Substance P: the body's own pain and inflammation signal
A natural signaling molecule made in the nervous and immune systems that transmits pain signals and triggers inflammation; not a drug, used as a research tool to study pain and stress.
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.
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Endogenous peptide — produced naturally and routinely synthesized for research
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Endogenous peptide — receptor binding and activity established in published literature
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What this is
Substance P is a short, 11-amino-acid peptide that the body makes and releases in the nervous system and immune system. It is one of the body's own signaling molecules for pain, inflammation, and stress responses. Substance P belongs to a family called the tachykinins — a group of structurally related neuropeptides — and is considered the founding member of that family, with Steinhoff and colleagues (Physiological Reviews, 2014) describing it as a "pioneering neuropeptide" whose study has informed our understanding of neuropeptide biology more broadly. It is encoded by the TAC1 gene and is found across a wide range of species, including mammals, birds, and fish (Steinhoff et al. 2014; WAUGH et al. 1993).
The stored sequence (RPKPQQFFGLM) represents the backbone of the peptide. The active form carries a C-terminal amide (-NH₂) that is not visible in that raw string; this modification is documented in structural studies of both mammalian and non-mammalian Substance P (WAUGH et al. 1993; Steinhoff et al. 2014).
History
Substance P was first detected as a biological activity in extracts of horse brain and intestine — an early observation that placed it simultaneously in the nervous system and the gut (Steinhoff et al. 2014). It went on to become one of the most intensively studied neuropeptide families in biomedical research. Decades of investigation into tachykinin signaling, receptor trafficking, and regulation have made Substance P a reference point for understanding how peptide neurotransmitters work. Its evolutionary conservation — with closely related sequences identified in the dogfish brain (WAUGH et al. 1993) and tree shrew nervous system (Petruzziello et al. 2012) — underscored its fundamental biological role.
What it does
Substance P acts throughout the body as a signaling molecule that communicates between the nervous and immune systems. Its best-characterized role is in transmitting pain signals: it is released from sensory nerve fibers and activates the neurokinin-1 (NK-1) receptor, which is expressed widely in the central nervous system and peripheral tissues. Beyond pain, Steinhoff and colleagues (2014) documented Substance P involvement in immune responses, gastrointestinal function, respiratory physiology, and urogenital signaling.
Substance P also plays a role at the intersection of the nervous and immune systems. Miao and colleagues (BBA General Subjects, 2020) described its involvement in neuro-immune crosstalk, including modulation of inflammation, responses in asthma, and antimicrobial host defense. The peptide's structural features — positively charged residues at the N-terminus and hydrophobic residues at the C-terminus, forming an amphipathic arrangement — are thought to contribute to these immunomodulatory properties (Miao et al. 2020).
Evidence
- Human: Substance P is an endogenous human neuropeptide; its biology has been extensively characterized in human tissue studies and through pharmacological investigation of NK-1 receptor antagonists. Clynen and colleagues (Molecular Neurobiology, 2014) identified it as a target relevant to anticonvulsant drug development.
- Animal: Steinhoff and colleagues (Physiological Reviews, 2014) reviewed a large body of animal research documenting Substance P's roles in nociception, stress, anxiety, inflammation, and gastrointestinal physiology across rodent and other animal models.
- In vitro: Steinhoff and colleagues (2014) reported Substance P stimulation of interleukin-8 expression in human colonic epithelial cells and CFTR-dependent fluid secretion in mouse tracheal submucosal gland preparations. Miao and colleagues (2020) characterized its immunomodulatory activity in cell-based assays.
Known effects
- Pain signaling — Endogenous neurotransmitter at NK-1 receptors; nociceptive role well-established in animal and human tissue studies (Steinhoff et al. 2014)
- Neurogenic inflammation — Released from sensory afferents; activates mast cells and drives local inflammatory responses (Steinhoff et al. 2014)
- Immune modulation — Neuro-immune crosstalk; involved in inflammatory signaling and antimicrobial responses (Miao et al. 2020)
- Gastrointestinal function — Stimulates fluid secretion and epithelial cytokine release in gut preparations (Steinhoff et al. 2014)
- Anxiety and stress — Stress-sensitive release in the amygdala; modulation of anxiety-related behavior in rodent models (Steinhoff et al. 2014)
- Anticonvulsant research target — Identified among neuropeptide targets for antiepileptic drug development (Clynen et al. 2014)
Mechanism
Substance P is encoded by the TAC1 gene and derives from alternate processing of the pre-protachykinin-A transcript, one of three Tac genes; the tachykinin family as a whole signals through three neurokinin G protein-coupled receptors (Steinhoff et al. 2014). Substance P shows highest affinity for the neurokinin-1 receptor (NK-1, also designated TACR1), which is expressed in discrete neuronal populations throughout the central nervous system and in peripheral tissues including the gut, airways, and immune cells (Steinhoff et al. 2014).
The peptide's amphipathic structure — an N-terminal region bearing positively charged residues (Arg, Lys) and a C-terminal region dominated by hydrophobic residues (Phe, Phe, Gly, Leu, Met) — is relevant both to receptor engagement and to the antimicrobial and membrane-active properties noted by Miao and colleagues (2020). The C-terminal amide, absent from the raw stored sequence, is characteristic of the active form and shared with other tachykinins (WAUGH et al. 1993; Steinhoff et al. 2014).
Related peptides
Substance P is the prototypical member of the mammalian tachykinin family. Related tachykinins that signal through the neurokinin receptor family include neurokinin A and neurokinin B, which also derive from TAC gene processing and share the C-terminal -FFGLM-NH₂ motif (Steinhoff et al. 2014). Structurally distinct tachykinin variants have been characterized from non-mammalian species, including dogfish Substance P (WAUGH et al. 1993).
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.961114227771759 | boltz-2 |
| ranking score | 0.7589403986930847 | boltz-2 |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep04471,
sequence = {RPKPQQFFGLM},
target = {tacr1},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}