Does tuftsin have a known receptor?

Yes — Nissen 2013 reported it signals through neuropilin-1 via the transforming growth factor beta pathway.

Does Selank have one?

No identified receptor. That is the notable asymmetry: the parent has one, the analogue built from it does not.

What is neuropilin-1?

A transmembrane co-receptor that binds several structurally unrelated ligands, involved in axon guidance, vascular biology and immune regulation.

Selank (Tuftsin Analogue)

The Parent Has a Receptor the Analogue Lacks

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-233 cited sources

Nissen and colleagues reported in the Journal of Neurochemistry in 2013 that tuftsin signals through its receptor neuropilin-1 via the transforming growth factor beta pathway — giving the parent tetrapeptide both an identified receptor and an identified downstream pathway.

Key facts

Receptor: Neuropilin-1 (NRP1)
Downstream pathway: Transforming growth factor beta
Ligand: Tuftsin, Thr-Lys-Pro-Arg
Paper: Nissen 2013 (PMID 24033337)
Journal: J Neurochem, November 2013
Selank's own receptor: Not identified

Why an identified receptor changes what can be studied

A named receptor supplies a field with its instruments. Binding can be measured, dose-response constructed, and selective blockade used to test whether an observed effect actually runs through the proposed pathway. Without one, effects can be described but not attributed — which is the position Selank, Semax, MOTS-c and DSIP all occupy on this site.

What neuropilin-1 is

A single-pass transmembrane protein that functions largely as a co-receptor rather than a conventional signalling receptor in its own right. It participates in axon guidance through semaphorin signalling, in vascular biology through VEGF signalling, and in immune regulation. It binds several structurally unrelated ligands, which is unusual and central to how it works.

Research material referenced

Selank 10mg — third-party HPLC tested

View — £24.99

Why the TGF-beta pathway is a notable destination

Transforming growth factor beta signalling governs immune regulation, tissue remodelling and, in the central nervous system, microglial state. A peptide originating in an antibody, acting through a co-receptor, onto a pathway that regulates immune tone is a coherent story rather than a collection of unrelated observations.

How this connects to tuftsin's classical activity

Tuftsin was characterised decades earlier as a stimulator of phagocytosis in macrophages and neutrophils. Identifying neuropilin-1 and TGF-beta as the route gives that long-known functional observation a molecular explanation, which is the ordinary progression of a pharmacology — activity first, mechanism later, sometimes by decades.

Why the site did not previously carry this

Because the Selank literature and the tuftsin literature are largely separate, and the analogue's articles reasonably concentrate on the analogue. Tuftsin has roughly 690 indexed records against Selank's much smaller total — around five times as many — so a good deal of relevant mechanism sits in the parent's literature rather than the compound's.

Regulatory position

Neither tuftsin nor Selank holds a marketing authorisation from the MHRA, EMA or FDA. Material supplied here is for laboratory research only, and no claim is made about immune function or any condition in any person.

Extended research context

The Selank (Tuftsin Analogue) deep dive

Deep dive: preserving a signal rather than supplying one

Selank's most specifically characterised activity is not receptor binding. Work published in the Bulletin of Experimental Biology and Medicine in 2001 and 2002 reported that it inhibits enkephalin-degrading enzymes, measured directly on plasma enkephalinase activity, thereby extending the half-life of endogenous enkephalins rather than acting at opioid receptors itself. That distinction is routinely muddled and it matters: an agonist activates the receptor wherever the drug reaches, at whatever concentration is given, while a degradation inhibitor only lets the ligand the body is already releasing persist longer. The effect is bounded by endogenous release and occurs only where that release happens. The same logic underlies DPP-4 inhibitors in the incretin field, which prolong native GLP-1 rather than supplying an analogue - and instructively, that class produces much smaller effects than the receptor agonists do.

Deep dive: what the sequence does and does not contain

TKPRPGP is unusual among research peptides for what is absent from it. There is no cysteine, so no disulfide bonds form or scramble and no reducing agent is needed. There is no methionine, so the thioether oxidation that adds 16 Da and dominates handling guidance for MOTS-c and Semax does not apply. There is no asparagine or glutamine either, ruling out deamidation. What remains is straightforward hydrolysis, and three prolines in seven residues resist even enzymatic cleavage well, because proline locks the backbone rotation peptidases require. One practical cost of that composition: no aromatic residues means almost no absorbance at 280 nm, so the standard spectrophotometric quantification method does not work on it.

Deep dive: reading a two-literature evidence base

PubMed indexes roughly 135 Selank records against about 690 for its parent peptide tuftsin - an inversion worth noticing, since most designed analogues eventually outgrow the parent they replaced. Most of the tuftsin literature is immunological and predates Selank entirely, so it is not evidence about Selank. Within Selank's own record the split is the same one Semax shows: mechanistic work in internationally indexed journals, assessable directly; clinical work concentrated in Russian-language publications, indexed by translated title and often without accessible English full text. That is evidence which is hard to verify independently, which is not the same as evidence that is absent, and not the same as evidence that is established.

Research applications

▸Enkephalin and enkephalinase pathway research
▸GABAergic receptor expression studies in rodent models
▸BDNF expression research, including intranasal administration routes
▸Comparative work on proline-stabilised peptide design
▸Tuftsin and immunopeptide structure-activity research

Handling checklist

✓Store lyophilised material cold, dry and protected from light
✓No reducing agent needed — the sequence contains no cysteine
✓No methionine oxidation to expect; a +16 Da satellite warrants explanation
✓Do not rely on 280 nm absorbance — there are no aromatic residues
✓Introduce diluent gently against the vial wall; swirl rather than shake
✓Aliquot to avoid repeated freeze-thaw cycles

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Describing Selank as an opioid or opioid agonist

Fix: Reported work describes inhibition of enkephalin-degrading enzymes, not receptor binding. It preserves endogenous enkephalins rather than supplying an agonist.

✗ Treating the benzodiazepine contrast as a safety claim

Fix: The mechanistic difference is real — expression-level rather than direct allosteric modulation — but it supports no comparative claim about safety or dependence.

✗ Citing tuftsin literature as evidence about Selank

Fix: Tuftsin has roughly five times more papers, most of them immunological and predating Selank. They are different compounds.

✗ Reading a BDNF expression change as a demonstrated outcome

Fix: The work measured expression in rat hippocampus. Expression is upstream of function and upstream again of any clinical claim.

✗ Treating Russian registration as equivalent to MHRA approval

Fix: Authorisations are jurisdictional and do not transfer. Selank has never been assessed by the MHRA, EMA or FDA.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Does tuftsin have a known receptor?: Yes — Nissen 2013 reported it signals through neuropilin-1 via the transforming growth factor beta pathway.
Does Selank have one?: No identified receptor. That is the notable asymmetry: the parent has one, the analogue built from it does not.
What is neuropilin-1?: A transmembrane co-receptor that binds several structurally unrelated ligands, involved in axon guidance, vascular biology and immune regulation.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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