Neuromedin U-8: gut-brain peptide fragment (NMU-8)
A short natural peptide found in the gut and brain, studied in the lab for its effects on pain and mood-related signals and its links to pancreatic cancer research.
- Class
- Endogenous neuropeptide fragment (canine-derived)
- Status
- No approved therapeutic status identified
- Best-supported effect
- Structural characterization and reported pharmacological activity in isolation study (species: dog); specific findings not individually extracted in this card
- Main caveat
- Evidence content is limited to a single vendor catalog entry and one 1991 isolation paper; no assay, animal experiment, or human data are individually extracted in this card
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Neuromedin U-8 (NMU-8) is the biologically active C-terminal fragment of neuromedin U, a neuropeptide first isolated and characterized in mammalian gut and brain tissue. Neuromedin U was named for its potent uterine-contracting activity in early pharmacological assays; the "-8" designation refers to the processed short form, whose seven-residue sequence (FLFRPRN) corresponds to the conserved C-terminal segment shared across human, rat, mouse, dog, and chicken neuromedin U isoforms (Minamino, Kangawa, Matsuo 1985, as referenced in the EMBO J structural atlas). The full-length precursor pro-NMU is cleaved by prohormone convertases at defined processing sites to yield the mature bioactive peptide; the fourth processing site generates the C-terminal amide (–NH₂) that caps the native peptide — that amide is absent from the stored seven-letter sequence FLFRPRN but is present on the biologically characterized form.
History
Neuromedin U was first described in the 1980s from porcine spinal cord, and the canine form was later isolated, structurally characterised, and its pharmacological activity assessed by O'Harte and colleagues (Peptides, 1991). The precursor processing pathway was systematically mapped by Kitabgi (Journal of Molecular Medicine, 2006), who showed that prohormone convertases differentially cleave pro-neurotensin/neuromedin N — a related pro-peptide — in tissue- and cell-line-specific patterns, illuminating how the mature short forms are generated from their precursors. The structural basis of receptor engagement in this peptide family was substantially advanced by White and colleagues (Nature, 2012), who resolved the structure of an agonist-bound neurotensin receptor, and subsequently by Deluigi and colleagues (Science Advances, 2021), whose crystal structures of NTSR1 bound to small-molecule full agonists, partial agonists, and inverse agonists revealed the structural determinants of graded receptor activation.
What it does
NMU-8 carries the conserved C-terminal sequence (Phe-Leu-Phe-Arg-Pro-Arg-Asn) that is shared across mammalian and avian neuromedin U isoforms and that is considered the pharmacophoric core responsible for biological activity. Across species, NMU sequences all terminate in this FLFRPRN motif, suggesting strong evolutionary conservation of the C-terminal region (EMBO J structural atlas, doi:10.1038/sj.emboj.7600526). The pharmacological activity of the canine neuromedin U form — encompassing the same conserved C-terminal — was characterised by O'Harte and colleagues (1991).
Evidence
- Human: No human clinical trials are reported in the dossier for the isolated NMU-8 fragment.
- Animal: Pharmacological activity of the dog neuromedin U peptide, which shares the FLFRPRN C-terminal sequence, was characterised in early work by O'Harte and colleagues (Peptides, 1991).
- In vitro: Crystal structures of the neurotensin receptor 1 (NTSR1), the card's assigned target, with agonist and non-agonist ligands were resolved by White and colleagues (Nature, 2012) and Deluigi and colleagues (Science Advances, 2021), providing structural context for ligand engagement at this receptor class.
Mechanism
NMU-8 is a seven-residue peptide (FLFRPRN) corresponding to the conserved C-terminal segment of full-length neuromedin U. The native bioactive form carries a C-terminal amide cap (–NH₂) generated when prohormone convertases cleave the precursor at the fourth processing site, with glycine serving as the amide donor; this modification is not encoded in the stored raw sequence. The FLFRPRN core is invariant across human, rat, mouse, dog, and chicken NMU sequences, consistent with it constituting the minimal receptor-engagement motif (EMBO J structural atlas). The card's assigned target is NTSR1 (neurotensin receptor type 1), a class A GPCR whose agonist-bound structure and ligand-recognition determinants have been characterised crystallographically (White et al., Nature, 2012; Deluigi et al., Science Advances, 2021).
Open questions
- The structural basis of NMU-8 binding to its receptor(s) has not been resolved at atomic resolution.
- Activity of the isolated seven-residue fragment (vs. the longer NMU forms) in human cell systems has not been reported in the available literature.
- The contribution of the C-terminal amide cap to receptor selectivity and potency of NMU-8 has not been systematically quantified in published sources available in the dossier.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Could this short fragment suppress appetite as well as the full neuromedin U hormone but with less stress and anxiety as side effects?
If true, NMU-8 or a stabilized version could become a starting point for obesity drugs that curb hunger without triggering the anxiety and stress responses that have held back full-length neuromedin U from clinical use.
Could this short gut peptide also bind the neurotensin receptor in addition to its own receptors?
If it does, NMU-8 could act through an extra pathway not yet mapped, which might help explain uneven responses to neuromedin U in animal studies and point to new drug targets. This is an untested prediction from a structure model, not a confirmed interaction.
Does this small peptide preferentially activate one of its two receptor subtypes, and does the missing chemical cap change that preference?
Knowing which subtype NMU-8 prefers could help design selective drugs that, for example, curb appetite without gut side effects. The specific binding-pocket explanation here is a proposed idea that would need experimental testing.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9191594123840332 | boltz-2 |
| ranking score | 0.7879095673561096 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 1.067 | global PDE — lower = better |
| disorder | NaN | fraction disordered |
▸3-letter notation
▸recipeboltz-2 1.0
| parameter | value |
|---|---|
| model | boltz-2 1.0 |
| weights | — |
| hardware | nvidia_nim_api |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | none |
| diffusion samples | 1 |
| runtime | — |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
▸citationbibtex
@peptide{pep10539,
sequence = {FLFRPRN},
target = {ntsr1},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}