PE22-28, also known in the published literature as mini-spadin, is a synthetic heptapeptide that selectively inhibits the TREK-1 two-pore-domain potassium channel. It is a shortened, optimised analogue of spadin, itself a naturally occurring fragment of the sortilin propeptide, and it is studied mainly in rodent models of mood-related behaviour, hippocampal neurogenesis and, more recently, stroke recovery. Compared with many peptides covered in the research-chemical literature, PE22-28 has a notably small and concentrated body of published work, almost entirely from a single research group, which this article sets out plainly alongside the structural and mechanistic detail. This article reviews PE22-28’s structure, mechanism, the published studies behind it, research applications and the handling requirements relevant to a laboratory setting.
What is PE22-28?
PE22-28 is a seven-amino-acid peptide with the sequence Gly-Val-Ser-Trp-Gly-Leu-Arg, corresponding to residues 22 to 28 of the 44-amino-acid propeptide (PE) released from sortilin, also known as neurotensin receptor 3, during its intracellular processing. Its molecular weight is approximately 774 g/mol, and it carries the CAS registry number 1801959-12-5.
PE22-28 is a deliberately shortened derivative of spadin, a 17-residue peptide (corresponding to residues 12 to 28 of the same propeptide) that had earlier been identified as a naturally occurring TREK-1 channel blocker with antidepressant-like activity in mice. PE22-28 was designed and characterised by Djillani and colleagues at the Institute of Molecular and Cellular Pharmacology (CNRS), Université Côte d’Azur, who investigated how spadin is degraded once in the bloodstream and, from that degradation profile, identified a shortened seven-residue fragment with improved receptor affinity and metabolic stability relative to the parent peptide (Djillani et al., 2017, PMC). The peptide is referred to as “mini-spadin” in the subsequent literature from the same group, and both names refer to the identical sequence.
Mechanism of action
PE22-28 acts as a selective inhibitor of TREK-1 (KCNK2), a member of the two-pore-domain potassium (K2P) channel family. TREK-1 channels contribute to the resting membrane potential and excitability of neurons, and in the original characterisation study, PE22-28 inhibited TREK-1 current in human TREK-1-expressing HEK293 cells with a half-maximal inhibitory concentration (IC50) of approximately 0.12 nanomolar, reported as several hundred-fold more potent than spadin itself, which showed an IC50 in the 40 to 60 nanomolar range in the same assay system.
TREK-1 is physically associated with sortilin at the cell membrane, and sortilin has been reported to be necessary for correct trafficking of TREK-1 to the cell surface; spadin and its shortened analogues, including PE22-28, are understood to interfere with this sortilin-TREK-1 relationship rather than acting as classical pore blockers at the channel’s conduction pathway itself, though the precise molecular point of interaction has not been as thoroughly characterised as it has for better-studied ion channel ligands. Inhibition of TREK-1 by PE22-28 has been linked, in the published behavioural work described below, to increased hippocampal neurogenesis and altered synaptic protein expression, effects consistent with TREK-1’s previously established role in neuronal excitability and mood-related behaviour in rodent models, though the downstream signalling steps connecting channel inhibition to these cellular outcomes remain an active area of investigation rather than a fully settled mechanism.
A later study examining PE22-28 in a stroke model reported what the authors described as a biphasic, dose-dependent action on TREK-1: at a very low dose, the peptide was reported to activate rather than inhibit the channel, with neuroprotective effects attributed to that activation, whereas the higher-affinity inhibitory action established in the original cell-based characterisation was observed at higher concentrations. Researchers planning experiments with this peptide should treat its concentration-dependent direction of effect as an important variable rather than assume a single, fixed pharmacological action across all conditions.
What the research shows
The founding and most detailed characterisation of PE22-28 was reported by Djillani and colleagues in Frontiers in Pharmacology in 2017. Having identified PE22-28 from the pattern of spadin degradation products in blood, the authors confirmed its TREK-1 inhibitory potency in HEK cells expressing the human channel, and went on to test it in mice using the forced swimming test and the novelty-suppressed feeding test, two standard assays of antidepressant-like behaviour. The study reported that PE22-28 retained antidepressant-like activity in both acute and sub-chronic dosing regimens, with an extended duration of action, reported at up to 23 hours compared with around 7 hours for spadin, and also reported increased markers of hippocampal neurogenesis following treatment (Djillani et al., 2017, PMC).
The only other in vivo study reporting original PE22-28 data is a 2019 paper by Pietri and colleagues in Neuropharmacology, from the same research group. Using a mouse model of focal cerebral ischaemia, the authors reported that a single low dose of PE22-28, administered by intraperitoneal injection daily for seven days beginning thirty minutes after ischaemia onset, reduced stroke-induced motor and cognitive deficits and reduced markers of post-stroke depression-like behaviour in the treated animals. The paper is notable for describing the dose-dependent, biphasic action on TREK-1 referred to above, distinguishing the low, channel-activating neuroprotective dose used in this study from the higher, channel-inhibiting doses used in the original 2017 behavioural work.
Beyond these two papers, independently replicated or third-party data on PE22-28 specifically are not available in the published literature to date; a separate 2021 study from a related research group examined sortilin-derived peptides in the context of pancreatic beta-cell survival, but readers should treat that work as part of the broader sortilin-peptide research area rather than as confirmed, independently replicated PE22-28 data, since it is not certain from available sources that PE22-28 itself, rather than a related sortilin-derived peptide, was the specific compound used. Given this, researchers should note that the pharmacological profile of PE22-28 rests on a small number of publications from a single laboratory, and should design confirmatory experiments accordingly rather than treating published findings as independently established.
Research applications
In the laboratory, PE22-28 is used mainly as a pharmacological tool for probing TREK-1 channel function, drawing directly on the electrophysiological characterisation established in the founding 2017 study. Cell-based work, typically using TREK-1-expressing HEK293 cell lines and patch-clamp electrophysiology, is used to confirm channel inhibition or, at low concentrations, the channel-activating effect reported in the later stroke study, and to compare PE22-28’s potency and selectivity against spadin and other TREK-1-modulating compounds.
Rodent behavioural models, including the forced swimming test and novelty-suppressed feeding test used in the original characterisation, are used to study mood-related and antidepressant-like behavioural responses to TREK-1 inhibition, often alongside histological assessment of hippocampal neurogenesis and synaptic marker expression. Rodent models of focal cerebral ischaemia are a second application, following directly from the 2019 stroke study, examining motor, cognitive and depression-like outcome measures after induced ischaemia with low-dose PE22-28 treatment.
Because PE22-28 and its sortilin-TREK-1 relationship sit at the intersection of ion channel pharmacology and neurotrophic signalling, it is also used, albeit on a limited published basis to date, in exploratory work on sortilin biology and its role in protein trafficking at the neuronal membrane.
Purity, storage and handling
Because degradation accelerates once reconstituted, batch-level HPLC verification matters more here than with more stable peptides. UK laboratories sourcing PE22-28 should expect a batch-specific certificate of analysis and lyophilised storage at -20°C, and those comparing suppliers should look for the same documentation from any best peptides supplier UK they consider.
Reversed-phase HPLC separates the intact heptapeptide from truncated or deletion sequences and residual synthesis by-products, and research-grade material is commonly specified at 95 to 98% purity or above. Mass spectrometry alongside HPLC confirms identity against the expected mass of approximately 774 daltons for the free peptide. A batch-specific certificate of analysis, rather than a generic product datasheet, is what links a physical vial to those results and allows unexpected experimental data to be traced back to a defined lot, which matters in particular given the dose-dependent, biphasic pharmacology described above, where small differences in effective peptide concentration could plausibly shift which direction of channel effect is observed.
Lyophilised PE22-28 should be kept sealed at -20°C for long-term storage, protected from moisture and light, and brought to room temperature before opening so that condensation does not enter the vial. Once reconstituted in sterile water or an appropriate buffer, the peptide should be divided into single-use aliquots, held at 2–8°C only for short working periods, and otherwise kept frozen, since repeated freeze–thaw cycles risk degrading the peptide. The tryptophan residue within the sequence is particularly susceptible to photo-oxidation, so amber vials or foil-wrapped storage are sensible precautions during handling. Published reconstituted-stability data specific to PE22-28 are not available in the current literature, so laboratories should validate their own working window empirically, for example by re-running HPLC on aliquots at defined time points and confirming activity in a TREK-1 electrophysiology assay.
Frequently asked questions
What is PE22-28 used for in research?
It is used mainly as a tool compound for studying TREK-1 potassium channel function, in cell-based electrophysiology and in rodent behavioural and stroke-recovery models, drawing on its origin as a shortened, higher-affinity analogue of the natural peptide spadin. It is not evaluated here as a treatment, and this article makes no claims about use in humans.
How much published research exists on PE22-28?
Published research specifically on PE22-28 is limited to two primary in vivo studies, both from the same research group at Université Côte d’Azur, covering antidepressant-like behaviour and hippocampal neurogenesis (2017) and stroke recovery (2019). There is currently no independently replicated data, and no published human studies of PE22-28 exist.
What is the difference between PE22-28 and spadin?
Spadin is the 17-residue natural peptide fragment from which PE22-28 was derived; PE22-28 is a shortened, seven-residue sequence identified from spadin’s blood degradation products. Published characterisation reported PE22-28 to be several hundred-fold more potent at inhibiting TREK-1 than spadin, with a longer reported duration of action in mice.
How should PE22-28 be stored once reconstituted?
Reconstituted PE22-28 should be divided into single-use aliquots, kept refrigerated only briefly and otherwise frozen, protected from light, and not subjected to repeated freeze–thaw cycles. Because published stability data specific to this peptide are not available, laboratories should confirm their own storage window empirically, for example by comparing HPLC profiles and TREK-1 assay activity of fresh and aged aliquots.
The PE22-28 discussed in this article is supplied for in-vitro and in-vivo laboratory research only. It is not intended for human or veterinary use, and nothing in this article should be read as guidance on administration to people or animals.
