Biology subjects

Kamenecka, T. M.

Publications and source records attributed to Kamenecka, T. M..

11 recordsLinked to original sources

bioRxiv2026

Selective Glucocorticoid Receptor Modulators of Immune Checkpoint Function

Glucocorticoids (GCs) coordinate immunity, inflammation, and metabolism through allosteric regulation of the glucocorticoid receptor (GR) transcription factor. GCs are indispensable anti-inflammatory drugs yet linking specific ligand-receptor structural states to specific biological outcomes has remained a major barrier to designing safer, more selective therapies. Using structure-based design, we developed selective glucocorticoid receptor modulators (SGRMs) of immune function by extending a steroidal scaffold from the ligand-binding pocket into an adjacent solvent channel. These SGRMs suppressed T cell pro-inflammatory cytokines and promoted differentiation of memory precursor T cells while showing minimal induction of M2 macrophage polarization or T cell checkpoint proteins PD-1 and CTLA-4, all key targets of immunotherapy. Molecular dynamics simulations revealed that solvent-channel substituents function as a lever arm to drive dynamic oscillations in the steroid core, thereby allosterically tuning GR activity states. Systematic perturbation of immune cells with a graded series of ligands enabled a ligand perturbation with machine learning (LPML) framework to map coregulated responses across cell types and identified effector T cell gene networks tightly coupled with immune checkpoint induction. This approach outlines a general strategy for decoding the logic of allosteric drug action, enabling the rational design of SGRMs with tailored immunomodulatory profiles.

systems biology↗

bioRxiv2025

Structural basis of PPARγ-mediated transcriptional repression by the covalent inverse agonist FX-909

Hyperactivation of peroxisome proliferator-activated receptor gamma (PPAR{gamma})-mediated transcription promotes tumor growth in urothelial (bladder) cancer, which can be inhibited by pharmacological compounds that repress PPAR{gamma} activity. FX-909 is a covalent PPAR{gamma} inverse agonist currently in phase 1 clinical trials for advanced solid malignancies including muscle-invasive bladder cancer. Here, we compared the mechanism of action of FX-909 to other covalent inverse agonists including T0070907, originally reported more than 20 years ago and misclassified as an antagonist, and two recently reported improved covalent inverse agonist analogs, SR33068 and BAY-4931. Functional profiling and NMR studies reveal that FX-909 displays improved corepressor-selective inverse agonism and better stabilizes a transcriptionally repressive PPAR{gamma} LBD conformation compared to T0070907. The crystal structure of PPAR{gamma} LBD cobound to FX-909 and NCoR1 corepressor peptide reveals a repressive conformation shared by other covalent inverse agonists. These findings build on recent studies highlighting the pharmacological significance and clinical relevance of transcriptionally repressive PPAR{gamma} inverse agonists.

biophysics↗

bioRxiv2025

Towards a unified molecular mechanism for ligand-dependent activation of NR4A-RXR heterodimers

A subset of nuclear receptors (NRs) function as permissive heterodimers with retinoid X receptor (RXR), defined by transcriptional activation in response to RXR agonist ligands. Permissive NR-RXR activation is generally understood to operate through a classical pharmacological mechanism in which RXR agonist binding enhances coactivator recruitment to the heterodimer. However, we previously demonstrated that transcriptional activation of permissive Nurr1-RXR (NR4A2-NR2B1) heterodimers by an RXR ligand set, which included pharmacological RXR agonists and selective Nurr1-RXR agonists that function as antagonists of RXR homodimers, is explained by a non-classical activation mechanism involving ligand-binding domain (LBD) heterodimer dissociation (Yu et al., 2023). Here, we extend mechanistic ligand profiling of the same RXR ligand set to the evolutionarily related Nur77-RXR{gamma} (NR4A1-NR2B3) heterodimer. Biochemical and NMR protein-protein interaction profiling, together with cellular transcription studies, indicate that activation of Nur77-RXR{gamma} transcription by the RXR ligand set, which lacks selective Nur77-RXR{gamma} agonists, is consistent with contributions from both classical pharmacological activation and LBD heterodimer dissociation. However, reanalysis of our previously published data for Nurr1-RXR revealed that inclusion of selective Nurr1-RXR agonists was essential for elucidating the LBD heterodimer dissociation mechanism. Together, our findings highlight the importance of using a more functionally diverse RXR ligand set to define the mechanism of Nur77-RXR{gamma} activation and to further evaluate whether LBD heterodimer dissociation represents a shared activation mechanism among NR4A-RXR heterodimers relevant to neurodegenerative and inflammatory diseases.

biochemistry↗

bioRxiv2025

Shifting the PPARγ conformational ensemble towards a transcriptionally repressive state improves covalent inhibitor efficacy

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR{gamma}) regulates transcription in response to ligand binding at an orthosteric pocket within the ligand-binding domain (LBD). We previously showed that two covalent ligands, T0070907 and GW9662--extensively used as PPAR{gamma} inhibitors to assess off-target activity--weaken but do not completely block ligand binding via an allosteric mechanism associated with pharmacological inverse agonism (Shang et al., 2024). These covalent inhibitors shift the LBD towards a repressive conformation, where the activation function-2 (AF-2) helix 12 occupies the orthosteric pocket, competing with orthosteric ligand binding. Here, we provide additional support for this allosteric mechanism using two covalent inverse agonists, SR33065 and SR36708, which better stabilize the repressive LBD conformation and are more effective inhibitors of--but also do not completely inhibit--ligand cobinding. Furthermore, we show that ligand cobinding can occur with a previously reported PPAR{gamma} dual-site covalent inhibitor, SR16832, which appears to weaken ligand binding through a direct mechanism independent of the allosteric mechanism. These findings underscore the complex nature of the PPAR{gamma} LBD conformational ensemble and highlight the need to develop alternative methods for designing more effective covalent inhibitors.

biochemistry↗

bioRxiv2024

Development of novel flavonoid senolytics through phenotypic drug screening and drug design

Accumulation of senescent cells drives aging and age-related diseases. Senolytics, which selectively kill senescent cells, offer a promising approach for treating many age-related diseases. Using a senescent cell-based phenotypic drug discovery approach that combines drug screening and drug design, we developed two novel flavonoid senolytics, SR29384 and SR31133, derived from the senolytic fisetin. These compounds demonstrated enhanced senolytic activities, effectively eliminating multiple senescent cell types, reducing tissue senescence in vivo, and extending healthspan in a mouse model of accelerated aging. Mechanistic studies utilizing RNA-Seq, machine learning, network pharmacology, and computational simulation suggest that these novel flavonoid senolytics target PARP1, BCL-xL, and CDK2 to induce selective senescent cell death. This phenotype-based discovery of novel flavonoid senolytics, coupled with mechanistic insights, represents a key advancement in developing next-generation senolyticss with potential clinical applications in treating aging and age-related diseases.

cell biology↗

bioRxiv2024

Development of Clinically Viable Non-Muscle Myosin II Small Molecule Inhibitors with Broad Therapeutic Potential

Non-muscle myosin II (NMII), a molecular motor that regulates critical processes such as cytokinesis and neuronal synaptic plasticity, has substantial therapeutic potential. However, translating this potential to in vivo use has been hampered by the lack of selective tools. The most prototypical non-selective inhibitor, blebbistatin inactivates both NMII and cardiac myosin II (CMII), a key regulator of heart function. Using rational drug design, we developed a series of NMII inhibitors that improve tolerability by selectively targeting NMII over CMII, including MT-228, which has excellent properties such as high brain penetration and efficacy in preclinical models of stimulant use disorder, which has no current FDA-approved therapies. The structure of MT-228 bound to myosin II provides insight into its 17-fold selectivity for NMII over CMII. MT-228s broad therapeutic window opens the door to new disease treatments and provides valuable tools for the scientific community, along with promising leads for future medication development. HighlightsO_LIResearch suggests numerous indications, from axon regeneration and cancer, would benefit from a small molecule inhibitor of non-muscle myosin II, a molecular motor that regulates the actin cytoskeleton. C_LIO_LICurrent chemical probe options are very limited and lack sufficient safety for in vivo C_LIO_LIstudies, which we show is primarily due to potent inhibition of cardiac myosin II. C_LIO_LIRational design that focused on improving target selectivity over the pan-myosin II inhibitor, blebbistatin, led to the identification of MT-228, a small molecule inhibitor with a wide therapeutic window. C_LIO_LIHigh-resolution structure of MT-228 bound to myosin II reveals that selectivity results from a different positioning compared to blebbistatin and an important sequence difference between cardiac and non-muscle myosin II in the inhibitor binding pocket. C_LIO_LIA single administration of MT-228 shows long-lasting efficacy in animal models of stimulant use disorder, a current unmet and rapidly escalating need with no FDA-approved treatments. C_LI

cell biology↗

bioRxiv2024

MT-125 Inhibits Non-Muscle Myosin IIA and IIB, Synergizes with Oncogenic Kinase Inhibitors, and Prolongs Survival in Glioblastoma

We have identified a NMIIA and IIB-specific small molecule inhibitor, MT-125, and have studied its effects in GBM. MT-125 has high brain penetrance and retention and an excellent safety profile; blocks GBM invasion and cytokinesis, consistent with the known roles of NMII; and prolongs survival as a single agent in murine GBM models. MT-125 increases signaling along both the PDGFR- and MAPK-driven pathways through a mechanism that involves the upregulation of reactive oxygen species, and it synergizes with FDA-approved PDGFR and mTOR inhibitors in vitro. Combining MT-125 with sunitinib, a PDGFR inhibitor, or paxalisib, a combined PI3 Kinase/mTOR inhibitor significantly improves survival in orthotopic GBM models over either drug alone, and in the case of sunitinib, markedly prolongs survival in [~]40% of mice. Our results provide a powerful rationale for developing NMII targeting strategies to treat cancer and demonstrate that MT-125 has strong clinical potential for the treatment of GBM. HighlightsO_LIMT-125 is a highly specific small molecule inhibitor of non-muscle myosin IIA and IIB, is well-tolerated, and achieves therapeutic concentrations in the brain with systemic dosing. C_LIO_LITreating preclinical models of glioblastoma with MT-125 produces durable improvements in survival. C_LIO_LIMT-125 stimulates PDGFR- and MAPK-driven signaling in glioblastoma and increases dependency on these pathways. C_LIO_LICombining MT-125 with an FDA-approved PDGFR inhibitor in a mouse GBM model synergizes to improve median survival over either drug alone, and produces tumor free, prolonged survival in over 40% of mice. C_LI

cancer biology↗

bioRxiv2021

Conformational Changes of RORγ During Response Element Recognition and Coregulator Engagement.

The retinoic acid receptor-related orphan receptor {gamma} (ROR{gamma}) is a ligand-dependent transcription factor of the nuclear receptor super family that underpins metabolic activity, immune function, and cancer progression. Despite being a valuable drug target in health and disease, our understanding of the ligand-dependent activities of ROR{gamma} is far from complete. Like most nuclear receptors, ROR{gamma} must recruit coregulatory protein to enact the ROR{gamma} target gene program. To date, a majority of structural studies have been focused exclusively on the ROR{gamma} ligand-binding domain and the ligand-dependent recruitment of small peptide segments of coregulators. Herein, we examine the ligand-dependent assembly of full length ROR{gamma}:coregulator complexes on cognate DNA response elements using structural proteomics and small angle x-ray scattering. The results from our studies suggest that ROR{gamma} becomes elongated upon DNA recognition, preventing long range interdomain crosstalk. We also determined that the DNA binding domain adopts a sequence-specific conformation, and that coregulatory proteins may be able to sense the ligand- and DNA-bound status of ROR{gamma}. We propose a model where ligand-dependent coregulator recruitment may be influenced by the sequence of the DNA to which ROR{gamma} is bound. Overall, the efforts described herein will illuminate important aspects of full length ROR{gamma} and monomeric orphan nuclear receptor target gene regulation through DNA-dependent conformational changes. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/445650v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1f0a067org.highwire.dtl.DTLVardef@b2e9f6org.highwire.dtl.DTLVardef@1e15d5org.highwire.dtl.DTLVardef@12b8546_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

Discovery of a Novel, Selective and Short-Acting Skeletal Myosin II Inhibitor

Myosin IIs, actin-based motors that utilize the chemical energy of ATP to generate force, have potential as therapeutic targets. Their heavy chains differentiate the family into muscle (skeletal [SkMII], cardiac, smooth) and nonmuscle myosin IIs. Despite therapeutic potential for muscle disorders, no SkMII-specific inhibitor has been reported and characterized. Here we present the discovery, synthesis and characterization of "skeletostatins", novel derivatives of the pan-myosin II inhibitor blebbistatin, with selectivity within the myosin IIs for SkMII. In addition, the skeletostatins bear improved potency, solubility and photostability, without cytotoxicity. Based on its optimal in vitro profile, Skeletostatin 1s in vivo tolerability, efficacy and pharmacokinetics were determined. Skeletostatin 1 was well-tolerated in mice, impaired motor performance, and had an excellent muscle to plasma ratio. Skeletostatins are useful probes for basic research and a strong starting point for drug development.

pharmacology and toxicology↗

bioRxiv2020

A Simple and Robust Cell Based Assay for the Discovery of Novel Cytokinesis Inhibitors

Cytokinesis is the last step of mitotic cell division that separates the cytoplasm of dividing cells. Small molecule inhibitors targeting either the elements of the regulatory pathways controlling cytokinesis, or the terminal effectors have been of interest as potential drug candidates for the treatment of various diseases. Here we have developed a cell-based assay for the discovery of novel cytokinesis inhibitors. The assay is performed in a 96-well plate format in 48 hours. Living cells, nuclei and nuclei of dead cells are revealed by a single staining step with three fluorescent dyes, followed by live cell imaging using an automated fluorescence microscope. The primary signal is the nuclei-to-cell ratio (NCR). In the presence of cytokinesis inhibitors, this ratio is expected to increase over time, as the ratio of multinucleated cells increases in the population. Cytotoxicity is quantified as the ratio of dead nuclei to total nuclei. A screening window coefficient (Z) of 0.65 indicates that the assay is suitable for screening purposes, as the positive and negative controls are well-separated. EC50 values for four compounds can be reliably determined in a single 96-well plate by using only six different compound concentrations. An excellent test-retest reliability (R2=0.998) was found for EC50 values covering a [~]1500-fold range of potencies. The robustness, simplicity and flexibility of the assay is demonstrated here by using modulators of actin dynamics with different mechanisms of action (jasplakinolide, cytochalasin D and swinholide A) and derivatives of the nonmuscle myosin II inhibitor blebbistatin.

cell biology↗

bioRxiv2019

Methamphetamine learning induces persistent nonmuscle myosin II-dependent spine motility in the basolateral amygdala

Nonmuscle myosin II inhibition (NMIIi) in the basolateral amygdala (BLA) selectively disrupts memories associated with methamphetamine (METH) days after learning, without retrieval. However, the molecular mechanisms underlying this selective vulnerability remain poorly understood. A known function of NMII is to transiently activate dendritic spine actin dynamics with learning. Therefore, we hypothesized that METH-associated learning perpetuates NMII-driven actin dynamics in dendritic spines, leading to an extended window of vulnerability for memory disruption. Two-photon imaging of actin-mediated spine motility in neurons from memory-related structures, BLA and CA1, revealed a persistent increase in spine motility after METH-associated learning that was restricted to BLA neurons. METH-induced changes to BLA spine dynamics were reversed by a single systemic injection of an NMII inhibitor. Thus, a perpetual form of NMII-driven spine actin dynamics in BLA neurons may contribute to the unique susceptibility of METH-associated memories.

neuroscience↗