Peptide-based immunotherapy is a promising cancer treatment due to its scalability and patient-centered approach; therefore, there is an increasing focus on discovering neoantigens or modified peptides which could elicit a better immune response. We recently found that the methionine sulfoxide variant of YMDGTMSQV, an immunogenic tyrosinase derived epitope, elicits a stronger immune response compared to the native one. Here, we address the separation of six MHC I-restricted tyrosinase-derived peptides methionine sulfoxide stereoisomers (YMNGTMSQV, YMDGTMSQV, YMQGTMSQV, YMDGVMSQV, FMNGTMSQV, FMDGTMSQV) using offline two-dimensional high-performance liquid chromatography coupled with UV/Vis-Circular Dichroism detection. For all analyzed peptides, using our methodology, we observed that placing the sulfoxide on the methionine in sixth position results in no enantiodiscrimination, suggesting the net contribution of the N-terminus tyrosine or phenylalanine π electrons in separation. We show how modifying the amino acids in the vicinities of the methionine-sulfoxide residues results in the ablation of the chiral discrimination. We also render our methodology analytical to semi-preparative level. We describe the stereoisomers stability and capture differences regarding their propensity towards oxidation, our results suggesting that the substitution of the N-terminus tyrosine to phenylalanine could be involved in this process. We analyzed the tandem mass spectrometry fragmentation patterns of the separated optic isomers and search for clues about their discrimination. Moreover, we found that the stereoisomers are similar recognized by specific HLA compared with the racemic variant. Our methodology could be valuable for potential applications in an enantiomer-specific peptide-based immunotherapy selection.

Background and Objectives: Toll-like receptors (TLRs) are pattern recognition receptors with an essential role in regulating both the innate and adaptive immune response. Given their pleiotropic effects in mounting an immune response, previous studies have proposed targeting these TLRs might render alternative strategies for cancer therapy. Synthetic immune response modifiers, such as imidazoquinolines, stimulate the immune cells by activating Toll-like receptors, particularly TLR7/8 receptors, consequently mounting an immune response. Agonists of this class activate, via TLR-mediated signaling, dendritic and B cells, as well as myeloid cells and T cells, thus exhibiting good prospects for cancer immunotherapy. In the present study, we sought to evaluate the effect of imiquimod and gardiquimod, two TLR 7 and 7/8 agonists, respectively, on tumor growth and phenotype of NK cells associated with melanoma. Materials and Methods: We generated a syngeneic model of melanoma in C57BL/6J mice by subcutaneously injecting murine melanoma cells and monitoring tumor growth. Starting on day 8 or 14, we applied TLR agonists either intratumorally or topically and followed the tumor dynamics and NK cell-associated pattern. Results: Our results suggest that both TLR agonists displayed an antitumor effect along with a phenotypically activated profile of NK cells. Both imiquimod and gardiquimod treatment inhibited tumor growth, with gardiquimod showing an increased potency compared to imiquimod. Conclusions: This implies that TLR agonists like imiquimod and gardiquimod could serve as neoadjuvant, adjuvant, or complementary immunotherapeutic agents in melanoma therapy.

Ovarian cancer (OC) is the 8th most common cancer in women. Most patients with high-grade serous OC present with intraperitoneal disseminated disease when diagnosed, due to mild symptoms in earlier disease stages. They respond efficiently to cisplatin or taxol-based compounds in the front-line treatment; however, resistance emerges in the majority of cases, which allows tumors to progress. There is an urgent need for improved treatment to increase patients’ survival. Tissue transglutaminase (TG2) is a protein overexpressed in many solid tumors, including ovarian; it interacts with fibronectin (FN) in the extracellular matrix and promotes OC intraperitoneal dissemination. This makes TG2 a promising target for treatment. We previously identified MT4 as a promising small molecule inhibitor (SMI) able to disrupt TG2-FN protein-protein interaction, prevent cancer cell adhesion and spheroid formation, and sensitize OC cells to chemotherapeutic drugs, such as paclitaxel (Sima LE et al., Mol Cancer Ther., 2019). We recently investigated the effect of 5 new MT4 analogues on OC cells behavior. We found that compound #3011 completely prevented spheroids formation, similar to Tgm2 gene excision, while #3002 decreased cell adhesion onto FN. We used phosphoproteomics to analyze the adaptive signaling of OC cells treated with MT4 that escape treatment. New promising molecular TG2 co-targets for OC treatment have been identified as effectors of MT4 escape pathways: sirtuins and p21-activated kinases (PAKs). Combination of signaling inhibitors and TG2-directed SMIs induce OC cell death in both 2D and 3D conditions, with potential for future therapeutic use. Our multiplex IHC data shows that in OC tumors TG2 is expressed by cancer cells, as well as by α-SMA+ CAF subset. Therefore, we next sought to test the effect of TG2 drug targeting on OC cells-fibroblasts 3D co-cultures. Our results showed that MT4 prevents heterospheroid self-assembly in vitro, which indicates potential disruption in tumor-stroma communication using TG2-directed therapies. In parallel, we developed new tools to test drug combinations, as well as radiation therapy regimens for their potential to inhibit cancer spreading. We produced a new glass microfluidic chip and adapted a miniaturized mesothelial clearance assay for live cell imaging. We obtained new SKOV3 and SKOV3-TG2KO LifeAct+ stable cell lines to allow real time imaging measurements of OC cell behavior. Subpopulations were sorted based on actin-GFP expression level and characterized by cell motility quantification. Cell lines with behavior similar with parental cells were selected for further use. We currently use these tools to investigate the potential of TG2 targeting to enhance response of cancer cells to new FLASH radiation sources (Orobeti S et al, Sci. Rep., 2024), such as very high energy electrons generated with a high-intensity laser plasma accelerator system. Monica Tudor, Cristian Munteanu, Gabriela Chiritoiu, Stefana Orobeti, Alexandra Bran, Florin Jipa, Felix Sima, Gary E. Schiltz, Daniela Matei, Livia Elena Sima. Small molecule inhibitors targeting TG2 in ovarian cancer and identification of drug escape pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3867.

Introduction:Acute Myeloid Leukemia (AML) is a group of very aggressive hematological malignancies, with dismal long-term survival rates and little therapeutic recourse presently. The transmembrane ligand B7-H3 is a known therapeutic target, biomarker of response and correlated with an unfavorable prognosis in several malignancies, including AML, due to acquired resistance to immune checkpoint-targeting therapies. Therefore, developing therapeutic strategies with improved efficacy to overcome this obstacle constitutes an unmet need. Our study entails the design, production and in vitro testing of a novel recombinant Affibody with high affinity for B7-H3 coupled with the cytotoxic peptide Magainin-2, known for its membranolytic properties and potent antimicrobial and antitumor activity. Methods:We expressed the conjugate in Escherichia coli, affinity purified it and confirmed its sequence by nanoLC-MS/MS. B7-H3-positive AML representative THP-1 cells and B7-H3-negative B-lymphoblastic RAJI cells were used for the experiments. The IC50 of the cytotoxic conjugate was determined through MTS assay and its necrotic, apoptotic and antiproliferative activities were evaluated by flow cytometry and Western blot. Results:Overall, the results show that our cytotoxic anti-B7-H3 affibody possesses strong antiproliferative and cell death-inducing activity that is highly specific to B7-H3-expressing AML cells (IC50 against THP-1 cells was 26.35 µM). Moreover, this observed activity of our conjugate is significantly more potent than the previously described activity of Magainin-2 alone. Conclusion:In conclusion, we designed, produced and evaluated a novel anti-B7-H3 cytotoxic affibody-drug conjugate (AfDC) that, from these preliminary in vitro data, shows high potential for translation to the therapy of AML, warranting further preclinical and translational exploration, including pharmacokinetic and in vivo efficacy studies.

The selective detection of dithiocarbamate fungicides in food and agricultural products presents significant analytical challenges. While Surface-enhanced Raman spectroscopy (SERS) has been extensively investigated to address this, detection systems based on enzymatic inhibition remain underexplored. Using thiram as a model dithiocarbamate, the present work explores the potential application of a cold-active aldehyde dehydrogenase from Flavobacterium PL002 for the development of specific, inhibition-based analytical methods. A molecular modelling and docking study confirmed that thiram fits into the binding pocket of the enzyme. An irreversible inhibition mechanism was inferred for thiram based on enzymatic kinetics studies. The mechanism was supported by SERS, mass spectrometry measurements and tests with reducing agents. A simple assay for the detection of the fungicide was developed and compared to a SERS-based procedure. The advantages and the practical limitations of the two methods were revealed by studying the detection of thiram from the surface of fungicide-spiked tomatoes. By coupling enzymatic inhibition with SERS, the selectivity for the detection of individual fungicides can be increased, as illustrated by comparing thiram with ziram, a structurally related compound. The study serves as basis for the development of analytical methods for the selective detection of thiram.

The ERAD glycoprotein misfolding checkpoint complex de-mannosylates misfolded glycoproteins, targeting them for retrotranslocation, ubiquitination, and proteasomal degradation. The checkpoint complex is a heterodimer comprising an Endoplasmic Reticulum Degradation Enhancing Mannosidase (EDEM) and a Protein Disulfide Isomerase (PDI). We determined Cryo-EM structures of the Chaetomium thermophilum, (Ct) CtEDEM:CtPDI heterodimer and its complex with a classic ERAD substrate, the NullHongKong variant of α1-antitrypsin (A1AT-NHK). The CtEDEM:CtPDI structure shows the EDEM catalytic domain nested within the PDI arc-shaped thioredoxin domains. In the complex with the client, A1AT-NHK contacts a hydrophobic surface in the EDEM C-terminal flexible domains. Redox chemistry between EDEM and PDI disulfide bonds yields an oxidized, demannosylation-competent EDEM and a reduced PDI, enabling the latter to act as the ERAD reductase in facilitating client retrotranslocation. ### Competing Interest Statement The authors have declared no competing interest.

In this study, hybrid bio-nanoporous peptides loaded onto poly(N-isopropylacrylamide-co-butylacrylate) (pNIPAM-co-BA) coatings were designed and obtained via matrix-assisted pulsed laser evaporation (MAPLE) technique. The incorporation of cationic peptides magainin (MG) and melittin (Mel) and their combination was tailored to target synergistic anticancer and antibacterial activities with low toxicity on normal mammalian cells. Atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy as well as contact angle and surface energy measurements revealed the successful and functional incorporation of both the peptides within porous polymeric nanolayers as well as surface modifications (i.e. variation in the pore size diameter, surface roughness, and wettability) after Mel, MG or Mel-MG incorporation compared to pNIPAM-co-BA. In vitro testing revealed the impairment of biofilm formation on all the hybrid coatings while testing with S. aureus, E. coli and P. aeruginosa. Moreover, MG was shown to modulate the effect of Mel in the combined Mel-MG extract formulation released via pNIPAM-platforms, thus significantly reducing cancer cell proliferation through apoptosis/necrosis as revealed by flow cytometry analysis performed in vitro on HEK293T, A375, B16F1 and B16F10 cells. To the best of our knowledge, Mel-MG combination entrapped in the pNIPAM-co-BA copolymer has not yet been reported as a new promising candidate with anticancer and antibacterial properties for improved utility in the biomedical field. Mel-MG incorporation compared to pNIPAM-co-BA in in vitro testing revealed the impairment of biofilm formation in all the hybrid formulations.

Niemann-Pick type C1 (NPC1) protein is a multimembrane spanning protein of the lysosome limiting membrane that facilitates intracellular cholesterol and sphingolipid transport. Loss-of-function mutations in the NPC1 protein cause Niemann-Pick disease type C1, a lysosomal storage disorder characterized by the accumulation of cholesterol and sphingolipids within lysosomes. To investigate whether the NPC1 protein could also play a role in the maturation of the endolysosomal pathway, here, we have investigated its role in a lysosome-related organelle, the melanosome. Using a NPC1-KO melanoma cell model, we found that the cellular phenotype of Niemann-Pick disease type C1 is associated with a decreased pigmentation accompanied by low expression of the melanogenic enzyme tyrosinase. We propose that the defective processing and localization of tyrosinase, occurring in the absence of NPC1, is a major determinant of the pigmentation impairment in NPC1-KO cells. Along with tyrosinase, two other pigmentation genes, tyrosinase-related protein 1 and Dopachrome-tautomerase have lower protein levels in NPC1 deficient cells. In contrast with the decrease in pigmentation-related protein expression, we also found a significant intracellular accumulation of mature PMEL17, the structural protein of melanosomes. As opposed to the normal dendritic localization of melanosomes, the disruption of melanosome matrix generation in NPC1 deficient cells causes an accumulation of immature melanosomes adjacent to the plasma membrane. Together with the melanosomal localization of NPC1 in WT cells, these findings suggest that NPC1 is directly involved in tyrosinase transport from the trans-Golgi network to melanosomes and melanosome maturation, indicating a novel function for NPC1.

The impact of the peptide amino acids side-chain modifications on the immunological recognition has been scarcely explored. We investigate here the effect of methionine oxidation on the antigenicity of the melanoma immunodominant peptide 369-YMDGTMSQV-377 (YMD). Using CD8+ T cell activation assays, we found that the antigenicity of the sulfoxide form is higher when compared to the YMD peptide. This is consistent with free energy computations performed on HLA-A∗02:01/YMD/TCR complex showing that this is lowered upon oxidation, paired with a steep increase in order at atomic level. Oxidized YMD forms were identified at the melanoma cell surface by LC-MS/MS analysis. These results demonstrate that methionine oxidation in the antigenic peptides may generate altered peptide ligands with increased antigenicity, and that this oxidation may occur in vivo, opening up the possibility that high-affinity CD8+ T cells might be naturally primed in the course of melanoma progression, as a result of immunosurveillance.

Melanoma is a form of skin cancer that can rapidly invade distant organs. A distinctive feature of melanomas is their pigmentation status, as melanin is present in most skin melanomas, whilst many metastatic tumors could become amelanotic. Besides the obvious malfunction of the key genes of the melanin pathway, the amelanotic tumors could bear a characteristic molecular signature accounting for their aggressivity. Using mass spectrometry-based proteomics we report here a distinctive panel of biomarkers for amelanotic aggressive melanoma that differ from the less invasive pigmented cells. The developed method allows the label-free quantification of proteins identified by LC-MS/MS analysis. We found a set of proteins comprising AHNAK, MYOF, ANXA1, CAPN2, ASPH, EPHA2, THBS1, TGM2, ACTN4 along with proteins involved in cell adhesion/migration (integrins, PLEC, FSCN1, FN1) that are highly expressed in amelanotic melanoma. Accompanying the down regulation of pigmentation specific proteins such as tyrosinase and TYRP1, these biomarkers are highly specific for a type of highly invasive melanoma. Interestingly, the LC-MS/MS proteomics analysis in hypoxia revealed that the abundance of this specific set of proteins found in normoxia was rather unaltered in these conditions. These biomarkers could therefore predict a metastatic behaviour for the amelanotic cells in the early stages of the tumor development and thus serve in melanoma prognostic. Applying this algorithm to related databases including melanoma samples published by independent laboratories/public databases we confirm the specificity of the newly found signatures. Overall, we begin to unravel the molecular alterations in the amelanotic melanoma and how basic proteomics offers insights into how to assess the clinical, pathological and misdiagnosis differences between the main subtypes of melanoma.

Affibody linked to a rigid macrocyclic chelator derived form pyclen-3,9-diacetate (3,9-PC2A) labelled with [52Mn]Mn isotope appears to be a valuable tool for PET-based targeted molecular imaging.

N-glycosylation is a key process for various biological functions like protein folding, maturation and sorting for the conventional secretory compartment, cell-cell communication and immune response. This is usually accomplished by a complex system of mannosidases in which those from class I have an outstanding role, commonly involved in the early protein sorting associated to the Endoplasmic Reticulum (ER) in the N-glycan dependent quality control (ERQC) and ER-associated degradation (ERAD). Although these are vital processes in maintaining cellular homeostasis, large-scale analysis studies for this pool of molecules, further denoted as proteins from the early secretory pathway (ESP), were limited addressed. Here, using a custom workflow employing a combination of glycomics and deglycoproteomics analyses, using lectin affinity and selective Endoglycosidase H (Endo H) digestion, we scrutinize the steady-state oligomannosidic glycoprotein load and delineate ESP fraction in melanoma cells. All of these were assessed by applying our workflow for glycosite relative quantification of both the peptide chain and carbohydrate structure in cells with inhibited activity of class I mannosidases after kifunensine treatment. We found that most of the ESP are transient clients involved in cell communication via extracellular matrix, particularly integrin-mediated communication which adopt Man9 N-glycans in kifunensine-treated cells. Moreover, our results reveal that core-fucosylation is decreased subsequent inhibition of class I mannosidases and this could be explained by a general lower protein level of FUT8, the enzyme responsible for fucosylation. By comparing our data with results obtained following downregulation of a key mannosidase in misfolded protein degradation, we mapped both novel and previously suggested endogenous substrate candidates like PCDH2, HLA-B, LAMB2 or members of the integrin family of proteins such as ITGA1 and ITGA4, thus validating the findings obtained using our workflow regarding accumulation and characterization of ESP transitory members following mannosidase class I inhibition. This workflow and the associated dataset not only allowed us to investigate the oligomannosidic glycoprotein fraction but also to delineate differences mediated at glycosite-level upon kifunensine treatment and outline the potential associated cellular responses.

Considering the valuable information provided by glycosphingolipids as molecular markers and the limited data available for their detection and characterization in patients suffering from Type 2 diabetic kidney disease (DKD), we developed and implemented a superior method based on high-resolution (HR) mass spectrometry (MS) and tandem MS (MS/MS) for the determination of gangliosides in the urine of DKD patients. This study was focused on: (i) testing of the HR MS and MS/MS feasibility and performances in mapping and sequencing of renal gangliosides in Type 2 DM patients; (ii) determination of the changes in the urine gangliosidome of DKD patients in different stages of the disease—normo-, micro-, and macroalbuminuria—in a comparative assay with healthy controls. Due to the high resolution and mass accuracy, the comparative MS screening revealed that the sialylation status of the ganglioside components; their modification by O-acetyl, CH3COO−, O-fucosyl, and O-GalNAc; as well as the composition of the ceramide represent possible markers for early DKD detection, the assessment of disease progression, and follow-up treatment. Moreover, structural investigation by MS/MS demonstrated that GQ1d(d18:1/18:0), GT1α(d18:1/18:0) and GT1b(d18:1/18:0) isomers are associated with macroalbuminuria, meriting further investigation in relation to their role in DKD.

Traditionally fermented foods and beverages are still produced and consumed at a large scale in Romania. They are rich sources for novel lactic acid bacteria with functional properties and with potential application in food industry or health. Lactobacillus helveticus 34.9, isolated from a home-made fermented milk is able to inhibit the growth of other bacteria, such as other lactic acid bacteria, but also strains of Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, and Halobacillus hunanensis, a halobacterium isolated from the degraded wall of a Romanian monastery. L. helveticus 34.9 produces a large bacteriocin (35 KDa), active in a wide pH range, but inactivated by heat and proteinase K treatment. It shares about 20% sequence coverage with helveticin J, as determined by LC–MS analysis. Bacteriocin production was enhanced under stress conditions, especially when combined stresses were applied. Its mode of action and degree of inhibition depended on the concentration and on the indicator strain that was used; L. delbrueckii subsp. bulgaricus LMG 6901T cells from a suspension were killed, but the viability of H. hunanensis 5Hum cells was only reduced to 60%, within 8 h. However, the bacteriocin was able to prevent the bacterial growth of both indicator strains when added to the cultivation medium prior inoculation. Scanning electron microscopy images revealed morphological changes induced by the bacteriocin treatment in both sensitive strains, but more severe in the case of L. delbrueckii subsp. bulgaricus. Due to the broad antibacterial spectrum and its production under various stress conditions, the bacteriocin or the producing strain may find application in health, food and non-food related fields, including in the restoration of historical buildings.

“Drug repositioning” is a modern strategy used to uncover new applications for out-of-date drugs. In this context, nalidixic acid, the first member of the quinolone class with limited use today, has been selected to obtain nine new metal complexes with lanthanide cations (La3+, Sm3+, Eu3+, Gd3+, Tb3+); the experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms, findings that are supported by DFT calculations. The cytotoxic activity of the complexes has been studied using the tumoral cell lines, MDA-MB-231 and LoVo, and a normal cell line, HUVEC. The most active compounds of the series display selective activity against LoVo. Their affinity for DNA and the manner of binding have been tested using UV–Vis spectroscopy and competitive binding studies; our results indicate that major and minor groove binding play a significant role in these interactions. The affinity towards serum proteins has also been evaluated, the complexes displaying higher affinity towards albumin than apotransferrin.

Tailoring extracellular vesicles (EVs) as targeted drug delivery systems to enhance the therapeutic efficacy showed superior advantage over liposomal therapies. Herein, we developed a novel nanotool for targeting B16.F10 murine melanoma, based on EVs stabilized with Polyethylene glycol (PEG) and loaded with doxorubicin (DOX). Small EVs were efficiently enriched from melanoma cells cultured under metabolic stress by ultrafiltration coupled with size exclusion chromatography (UF-SEC) and characterized by size, morphology, and proteome. To reduce their clearance in vivo, EVs were PEGylated and passively loaded with DOX (PEG-EV-DOX). Our data suggested that the low PEG coverage of EVs might still favor EV surface protein interactions with target proteins from intratumor cells, ensuring their use as "Trojan horses" to deliver DOX to the tumor tissue. Moreover, our results showed a superior antitumor activity of PEG-EV-DOX in B16.F10 murine melanoma models in vivo compared to that exerted by clinically applied liposomal DOX in the same tumor model. The PEG-EV-DOX administration in vivo reduced NF-κB activation and increased BAX expression, suggesting better prognosis of EV-based therapy than liposomal DOX treatment. Collectively, our results highlight the promising potential of EVs as optimal tools for systemic delivery of DOX to solid tumors.

Betulinic acid (BA) has been extensively studied in recent years mainly for its antiproliferative and antitumor effect in various types of cancers. Limited data are available regarding the pharmacokinetic profile of BA, particularly its metabolic transformation in vivo. In this study, we present the screening and structural investigations by ESI Orbitrap MS in the negative ion mode and CID MS/MS of phase I and phase II metabolites detected in mouse plasma after the intraperitoneal administration of a nanoemulsion containing BA in SKH 1 female mice. Obtained results indicate that the main phase I metabolic reactions that BA undergoes are monohydroxylation, dihydroxylation, oxidation and hydrogenation, while phase II reactions involved sulfation, glucuronidation and methylation. The fragmentation pathway for BA and its plasma metabolites were elucidated by sequencing of the precursor ions by CID MS MS experiments.

In this study, we developed a high-resolution tandem mass spectrometry (HR MS) approach to assess presumed changes in gangliosidome of a human hippocampus affected by temporal lobe epilepsy (TLE) in comparison with a normal hippocampus. Gangliosides, membrane glycolipids, are particularly diverse and abundant in the human brain, and participate in ion transport and modulation of neuronal excitability. Changes in structural ganglioside pattern potentially linked to TLE molecular pathogenesis have not been explored in detail. Aiming to characterize TLE-specific gangliosidome, we analyzed the native gangliosides purified from a human hippocampal tissue sample affected by TLE and a control hippocampus using HR MS. Marked differences of ganglioside expression were shown in TLE vs. control, particularly with respect to the sialylation degree of components, discovered as a characteristic feature of TLE. Another major finding is the occurrence of tetrasialofucogangliosides in TLE and species modified by either O-acetylation or CH3COO−. Structural analysis by higher-energy collisional dissociation (HCD) MS/MS gave rise to fragmentation patterns implying that the GQ1b (d18:1/18:0) isomer is specifically associated with TLE. Further investigation in a larger sample is needed in order to confirm the discovery of ganglioside structures specifically expressed in human TLE and to provide information on the probable role of gangliosides in the molecular events underlying seizures.

Cognitive impairment and learning ability of the brain are directly linked to synaptic plasticity as measured in changes of long-term potentiation (LTP) and long-term depression (LTD) in animal models of brain diseases. LTD reflects a sustained reduction of the synaptic AMPA receptor content based on targeted clathrin-mediated endocytosis. AMPA receptor endocytosis is initiated by dephosphorylation of Tyr876 on the C-terminus of the AMPAR subunit GluA2. The brain-specific striatal-enriched protein tyrosine phosphatase (STEP) is responsible for this process. To identify new, highly effective inhibitors of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) internalization, we performed structure-based design of peptides able to inhibit STEP-GluA2-CT complex formation. Two short peptide derivatives were found as efficient in vitro inhibitors. Our in vivo experiments evidenced that both peptides restore the memory deficits and display anxiolytic and antidepressant effects in a scopolamine-treated rat model. The interference peptides identified and characterized here represent promising lead compounds for novel cognitive enhancers and/or behavioral modulators.