Neurotensin fragment: brain signaling & pain research tool (Neurotensin [3-13])
A shortened piece of the natural brain peptide neurotensin that binds its receptor just as well as the full version; used in labs to study dopamine signaling, pain pathways, and certain pancreatic cancers. Used only as a lab research tool.
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
Neurotensin [3-13] (NT[3-13]) is an 11-residue fragment of neurotensin, a 13-amino-acid neuropeptide first isolated in 1973 from bovine hypothalamus. The full parent peptide was named for where it was found (neuronal tissue) and one of its most striking effects (vasodilation causing a drop in blood pressure). NT[3-13] retains the entire C-terminal region of neurotensin that is responsible for binding and activating the neurotensin receptor type 1 (NTSR1). It is used primarily as a pharmacological research tool to probe NTSR1 function in the brain, particularly in circuits governing dopamine signaling and pain, and to study the receptor's role in certain cancers where NTSR1 is abnormally overexpressed.
History
Neurotensin itself was purified and sequenced by Carraway and Leeman in the early 1970s, establishing that the gut–brain peptide is distributed across both the central nervous system and the gastrointestinal tract. The shorter fragments — including NT[3-13] and NT[4-13] — were identified later through studies of how neurotensin is naturally processed from its precursor proteins. Carraway and colleagues (Regulatory Peptides, 1987) showed that pepsin treatment of feline CNS and intestinal substrates generates NT-(3–13) as the predominant immunoreactive product, accounting for roughly 40% of total cleavage products, alongside smaller amounts of NT-(4–13). This established that NT[3-13] is not merely a synthetic convenience — it is a naturally occurring processing product of the neurotensin precursor in tissues where the parent peptide is made.
The broader significance of the fragment became clearer as structure–activity studies demonstrated that the minimal sequence required for NTSR1 binding and activation resides in the C-terminal portion of neurotensin. White and colleagues (Nature, 2012) solved the first crystal structure of an agonist-bound NTSR1 using the hexapeptide NT[8-13], confirming that the C-terminus drives receptor engagement. NT[3-13], which encompasses and extends that core, has been used throughout this body of work as one of the reference ligands to define NTSR1 pharmacology.
What it does
NT[3-13] binds and activates NTSR1, a class A G protein-coupled receptor (GPCR) that serves as the primary high-affinity receptor for neurotensin in the brain and peripheral tissues. Through NTSR1, neurotensin and its fragments modulate dopamine neuron activity — particularly in the ventral tegmental area (VTA) and substantia nigra, the brain regions whose dopamine circuits underlie movement, motivation, and reward. Pharmacological activation of NTSR1 also produces analgesia (pain suppression), hypothermia, and effects that resemble some actions of antipsychotic drugs, all independent of the opioid system.
In cancer biology, NT[3-13] serves as a probe for NTSR1-expressing tumor cells. NTSR1 is overexpressed in a range of malignancies, and agonist stimulation through this receptor drives proliferative and survival signaling cascades in those cells.
Evidence
- Human: No clinical trials of NT[3-13] in humans have been conducted or registered; the fragment is a laboratory research tool, not a clinical drug candidate. NTSR1 overexpression in human cancers (including colon and pancreatic tumors) has been documented in tissue studies (Bugni et al., International Journal of Cancer, 2012).
- Animal: NT[3-13] and related C-terminal fragments have been used to interrogate NTSR1 pharmacology in rodent systems. Besserer-Offroy and colleagues (European Journal of Pharmacology, 2017) characterized the signaling signature of NTSR1 activated by endogenous neurotensin ligands, including fragment-length variants, across Gαq, Gαi, GαoA, and Gα13 pathways and β-arrestin 1/2 recruitment.
- In vitro: Crystal structures of NTSR1 bound to agonists — using NT[8-13] as the canonical peptide agonist — have been obtained at 2.8 Å resolution (White et al., Nature, 2012) and subsequently elaborated with small-molecule comparator ligands (Deluigi et al., Science Advances, 2021). These structures define the binding pocket architecture and explain why C-terminal neurotensin fragments are the functional pharmacophore at NTSR1. NT[3-13] retains this pharmacophore region in full.
Known effects
- NTSR1 agonism — Pharmacological, in vitro and in vivo rodent studies
- Dopamine circuit modulation — Preclinical; NTSR1 expressed on VTA and substantia nigra dopamine neurons
- Analgesia (opioid-independent) — Preclinical; receptor-mediated via NTSR1
- Hypothermia — Preclinical; NTSR1-dependent effect
- Tumor NTSR1 probe — In vitro and mouse xenograft models; NTSR1 overexpressed in sporadic colon and pancreatic cancer
Mechanism
NT[3-13] engages NTSR1 by occupying the orthosteric (primary) binding pocket at the extracellular face of the receptor. Structural work by White and colleagues (Nature, 2012) using the C-terminal hexapeptide NT[8-13] — the minimal active core that NT[3-13] contains in full — showed the peptide agonist adopts an extended conformation nearly perpendicular to the membrane plane, with its C-terminus oriented toward the receptor core. Leucine at position 13 anchors to key residues deep in the pocket via salt bridge and van der Waals contacts; the two arginine residues at positions 8 and 9 contribute charge complementarity at the extracellular rim.
Agonist binding triggers a contraction of the binding pocket at the extracellular side and a cascade of conformational rearrangements through transmembrane helices 6 and 7, ultimately enabling coupling to intracellular G proteins. Besserer-Offroy and colleagues (European Journal of Pharmacology, 2017) showed that endogenous NTSR1 ligands — including neurotensin fragments — activate the Gαq, Gαi1, GαoA, and Gα13 signaling arms as well as β-arrestin 1 and 2 recruitment, producing functionally distinct downstream outcomes. Huang and colleagues (Nature, 2020) provided the cryo-EM structure of full-length human NTSR1 in complex with β-arrestin 1, revealing how phosphorylation of NTSR1's intracellular loop and C-terminus drives arrestin engagement — a conformation relevant for receptor internalization and biased signaling.
In cancer, NTSR1 agonism by neurotensin drives proliferative signaling through MAPK/ERK and NF-κB pathways; Bugni and colleagues (International Journal of Cancer, 2012) demonstrated in a mouse model that NTSR1 promotes tumor development in sporadic colon cancer, with Ntsr1-deficient mice developing significantly fewer tumors than wild-type animals under the same carcinogen exposure.
Safety signals
NT[3-13] is a research peptide with no clinical use and no formal safety database. Pharmacological studies of NTSR1 agonism in animals consistently note hypothermia and hypotension as on-target effects that complicate therapeutic translation of full NTSR1 agonists. These are receptor-mediated consequences, not toxicities unique to NT[3-13].
Regulatory status
- US: Not approved. No IND or clinical trial application. Research-only compound.
- EU: Not approved. Research-only.
- WADA: Not listed on the current prohibited list. No sport-performance relevance has been documented.
Related peptides
- Neurotensin (full-length) — the parent 13-residue tridecapeptide from which NT[3-13] is derived by natural processing and synthetic truncation; the canonical endogenous NTSR1 agonist
- Neuromedin N — a hexapeptide co-encoded on the same precursor gene as neurotensin; also a high-affinity NTSR1 ligand characterized alongside neurotensin fragments (Besserer-Offroy et al., 2017)
- See also the small-molecule NTSR1 agonist discovery work adjacent to this fragment pharmacology (Di Fruscia et al., Bioorganic & Medicinal Chemistry Letters, 2014)
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 cutting off the first two amino acids change the type of signal the receptor sends into the cell?
If true, doctors might one day have a more precise lever for pain or dopamine disorders, with fewer side effects like blood pressure drops.
Do the two prolines act like a hinge that holds the peptide in its active shape?
If true, drug designers could build rigid mimics around that hinge, potentially creating pill-like molecules that copy the peptide's effect.
Could a small fragment of a brain peptide be developed to interfere with a receptor that fuels pancreatic cancer?
If true, it could point toward a new way to study or target pancreatic cancer, a disease with very few treatment options, and might also help label tumors for imaging.
Could chopping off the first two amino acids make this peptide more selective for one receptor type?
If true, researchers and doctors could turn up or down specific biological dials more precisely, reducing unwanted effects from hitting the wrong receptor.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9154046773910522 | boltz-2 |
| ranking score | 0.7797489166259766 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.895 | 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{pep10696,
sequence = {YENKPRRPYIL},
target = {ntsr1},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}