| SLC22A6 | Hyperuricemia, gout | Knockout mice |
| SLC22A8 | Uremic toxins | Knockout mice |
Nicotinate transport in inflammation and cancer
Nicotinate activates GPR109A, which suppresses colonic inflammation and carcinogenesis. Transport of nicotinate into cells is required for its intracellular conversion to NAD+, but its extracellular actions on GPR109A depend on availability. Reduced expression of the transporter SLC5A8, a tumor suppressor, may impair nicotinate uptake and contribute to cancer progression.
Nicotinate transport in chronic kidney disease
Niacin (nicotinate) treatment is used to manage dyslipidemia in chronic kidney disease, but its efficacy is limited. Transporters in the kidney, such as SLC22A13 and SLC22A6, mediate nicotinate reabsorption and secretion, influencing its pharmacokinetics. Understanding these transporters may improve therapeutic strategies for CKD-MBD.
Nicotinate transport in metabolic and nutritional disorders
Nicotinate is a form of vitamin B3, and its transport is essential for preventing pellagra. Defects in intestinal nicotinate uptake, mediated by SLC5A8 and other Na+-dependent carriers, could lead to deficiency. Conversely, excessive transport may contribute to niacin toxicity.
From nicotinate transport-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does SLC5A8 mediate nicotinate transport in vivo? | SLC5A8 knockout mouse |
| What is the role of GPR109A in nicotinate sensing? | GPR109A knockout mouse |
| How does a point mutation in SLC5A8 affect transport kinetics? | Point-mutation knock-in cell lines |
| Can overexpression of SLC5A8 enhance nicotinate uptake? | SLC5A8 overexpression in HEK293 cells |
| What are the regulatory elements of SLC5A8? | CRISPR interference (CRISPRi) screens |
| Does nicotinate transport affect NAD+ levels? | Metabolomics in knockout models |
How to Study the nicotinate transport Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled uptake assay | Transport rate and kinetics | Characterizing SLC5A8 function |
| Two-electrode voltage clamp | Na+-coupled currents | Electrogenic transport |
| RNA-seq | Transporter gene expression | Tissue-specific expression |
| CRISPR knockout screen | Genes required for transport | Identifying novel regulators |
| Metabolomics | Intracellular NAD+ levels | Functional impact of transport |
| Immunofluorescence | Transporter localization | Membrane trafficking |
| Site-directed mutagenesis | Key residues for transport | Structure-function analysis |
| Pharmacokinetics | Nicotinate absorption in vivo | Drug transport studies |
Transport assays
Radiolabeled or fluorescent nicotinate uptake assays in cell lines or Xenopus oocytes expressing candidate transporters are used to measure transport activity and kinetics.
Electrophysiology
Two-electrode voltage clamp in oocytes can measure Na+-coupled currents induced by nicotinate, providing real-time transport activity.
Gene expression analysis
RNA-seq and qPCR can quantify transporter mRNA levels in tissues or cells under different conditions.
CRISPR screens
Genome-wide CRISPR knockout or activation screens can identify genes that regulate nicotinate transport or sensitivity.
How CRISPR Can Be Used to Study GO:2001142 nicotinate transport
Knockout
CRISPR knockout of SLC5A8 or other candidate transporters in cell lines or mice can abolish nicotinate transport, revealing their essential role.
Point Mutation
Introducing point mutations in transporter genes via CRISPR can dissect the contribution of specific amino acids to substrate binding and translocation.
Knock-in
Knock-in of tagged transporters (e.g., GFP-SLC5A8) allows visualization and biochemical isolation of the transport complex.
Overexpression
CRISPR activation (CRISPRa) or cDNA overexpression can increase transporter levels to study enhanced nicotinate uptake and downstream effects.
How EDITGENE Supports nicotinate transport Research
Researchers studying nicotinate transport-related genes often need to determine whether a candidate gene is causally involved in nicotinate uptake, metabolism, or downstream signaling. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this research, from generating knockout models to performing high-throughput screens.
Contact EDITGENE today to design your custom CRISPR model for nicotinate transport research.
Frequently Asked Questions About nicotinate transport
What is GO:2001142 nicotinate transport?
GO:2001142 is a Gene Ontology biological process term that describes the directed movement of nicotinate into, out of, or within a cell via transporters or pores.
What genes are involved in nicotinate transport?
Key genes include SLC5A8 (SMCT1), which encodes a Na+-coupled nicotinate transporter, and other SLC family members such as SLC22A13 and SLC22A6.
How is nicotinate transported into cells?
Nicotinate is transported by specific carrier proteins, often coupled to sodium ions, such as SLC5A8, which uses the sodium gradient to drive uptake.
What is the role of SLC5A8 in nicotinate transport?
SLC5A8 mediates Na+-dependent nicotinate uptake in the intestine and kidney and is also a tumor suppressor.
Is nicotinate transport linked to cancer?
Yes, the transporter SLC5A8 is silenced in some cancers, and nicotinate activation of GPR109A suppresses colonic inflammation and carcinogenesis.
How can I study nicotinate transport using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression models can be used to dissect the function of transporters like SLC5A8.
What diseases are associated with defective nicotinate transport?
Defective transport may contribute to pellagra, chronic kidney disease, and inflammatory bowel disease.
What are the methods to measure nicotinate transport?
Radiolabeled uptake assays, electrophysiology, and metabolomics are commonly used to measure transport activity.
Does nicotinate transport require sodium?
Many nicotinate transporters, such as SLC5A8, are Na+-dependent, but other systems may be sodium-independent.
What is the difference between nicotinate and nicotinamide transport?
Nicotinate and nicotinamide are both forms of vitamin B3 but are transported by distinct mechanisms; this article focuses on nicotinate transport (GO:2001142).
Conclusion
GO:2001142 nicotinate transport is a critical biological process that governs the cellular uptake and distribution of nicotinate, a key precursor for NAD+ and a ligand for GPR109A. The transporters involved, such as SLC5A8, are linked to inflammation, cancer, and kidney disease, making them attractive targets for therapeutic intervention. Continued research using CRISPR-based models and advanced screening technologies will further elucidate the regulatory networks and disease relevance of nicotinate transport.
References
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- 3. Henderson LM. 1983. Niacin.. Annu Rev Nutr 3:289-307 PMID: 6357238
- 4. Camargo SMR et al.. 2020. ACE2 and gut amino acid transport.. Clin Sci (Lond) 134(21):2823-2833 PMID: 33140827
- 6. Gopal E et al.. 2007. Transport of nicotinate and structurally related compounds by human SMCT1 (SLC5A8) and its relevance to drug transport in the mammalian intestinal tract.. Pharm Res 24(3):575-84 PMID: 17245649
- 7. Drüeke TB et al.. 2018. Lowering Expectations with Niacin Treatment for CKD-MBD.. Clin J Am Soc Nephrol 13(1):6-8 PMID: 29208625
- 8. Ohkubo M et al.. 2012. Nicotinate uptake by two kinetically distinct Na÷-dependent carrier-mediated transport systems in the rat small intestine.. Drug Metab Pharmacokinet 27(2):255-62 PMID: 22123132
