NaV1.7 Antibody, Toxin & Small-Molecule Blocker: Three Ways to Interrogate One Ion Channel

An NaV1.7 antibody tells you the channel is present; a peptide toxin tells you what it does; a small-molecule blocker tells you what happens without it. No single reagent is clean on its own — each has a characteristic failure mode. The Alomone Labs range on BioHippo is one of the few places you can run all three orthogonal tools against the same ion-channel target and let them check each other. This note walks through that logic at NaV1.7 (SCN9A), then shows the same three-arm pattern at KV1.3 and CaV2.2.

Why one sodium channel gets this much attention

Voltage-gated sodium channels open in response to membrane depolarization and let Na⁺ flow into the cell. That inward current is what makes an action potential rise. Nine α-subunit isoforms have been cloned — NaV1.1 through NaV1.9 — and they are not interchangeable: each has its own tissue distribution, gating kinetics, and pharmacology.

NaV1.7, encoded by SCN9A, sits mostly in peripheral sensory and sympathetic neurons — dorsal root ganglia, trigeminal ganglia, olfactory sensory neurons. Its defining property is slow closed-state inactivation, which lets it respond to small, slow depolarizations that other NaV isoforms ignore. Functionally it behaves as a threshold amplifier: it boosts subthreshold stimuli toward the point where NaV1.8 and other isoforms fire the full action potential (Catterall et al., Pharmacol Rev 2005).

The genetics made it a drug target

NaV1.7 is unusual among ion channels in that human genetics point at it from both directions. Loss-of-function SCN9A mutations cause congenital insensitivity to pain — individuals who are otherwise neurologically intact but cannot feel pain, though they do lose the sense of smell (Cox et al., Nature 2006). Gain-of-function mutations cause inherited pain disorders including erythromelalgia and paroxysmal extreme pain disorder (Dib-Hajj et al., Nat Rev Neurosci 2013). A single gene, two opposite phenotypes, both confined largely to nociception.

That is why NaV1.7 became one of the most pursued analgesic targets in the field — and why the practical research problem is isoform selectivity. NaV1.7 shares high sequence identity with NaV1.5 (cardiac muscle) and NaV1.4 (skeletal muscle). The tissues are the reason selectivity is not a technicality: a compound or antibody that cannot distinguish NaV1.7 from NaV1.5 is reading the heart along with the nociceptor.

The NaV isoform landscape

Why the TTX column matters. Tetrodotoxin is the classic NaV blocker, and BioHippo stocks it (Tetrodotoxin, citrate free). But TTX cannot isolate NaV1.7 — it blocks six of the nine isoforms indiscriminately. Selectivity has to come from somewhere else. That is the problem the three arms below solve.

Arm 1 — NaV1.7 antibodies: is the channel there, and where?

An NaV1.7 antibody answers the detection question — presence, abundance, and localization. The critical choice is the epitope: intracellular versus extracellular. BioHippo carries five Alomone SCN9A antibody formats.

The intracellular/extracellular split is the point. ASC-008 targets an intracellular loop: it needs permeabilization and it reports total channel protein. ASC-027 and ASC-029 target extracellular epitopes, so they label surface channel on intact live cells. Trafficking questions require the second kind; abundance questions are answered by the first. A channel can be abundant in lysate and absent from the membrane, and only one of these antibodies will tell you.

Host is not reactivity. "Guinea pig Anti-NaV1.7" means the antibody was raised in a guinea pig — it does not detect guinea pig NaV1.7. The host determines which secondary you need; the reactivity list determines which samples you can use it on. ASC-008-GP is validated for mouse only. For human NaV1.7, use ASC-008 or ASC-029. Sequence homology is a prediction; validated reactivity is a result.

Blocking peptides: the two-control logic for antibody validation

A blocking peptide is the small piece of protein the antibody was raised against. Alomone lists 972 of them across its antibody range, ordered separately from the antibody. Here is how you use one: mix the antibody with its matched peptide before you stain. The peptide fills the antibody's binding site, so the antibody can no longer grab anything else. Run that side by side with your normal stain. Any signal that disappears was coming from the binding site; any signal still sitting there is background.

Why this matters for a channel like NaV1.7: voltage-gated sodium channels are large membrane proteins — around 230 kDa — and each one has eight close relatives sharing stretches of its sequence. Antibodies against them are raised against short peptides, often around 15 residues. That combination makes for blots that are rarely one clean band, and a matched NaV1.7 blocking peptide helps you work out which band to trust.

But it only takes you so far. It shows the signal came from the antibody's binding site. It does not show the signal is your target. If the antibody also recognizes some other protein through that same site, the peptide blocks that binding too — so the wrong band disappears as well, and looks every bit as convincing as the right one. To show the signal really is NaV1.7, you need a control that ties it to the gene rather than to the antibody: tissue or cells where SCN9A has been knocked out or knocked down. If the signal vanishes there, it was NaV1.7.

In practice, run both where you can and the peptide where you can't. For this family: NaV1.7/SCN9A Blocking Peptide (BLP-SC008, pairs with ASC-008), NaV1.7 (extracellular), Human NaV1.7 (extracellular), and a Pan NaV Blocking Peptide spanning SCN1A–SCN11A.

Arm 2 — Peptide toxins: what does the channel actually do?

Venom peptides evolved under selection pressure to discriminate between closely related channel isoforms. That is exactly the problem medicinal chemistry struggles with, and it is why spider and cone-snail peptide toxins remain the sharpest pharmacological tools for NaV subtypes.

Read that last column carefully, because it is the honest version of the story. Hd1a is the NaV1.7-directed tool. GpTx-1 prefers NaV1.7 but has real NaV1.4 and NaV1.5 activity — so a GpTx-1 effect in a mixed preparation is not automatically a NaV1.7 effect. SxIIIC is a broad-spectrum NaV blocker despite NaV1.7 appearing in its target list; it is a useful pan-NaV tool and a poor selectivity argument. Choosing between them is the experiment.

Mechanistically these are mostly gating modifiers: they bind voltage-sensor domains and shift channel activation, rather than plugging the pore the way tetrodotoxin does. The distinction shows up directly in an electrophysiology trace — a pore blocker reduces current amplitude, a gating modifier moves the voltage dependence.

Arm 3 — Small-molecule NaV1.7 blockers: why one blocker is never enough

Look again at the toxin table. Only Hd1a is listed for NaV1.7 alone; GpTx-1 also hits NaV1.4 and NaV1.5, SxIIIC hits five isoforms, and Cd1a hits CaV2.2. No single blocker in that list is a clean NaV1.7 experiment by itself. The way out isn't to hunt for a perfect blocker — it's to use two that can't be wrong in the same way.

XEN907 is a small-molecule NaV1.7 blocker on a spiro-oxindole scaffold — chemistry from the era when NaV1.7 was the most contested analgesic target in the industry (Bagal et al., Bioorg Med Chem Lett 2014). Functionally it does the same thing a toxin does: binds the channel, reduces the current. Same rig, same trace. That is not the reason to run it.

The reason is that it goes wrong in a different direction. A peptide toxin is several kilodaltons, locked in shape by disulfide bonds, and cannot cross a membrane — it only ever reaches sites on the outside of the cell, and when it misbehaves it usually misbehaves within the channel family, on another isoform with a similar voltage sensor. A small molecule is a few hundred daltons and gets in everywhere. That is its advantage — it reaches sites a toxin physically cannot, and it works in tissue and in vivo where a peptide may not — and its liability: it can reach proteins a toxin was never able to touch.

The two therefore share very little in the way of failure modes. If your effect disappears with both, the overlap between "things a spider peptide hits" and "things a spiro-oxindole hits" is narrow enough that NaV1.7 is what's left standing. If it disappears with only one, you have an off-target to track down — and the small molecule is the first place to look, because it goes more places.

The same three arms at KV1.3 and CaV2.2

NaV1.7 is not a special case. The detect / block / perturb triad is available across the Alomone catalog wherever venom happened to evolve against the target — and it is deepest at two channels that could hardly be further apart in biology.

KV1.3 antibody, toxin & blocker — the immunology target

KV1.3 (KCNA3) is a voltage-gated potassium channel that sets membrane potential in effector memory T cells. Blocking it suppresses their activation without broadly immunosuppressing the patient, which made it a target in autoimmunity (Wulff et al., J Clin Invest 2003). It is the single best-equipped target in this catalog.

• Detect — Anti-KV1.3 (KCNA3) (APC-002, intracellular) and Anti-KV1.3 (extracellular) (APC-101), the latter in FITC, PE, and Biotin conjugates for flow cytometry, plus a guinea pig host (APC-101-GP) for multiplexing alongside rabbit primaries.
• Block — roughly seventeen toxins, led by ShK from the sun anemone Stichodactyla helianthus and its engineered analog ShK-186 (dalazatide), which reached clinical evaluation (Chi et al., Toxicon 2012). Also HsTx1 and its selectivity-engineered variant HsTX1[R14A], Agitoxin-2, Margatoxin, Spinoxin, OsK-1, Hongotoxin-1, and Charybdotoxin.
• Perturb — UK-78282 hydrochloride, reported at KV1.3 and KV1.4.

A toxin that stops being a blocker. ShK is also available as ShK-ATTO Fluor-590 and ShK-Biotin, and Agitoxin-2 as Agitoxin-2-Cys-TAMRA. A labelled toxin collapses the first two arms into one reagent: it binds the functional, correctly folded, surface-exposed channel and reports its location — where an antibody binds an epitope whether or not the channel works. For surface-channel counting by flow cytometry or live imaging, that difference is worth having.

CaV2.2 antibody & ω-conotoxin — the pain target, again

CaV2.2 (CACNA1B) is the N-type calcium channel at presynaptic terminals of nociceptive neurons. Block it and neurotransmitter release from those terminals falls. It carries the strongest venom-peptide story in pharmacology.

• Detect — Anti-CACNA1B (CaV2.2) (ACC-002, human/mouse/rat, IF/IHC/IP/WB) with a matched CACNA1B/CaV2.2 Blocking Peptide.
• Block — ω-Conotoxin MVIIA from Conus magus — catalogued under its development code SNX-111 and its drug name, ziconotide. Alongside it: ω-Conotoxin GVIA, MVIIC, CVIA, CVIF, FVIA, MoVIA, Bu8, SO3, RVIA, and SVIB — eleven ω-conotoxins from ten cone-snail species, plus the spider peptide ω-Grammotoxin SIA. MVIIC is also stocked in ATTO Fluor-647N and Biotin.
• Perturb — PD 173212 and GV-58 — the latter notable for pushing the channel in the opposite direction to every blocker above.

ω-Conotoxin MVIIA is the reason the venom-peptide argument is not academic: a peptide from a marine snail became an approved intrathecal analgesic. Cd1a, listed in the NaV1.7 section, is also reported at CaV2.2 — the two targets cross-link in the catalog exactly as they do in the pain literature.

Coverage by target — at a glance

The full Alomone Labs range on BioHippo spans 3,030 products across antibodies, venom peptide toxins, and small molecules. Specifications, epitope regions, species reactivity, validated applications, and current pricing are stated on each linked product page — confirm those before purchase. This note is a selection guide, not a datasheet.

Frequently asked questions

What is NaV1.7?

NaV1.7 is a voltage-gated sodium channel encoded by SCN9A, expressed mainly in peripheral sensory and sympathetic neurons. Its slow closed-state inactivation makes it a threshold amplifier for pain signalling, which is why loss- and gain-of-function SCN9A mutations cause, respectively, congenital pain insensitivity and inherited pain disorders.

Which NaV1.7 antibody should I use — intracellular or extracellular?

Use an extracellular NaV1.7 antibody (ASC-027 for mouse, ASC-029 for human) when you need to label surface channel on live, intact cells or study trafficking. Use the intracellular ASC-008 when you are measuring total channel protein by Western blot or in permeabilized cells. A channel can be abundant in lysate yet absent from the membrane, so the epitope you choose determines which question you can answer.

Is NaV1.7 expressed in the brain?

NaV1.7 is predominantly peripheral — dorsal root and trigeminal ganglia, sympathetic neurons, and olfactory sensory neurons. It is not a major central (CNS) isoform; NaV1.1, NaV1.2, and NaV1.6 dominate there. This peripheral restriction is part of what made NaV1.7 attractive as an analgesic target.

What is a selective NaV1.7 blocker, and is there a truly selective one?

No single reagent is perfectly selective. Among peptide toxins, Hd1a is the most NaV1.7-directed, while GpTx-1 and SxIIIC also hit other NaV isoforms. The small-molecule XEN907 blocks NaV1.7 but has a different off-target profile. The reliable approach is to pair a peptide toxin with a chemically unrelated small molecule: because their failure modes barely overlap, an effect blocked by both is strong evidence for NaV1.7.

How do I validate an ion-channel antibody with a blocking peptide?

Pre-incubate the antibody with its matched blocking peptide, then stain in parallel with an unblocked control. Signal that disappears came from the antibody's binding site; residual signal is background. Because a blocking peptide cannot distinguish on-target from off-target binding through the same site, confirm identity with an SCN9A (or relevant gene) knockout/knockdown control wherever possible.

Why are venom peptide toxins better than small molecules for isoform selectivity?

Venom peptides evolved to discriminate between closely related channel isoforms, so spider and cone-snail toxins are often sharper than medicinal-chemistry compounds at telling NaV, KV, and CaV subtypes apart. Small molecules trade some of that selectivity for membrane permeability and in vivo activity, which is why the two classes are complementary rather than redundant.

All products described are supplied by Alomone Labs and are For Research Use Only — not for diagnostic or therapeutic use. References to ziconotide and dalazatide describe the pharmacological history of the parent peptides and do not indicate any clinical use of the research-grade reagents offered here. Target assignments, epitope regions, species reactivity, and validated applications are drawn from the manufacturer documentation on each linked product page; confirm current specifications before purchase.