Recombinant Pongo pygmaeus 5-hydroxytryptamine receptor 2A (HTR2A)
Description
Introduction to Recombinant Pongo pygmaeus 5-hydroxytryptamine receptor 2A (HTR2A)
Recombinant Pongo pygmaeus 5-hydroxytryptamine receptor 2A (HTR2A) is a laboratory-produced protein that replicates the native serotonin 2A receptor found in Bornean orangutans. This receptor belongs to the broader family of 5-HT2 receptors, which are G-protein coupled receptors (GPCRs) involved in serotonin signaling pathways . The recombinant protein may be produced as a complete sequence or as partial fragments, depending on the specific research requirements and production methodologies .
The significance of studying the orangutan variant of HTR2A lies in its evolutionary proximity to humans, offering insights into the conservation and divergence of serotonergic systems across primate lineages. As a research tool, this recombinant protein enables investigations into receptor binding, signaling mechanisms, and pharmacological responses without the need for direct orangutan tissue sampling .
Signaling Cascade
The HTR2A receptor functions primarily through the Gαq signal transduction pathway. When activated by an agonist, the Gαq and β-γ subunits dissociate to initiate downstream effector pathways. The Gαq subunit stimulates phospholipase C (PLC) activity, which subsequently promotes the release of diacylglycerol (DAG) and inositol triphosphate . This cascade ultimately results in increased intracellular calcium levels and activation of protein kinase C (PKC).
Recent research has demonstrated that HTR2A activation is also associated with Rho signaling, which plays a crucial role in cell-matrix adhesion and cytoskeletal organization . This mechanism may have significant implications for neural circuit formation and maintenance, particularly in primates.
Interaction with Neurotransmitter Systems
Interestingly, studies with recombinant HTR2A receptors have revealed direct interactions between serotonin and dopamine receptor systems. Research has shown that dopamine can act as a partial-efficacy agonist on 5-HT2A receptors, inducing receptor internalization, albeit at higher concentrations than serotonin . This interaction between neurotransmitter systems may have clinical relevance to conditions such as anxiety, depression, and schizophrenia .
Evolutionary Conservation of HTR2A
The HTR2A receptor demonstrates significant evolutionary conservation across primate species. Haplotype structure analysis has revealed important insights into the divergence patterns at HTR2A between humans and chimpanzees . Interestingly, both human and chimpanzee lineages appear to have independently developed similar mutations at the -1438 upstream promoter site, suggesting convergent evolution or similar selective pressures .
Table 1: Comparative Features of HTR2A Across Species
| Species | Amino Acid Length | UniProt ID | Notable Variants |
|---|---|---|---|
| Pongo pygmaeus (Bornean orangutan) | 471 | Q5R4Q6 | -1438 promoter region |
| Homo sapiens (Human) | 471 | P28223 | -1438A/102T haplotype |
| Rattus norvegicus (Rat) | Varies by isoform | P14842 | Expression in mammalian cells |
| Pan troglodytes (Chimpanzee) | 471 | Multiple variants | Similar -1438 mutation to humans |
The -1438A and 102T alleles in humans have been associated with a 10%-20% increased brain and central nervous system serotonin receptor expression , highlighting the functional significance of genetic variations in this receptor.
Recombinant Protein Characteristics
Commercially available Recombinant Pongo pygmaeus HTR2A proteins are typically produced in mammalian cell expression systems to ensure proper post-translational modifications and protein folding. The recombinant proteins may include affinity tags, such as His-tags, to facilitate purification and downstream applications .
Table 2: Technical Specifications of Recombinant Pongo pygmaeus HTR2A
| Parameter | Specification | Notes |
|---|---|---|
| Form | Liquid or lyophilized powder | Dependent on manufacturer |
| Tag Type | Often His-tag | Determined during production process |
| Expression System | Mammalian cells | For proper protein folding |
| Storage Buffer | Tris-based buffer, 50% glycerol | Optimized for stability |
| Purity | >80% | Analyzed by SDS-PAGE |
| Storage Conditions | -20°C (long term), 4°C (working aliquots) | Avoid repeated freeze-thaw cycles |
| Expression Region | 1-471 amino acids | Full-length protein |
Similar production methods are employed for rat HTR2A, which is also expressed in mammalian cells with comparable purity specifications and storage requirements .
Cell-Matrix Adhesion Studies
Recent research has uncovered a novel role for 5-HT2A receptors in cell-matrix adhesion. Studies using HEK293 cells demonstrated that expression and stimulation of human or rat 5-HT2A receptors by agonists such as serotonin led to significant increases in adhesion . This function was mediated through downstream PKC and Rho signaling pathways.
The recombinant Pongo pygmaeus HTR2A provides a valuable tool for comparative studies investigating whether this adhesion property is conserved across primate species. Such research could have implications for understanding neural circuit formation in evolutionary contexts.
Pharmacological Research
The availability of recombinant HTR2A from Pongo pygmaeus enables comparative pharmacological studies between human and non-human primate serotonin receptors. Research has shown that agonists such as serotonin and 2,5-dimethoxy-4-iodoamphetamine (DOI) can stimulate the receptor, while antipsychotics including risperidone, olanzapine, and chlorpromazine act as inhibitors .
These studies are particularly relevant given the role of 5-HT2A receptors in various psychiatric conditions. Suicidal and depressed patients have been found to have higher 5-HT2A receptor densities than normal patients, suggesting that post-synaptic 5-HT2A overdensity may be involved in the pathogenesis of depression .
Evolutionary Insights and Clinical Applications
The study of Recombinant Pongo pygmaeus HTR2A offers promising avenues for understanding the evolutionary aspects of serotonergic systems. Future research might focus on comparing functional responses between orangutan and human HTR2A variants to elucidate how receptor function has evolved across primate lineages.
Additionally, understanding the genetic variations in HTR2A could yield insights into psychiatric disorders. Polymorphisms at HTR2A have been associated with variations in cortisol response to stressors and increased risk for depression and other psychiatric disorders . The orangutan HTR2A offers a comparative model to study these relationships in an evolutionary context.
Receptor Internalization and Trafficking
Further investigation into the mechanisms of HTR2A receptor internalization and recycling across species could provide valuable insights into receptor regulation. Studies with human HTR2A have shown that dopamine-internalized receptors recycle to the surface at rates similar to those of serotonin-internalized receptors . Comparative studies with Pongo pygmaeus HTR2A could reveal whether these trafficking mechanisms are evolutionarily conserved or show species-specific variations.
Product Specs
Note: While we prioritize shipping the format currently in stock, please specify your preferred format in order notes for customized preparation.
Note: All proteins are shipped with standard blue ice packs unless dry ice shipping is specifically requested and pre-arranged. Additional fees apply for dry ice shipping.
The tag type is determined during production. If a specific tag type is required, please inform us, and we will prioritize its development.
Target Background
The 5-hydroxytryptamine receptor 2A (HTR2A) is a G-protein coupled receptor that binds serotonin. It also acts as a receptor for various drugs and psychoactive substances, including mescaline, psilocybin, DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane), and LSD (lysergic acid diethylamide). Ligand binding induces a conformational change, initiating signaling through guanine nucleotide-binding proteins (G proteins) and modulating downstream effector activity. Beta-arrestin family members inhibit G protein signaling and mediate alternative signaling pathways. Signaling activates phospholipase C and a phosphatidylinositol-calcium second messenger system, impacting phosphatidylinositol 3-kinase activity and intracellular Ca2+ release. HTR2A influences neural activity, perception, cognition, and mood, playing a crucial role in behavioral regulation, including responses to anxiety and psychoactive substances. It also contributes to intestinal smooth muscle contraction and may participate in arterial vasoconstriction.
UniGene: Pab.1057
Q&A
What is Recombinant Pongo pygmaeus HTR2A and how does it differ from human HTR2A?
Recombinant Pongo pygmaeus HTR2A is a laboratory-produced protein representing the 5-hydroxytryptamine (serotonin) 2A receptor found in Bornean orangutans. This receptor belongs to the G protein-coupled receptor superfamily and is critically involved in serotonergic neurotransmission . The recombinant form typically includes the 471 amino acid sequence with potential modifications such as fusion tags to facilitate purification and experimental applications .
The key differences between orangutan and human HTR2A involve subtle amino acid variations while maintaining the essential functional domains critical for serotonin binding and signal transduction. While highly homologous, these differences can be important when using the protein as a model for human receptor pharmacology, particularly when studying drug interactions or receptor-ligand binding kinetics. Researchers often use recombinant Pongo pygmaeus HTR2A as a comparative model to understand conserved functional mechanisms of serotonin receptors across primates .
What methodological approaches are available for studying HTR2A signaling pathways?
Several methodological approaches have been established for studying HTR2A signaling:
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IP1 Accumulation Assays: Homogenous-time resolved fluorescence (HTRF) methodologies can measure inositol monophosphate (IP1) levels in brain homogenates as a downstream metabolite of Gq protein-dependent signaling pathways, which is particularly valuable for ex vivo studies .
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Genetic Modification Approaches: Comparing signaling responses between wild-type and 5-HT2AR-knockout animals can establish signaling specificity and receptor-dependent effects .
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Scaffold Protein Interaction Assays: Co-immunoprecipitation and proximity ligation assays can identify interactions between HTR2A and scaffold proteins like PSD95, arrestin, and caveolin that regulate receptor trafficking and signaling .
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Receptor Trafficking Studies: Fluorescent-tagged receptors combined with live-cell imaging enable real-time visualization of receptor internalization, recycling, and membrane localization dynamics .
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Ligand-Binding Studies: Displacement assays using labeled ligands can characterize binding profiles and pharmacological properties of different agonists and antagonists .
These methods can be applied to heterologous expression systems, primary neuronal cultures, or brain tissue homogenates depending on the specific research question.
How do genetic polymorphisms in HTR2A influence experimental design and data interpretation?
Genetic polymorphisms in HTR2A can significantly impact experimental outcomes, requiring careful consideration in research design and interpretation. Several key polymorphisms have been identified and characterized:
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rs6313 (102T/C) and rs6311 (-1438A/G): These common polymorphisms have been associated with substance use disorders and psychiatric conditions, potentially influencing receptor expression levels and function .
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Haplotype Considerations: In non-human primates, multiple SNPs in HTR2A can be manually phased into haplotypes that correlate with behavioral and physiological phenotypes .
When designing experiments with HTR2A, researchers should:
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Genotype experimental subjects (human or animal) for relevant HTR2A polymorphisms
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Include genotype as a variable in statistical analyses
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Consider potential interactions between genotype and experimental manipulations
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Interpret findings in the context of genetic background
This is especially critical in translational research where genetic variability may explain differential responses to serotonergic drugs or interventions. For animal models, genetic background should be consistent or systematically varied to avoid confounding experimental results .
What mechanisms differentiate psychedelic from non-psychedelic 5-HT2AR agonist responses?
The molecular distinction between psychedelic and non-psychedelic 5-HT2AR agonists remains an active area of investigation. Research comparing compounds like DOI (psychedelic) and 5-HTP (non-psychedelic) has revealed important mechanistic differences:
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Signaling Pathway Engagement: While both types of compounds bind to HTR2A, they appear to engage different downstream signaling cascades. For example, research using IP1 accumulation assays in mouse frontal cortex shows that DOI produces robust increases in IP1 levels while 5-HTP, despite inducing head-twitch response (HTR) behavioral effects, does not significantly increase IP1 signal .
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β-arrestin Recruitment Patterns: Evidence suggests that psychedelic and non-psychedelic agonists elicit distinct patterns of β-arrestin recruitment. Schmid et al. demonstrated that DOI and 5-HTP induce different signal transduction and trafficking patterns of 5-HT2A receptors in a β-arrestin 2-dependent manner both in vivo and in vitro .
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Regional Specificity: Psychedelic agonists show distinct regional activation patterns, with particularly robust effects in the frontal cortex compared to other brain regions like the striatum and cerebellum .
Importantly, behavioral assays like the head-twitch response do not always correlate with molecular measures of receptor activation, suggesting complex relationships between receptor engagement and behavioral outcomes. This discrepancy provides a valuable experimental window for investigating functional selectivity among different 5-HT2AR agonists .
How can researchers effectively correlate molecular HTR2A signaling with behavioral phenotypes?
Establishing reliable correlations between molecular HTR2A signaling events and behavioral outcomes requires integrated experimental approaches:
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Within-Subject Designs: Conduct behavioral assays followed by immediate tissue collection for molecular analysis in the same subjects. For example, researchers have correlated head-twitch response (HTR) counts with IP1 levels in the frontal cortex within individual animals to establish dose-response relationships for 5-HT2AR agonists .
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Dose-Response Curves: Establish complete dose-response relationships for both molecular (e.g., IP1 accumulation) and behavioral (e.g., HTR) outcomes to identify potential disconnects between receptor occupancy, signaling activation, and behavioral effects .
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Genetic Approaches: Utilize HTR2A polymorphisms or genetic knockout models to link specific receptor variants to both signaling alterations and behavioral phenotypes. Studies have demonstrated associations between HTR2A variants and social attention in rhesus macaques and perspective-taking abilities in humans .
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Pharmacological Dissection: Compare structurally diverse ligands that produce similar behavioral effects but potentially through different signaling mechanisms. For instance, comparison of DOI and 5-HTP reveals that behaviorally active compounds may differ substantially in their ability to induce IP1 accumulation .
A combined molecular-behavioral approach requires careful timing of tissue collection relative to behavioral testing and consideration of pharmacokinetic factors that may influence the temporal relationship between receptor activation and behavioral manifestations.
What PCR protocols are recommended for genotyping HTR2A polymorphisms?
Effective genotyping of HTR2A polymorphisms requires optimized PCR protocols. Based on published methodologies, the following approaches are recommended:
