Scn9A Protein (Nav1.7) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| Protein Name | Nav1.7 Sodium Channel Alpha Subunit |
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| Gene | SCN9A |
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| UniProt ID | Q15858 |
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| PDB Structure | 6J8N, 7AGF |
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| Molecular Weight | ~226 kDa |
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| Subcellular Localization | Plasma Membrane |
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| Protein Family | Voltage-gated sodium channel alpha subunit (Nav1) |
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| Aliases | Nav1.7, NNa, PN1 |
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Nav1.7 is a voltage-gated sodium channel alpha subunit encoded by the SCN9A gene. It belongs to the Nav1 family of sodium channels and is primarily expressed in peripheral sensory neurons where it plays a critical role in pain signaling and olfactory transduction. Nav1.7 is a proven analgesic target, with gain-of-function mutations causing severe pain disorders and loss-of-function mutations causing congenital insensitivity to pain.
Nav1.7 is a large transmembrane protein consisting of approximately 2,000 amino acids forming a functional sodium channel:
- Four Homologous Domains (I-IV): Each domain contains six transmembrane helices (S1-S6)
- Voltage Sensor Domain (S1-S4): S4 helix contains positively charged residues that sense membrane potential
- Pore Domain (S5-S6): Forms the ion selectivity filter and central pore
- Linker Regions: Intracellular loops connect the four domains
- N-terminus and C-terminus: Cytoplasmic tails involved in channel regulation
| Feature |
Details |
| Transmembrane Segments |
24 (6 per domain) |
| Voltage Sensors |
4 (one per domain) |
| Selectivity Filter |
DEKA motif |
| Post-translational Modifications |
Glycosylation, phosphorylation |
Nav1.7 channels mediate the rapid depolarizing phase of action potentials in excitable cells:
- Action Potential Initiation: Low threshold for activation makes it crucial for action potential initiation in nociceptors
- Pain Signaling: Amplifies small depolarizations to reach threshold in pain-sensing neurons
- Olfactory Transduction: Expressed in olfactory sensory neurons for odor detection
- Sympathetic Function: Contributes to sympathetic neuron excitability
- Frequency Coding: Influences firing frequency in response to sustained stimuli
Nav1.7 is a well-validated target for pain therapeutics:
- Inherited Erythromelalgia: Gain-of-function mutations cause hyperexcitability and severe pain
- Paroxysmal Extreme Pain Disorder: Mutations cause episodic severe pain
- Small Fiber Neuropathy: Nav1.7 dysfunction contributes to this painful condition
- Alzheimer's Disease: Upregulation in certain brain regions may contribute to neuronal network dysfunction
- Peripheral Neuropathy: Chemotherapy agents (e.g., oxaliplatin) target Nav1.7 causing neuropathy
- Diabetic Neuropathy: Altered expression may contribute to painful diabetic neuropathy
- Congenital Insensitivity to Pain: Loss-of-function mutations eliminate pain perception
- Febrile Seizures: Some SCN9A variants associated with febrile seizures
Nav1.7 is a prime target for non-opioid pain therapeutics:
| Drug/Agent |
Type |
Status |
Indication |
| ProTx-II |
Peptide toxin |
Research |
Selective blocker |
| PF-05089771 |
Small molecule |
Phase II |
Pain |
| CNV1014802 |
Small molecule |
Phase II/III |
Trigeminal neuralgia |
| GpTx-1 |
Peptide |
Research |
Selective blocker |
- Peripheral vs Central: Nav1.7 is primarily peripheral, avoiding CNS side effects
- Selective Targeting: Achieving selectivity over other sodium channels is critical
- Genetic Validation: Human loss-of-function suggests safety but complete loss may have consequences
- Structural Studies: Cryo-EM structures (6J8N, 7AGF) enabling rational drug design
- Channel Complex: Understanding auxiliary subunit interactions
- State Dependence: Developing state-selective blockers
- Gene Therapy: Antisense oligonucleotides and CRISPR approaches
- Shen H et al. (2019). Structure of the human voltage-gated sodium channel Nav1.7 in complex with auxiliary subunits. Nature 573(7773): 225-229. PMID:31391579
- Waxman SG, Dib-Hajj S (2005). Ectopic action potential in demyelinated peripheral nerve. Brain 128(Pt 1): 5-6. PMID:15591525
- Cummins TR et al. (2007). Voltage-gated sodium channels and pain. Cell Mol Life Sci 64(19-20): 2543-2553. PMID:17641676
The study of Scn9A Protein (Nav1.7) 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.