Serotonin Receptor 3A Protein

Serotonin Receptor 3A Protein

Introduction

Serotonin Receptor 3A 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.

Overview

<div class="infobox infobox-protein"> [@thompson2007]
<table> [@davies1999]
<tr><th colspan="2" style="background:#4477AA; color:white; text-align:center">HTR3A</th></tr> [@machu2011]
<tr><th>Protein Name</th><td>5-Hydroxytryptamine Receptor 3A</td></tr> [@van2022]
<tr><th>Gene</th><td>[HTR3A](/genes/htr3a)</td></tr>
<tr><th>UniProt ID</th><td>[P23978](https://www.uniprot.org/uniprot/P23978)</td></tr>
<tr><th>PDB IDs</th><td>6Y0Z, 7XP3</td></tr>
<tr><th>Molecular Weight</th><td>55.0 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Plasma Membrane (Ligand-Gated Ion Channel)</td></tr>
<tr><th>Protein Family</th><td>Cys-Loop Receptor, Ion Channel</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Structure

Serotonin Receptor 3A Protein

Introduction

Serotonin Receptor 3A 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.

Overview

<div class="infobox infobox-protein"> [@thompson2007]
<table> [@davies1999]
<tr><th colspan="2" style="background:#4477AA; color:white; text-align:center">HTR3A</th></tr> [@machu2011]
<tr><th>Protein Name</th><td>5-Hydroxytryptamine Receptor 3A</td></tr> [@van2022]
<tr><th>Gene</th><td>[HTR3A](/genes/htr3a)</td></tr>
<tr><th>UniProt ID</th><td>[P23978](https://www.uniprot.org/uniprot/P23978)</td></tr>
<tr><th>PDB IDs</th><td>6Y0Z, 7XP3</td></tr>
<tr><th>Molecular Weight</th><td>55.0 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Plasma Membrane (Ligand-Gated Ion Channel)</td></tr>
<tr><th>Protein Family</th><td>Cys-Loop Receptor, Ion Channel</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Structure

The HTR3A protein forms a pentameric ligand-gated ion channel, a member of the Cys-loop receptor superfamily. Each subunit consists of an extracellular N-terminal domain containing the characteristic Cys-loop motif, followed by four transmembrane domains (TM1-TM4). The ion channel pore is formed by the TM2 helices of each subunit. The receptor can form as homomeric HTR3A assemblies or heteromeric assemblies with HTR3B subunits, which modify channel properties. The extracellular domain contains the binding site for serotonin and allosteric modulators.

Normal Function

The 5-HT3 receptor is the only ionotropic serotonin receptor (1-7). Unlike other serotonin receptors that are GPCRs, HTR3A functions as a cation channel that conducts Na+, K+, and Ca2+ ions upon serotonin binding. Activation causes rapid depolarization and neuronal excitation. In the brain, HTR3A is expressed in areas involved in emesis, pain perception, mood, and cognition. It plays roles in:

• Fast synaptic transmission in the hippocampus and cortex
• Modulation of dopamine release in the nucleus accumbens
• Regulation of gastrointestinal motility (peripheral receptors)
• Anxiety and nausea signaling

Expression Pattern

5-HT3A receptor expression in the brain:

• [Hippocampus](/brain-regions/hippocampus): High expression in CA1 pyramidal [neurons](/entities/neurons) and interneurons
• [Cortex](/brain-regions/cortex): Layer-specific expression in pyramidal neurons and GABAergic interneurons
• Amygdala: Expression in central and basolateral nuclei
• Striatum: Moderate expression in medium spiny neurons
• Brainstem: Expression in area postrema (chemoreceptor trigger zone)
• Enteric Nervous System: High expression in submucosal and myenteric plexus

Role in Neurodegeneration

HTR3A is implicated in neurodegenerative diseases through various mechanisms:

Alzheimer's Disease

• Modulates [amyloid-beta](/proteins/amyloid-beta) induced neuronal dysfunction
• Affects calcium homeostasis and excitotoxicity
• Alters neurotransmitter release including [acetylcholine](/entities/acetylcholine)

Parkinson's Disease

• Influences dopaminergic neuron function
• May affect levodopa-induced dyskinesias
• Modulates non-motor symptoms including nausea

ALS

• Altered expression in motor neurons
• Affects excitatory neurotransmission
• May contribute to excitotoxicity

Therapeutic Implications

Drug Targets

• Ondansetron, Granisetron: Antiemetic agents blocking HTR3A
• Potential Applications: Cognitive enhancement, pain management, mood disorders

Clinical Considerations

• Peripheral HTR3 blockade handles nausea without CNS side effects
• CNS-penetrant agonists may have neuropsychiatric applications
• Combination with other neurotransmitter modulators shows promise

Research Directions

Background

The study of Serotonin Receptor 3A 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.

See Also

• Serotonin Receptor 3A Gene - Gene page for HTR3A
• Serotonin Receptors - Category of serotonin receptors
• [Parkinson's Disease](/diseases/parkinsons- [Alzheimer's Disease](/diseases/alzheimers-disease)isease
• [Alzheimer's Disease](/diseases/alzheimers-disease) Alzheimer's disease
• Ion Channels - Ion channel category
• Serotonin Signaling - Serotonin signaling pathway

External Links

• [UniProt: P46098](https://www.uniprot.org/uniprot/P46098) - HTR3A protein database entry
• [IUPHAR/BPS Guide: 5-HT3](https://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=269) - HTR3A receptor pharmacology
• [NCBI Gene: 3359](https://www.ncbi.nlm.nih.gov/gene/3359) - HTR3A gene database

References