Abstract
Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disease caused by mutations in the gene encoding protein kinase C γ (PKCγ), a Ca2+- and diacylglycerol-dependent Ser/Thr kinase dominantly expressed in cerebellar Purkinje cells. These mutations impair autoinhibitory constraints to increase the basal activity of the kinase, resulting in deficits in the cerebellum that are not observed upon simple deletion of the gene, and severe ataxia. To better understand the impact of aberrant PKCγ signaling in disease pathology, we developed a knockin murine model of the SCA14 mutation ΔF48 in PKCγ. This fully penetrant mutation is severe in humans and is mechanistically informative, as it has high basal activity but is unresponsive to agonist stimulation. Genetic, behavioral, and molecular testing revealed that ΔF48 PKCγ mice have ataxia-related phenotypes and an altered cerebellar phosphoproteome driven primarily by enhanced Ca2+/calmodulin-dependent kinase 2 signaling, effects that were more severe in male mice. Analysis of existing human data revealed that SCA14 has a significantly earlier age of onset for males compared with females. Data from this clinically relevant mutation suggested that enhanced basal activity of PKCγ is sufficient to cause ataxia and that treatment strategies to modulate aberrant PKCγ may be particularly beneficial in males.
Authors
Sarah A. Wolfe, Yuliang Ma, Tomer M. Yaron-Barir, Carly Chang, Caila A. Pilo, Majid Ghassemian, Amanda J. Roberts, Sang Ryeul Lee, Benjamin A. Henson, Kristen Jepsen, Jared L. Johnson, Lewis C. Cantley, Susan S. Taylor, George Gorrie, Alexandra C. Newton
Abstract
Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by mutations in the survival motor neuron 1 (SMN1) gene leading to decreased SMN protein levels and motor neuron dysfunction. SMN-restoring therapies offer clinical benefit, but the downstream molecular consequences of SMN reduction remain incompletely understood. SMN deficiency resulted in downregulation of kinesin heavy chain isoform 5A (KIF5A) in human neurons and in a mouse model of SMA. SMN associated with KIF5A mRNA and contributed to its stability. Reduced SMN levels impaired axon regeneration, which was rescued by KIF5A overexpression. Because KIF5A has also been connected to ALS, these findings provide evidence of a molecular link between SMA and ALS pathophysiology, highlighting KIF5A as an SMN-regulated factor. Our findings suggest that SMN-independent interventions targeting KIF5A could represent a complementary therapeutic approach for SMA and other motor neuron diseases.
Authors
Tetsuya Akiyama, Yi Zeng, Caiwei Guo, Olivia Gautier, Lauren Koepke, Heankel Lyons, Elana Molotsky, Juliane S. Bombosch, Odilia Sianto, Jay P. Ross, Phuong Hoang, Luke Zhao, Cole Spencer, Charlotte J. Sumner, Michelle Monje, John W. Day, Aaron D. Gitler
Abstract
Dedifferentiated liposarcoma (DDLS), myxofibrosarcoma (MFS), and undifferentiated pleomorphic sarcoma (UPS) are the most common types of genetically complex sarcoma. There is an urgent need to develop effective targeted therapy for these deadly sarcoma types. Despite their genetic complexity, these sarcomas share genomic alterations causing PI3K/Akt/mTOR and MAPK pathway activation, and both pathways control translation mediated by the RNA helicase eIF4A. We therefore investigated eIF4A inhibition as a therapeutic strategy. The eIF4A inhibitor CR-1-31B effectively suppressed tumor growth and induced apoptosis in DDLS, MFS, and UPS patient–derived cell lines and mouse xenografts. Transcriptome-scale ribosome footprinting identified eIF4A-dependent mRNAs such as the Hippo pathway transcriptional coactivators YAP1 (YAP) and WWTR1 (TAZ). Combined knockdown of YAP and TAZ induced apoptosis in DDLS, MFS, and UPS cell lines, and their ectopic expression partially rescued cells from apoptosis induced by CR-1-31B. Genomic analysis of patient tumors revealed that YAP and WWTR1 were frequently amplified or gained in DDLS, MFS, and UPS and were associated with worse clinical outcomes. Together, our findings identify a strategy for targeting the Hippo pathway in incurable forms of sarcoma based on inhibition of eIF4A-dependent translation of the key oncogenic transcription factors YAP and TAZ.
Authors
Young-Mi Kim, Prathibha Mohan, Urmila Sehrawat, Evan Seffar, Rafaela Muniz De Queiroz, Kalyani Chadalavada, Nikita Persaud, Tomoyo Okada, Anirudh Kulkarni, Jianan Lin, Nathalie Lailler, Shaleigh Smith, Bhumika Jadeja, Nicholas D. Socci, Zhengqing Ouyang, Hans-Guido Wendel, Samuel Singer
Abstract
We investigated whether destroying malignant cells and the associated tumor microenvironment (TME) by focal gene therapy would broaden immune checkpoint inhibitor (ICI) effectiveness. We show that ICI antitumor activity against syngeneic (murine) triple-negative breast cancer (TNBC) was augmented when a therapeutic transgene (purine nucleoside phosphorylase, referred to here as E. coli PNP) was used to cleave fludarabine (2-fluoro-arabinofuranosyl adenine) to the anticancer purine base, 2-fluoroadenine (F-Ade). We also established strong repression of anatomically distant, non-PNP-expressing tumors being treated by the same strategy. TNBC cytoreduction was associated with decreased intratumoral PD1+ Tregs, increased granzyme B+ NK cells, elevated MKI67+ T8 cells, and rapid immune clearance. Because F-Ade works by a mechanism that destroys quiescent neoplastic and supporting cells in the microenvironment, and since resistance to ICIs depends upon an intact TME, tumor killing by this approach offers a means to sensitize refractory malignancies to immune ablation and points to broad applicability against numerous cancer subtypes.
Authors
Regina Rab, Jeong S. Hong, Brendan L.C. Kinney, Nicole C. Schmitt, William B. Parker, Adrianna Westbrook, Kelsey B. Bennion, Mandy L. Ford, Douglas H. Weitzel, Paula L. Miliani de Marval, Eric J. Sorscher, Annette Ehrhardt
Abstract
Hyperglycemia is a principal driver of β cell failure and multiple-organ complications in diabetes. Chronic exposure to hyperglycemia overstimulates mTORC1, disrupting glucose metabolism and promoting ER stress, oxidative stress, and inflammation; however, the upstream metabolic signal(s) linking glucose to mTORC1 activation remains unclear. Here, we identified glucosamine as a key metabolite connecting elevated glucose to mTORC1 signaling in pancreatic islets and kidney, both major targets of hyperglycemic damage. Using 13C6-glucose metabolic labeling in diabetic rodents treated with or without the SGLT2 inhibitor dapagliflozin or insulin, combined with targeted metabolomics and metabolic flux analysis, we found that tissue glucose concentrations strongly correlated with glucosamine. A similar correlation with plasma glucose was conserved in humans with or without type 2 diabetes, and inversely associated with β cell function. In vitro, low-dose glucosamine stimulated mTORC1 in islets and kidney proximal tubule cells in an O-GlcNAcylation–dependent manner. Broad phosphoproteomics and transcriptomics analyses in β cells showed that glucosamine activated mTORC1-regulating pathways, induced oxidative stress, ER stress, and dedifferentiation. Genetic inhibition of β cell mTORC1 via heterozygous Raptor knockout, as well as pharmacologic inhibition of the glucosamine/mTORC1 axis through SGLT2 inhibition, alleviated β cell stress, improved glycemic control, and restored β cell function. These findings identified the glucosamine/mTORC1 pathway as an important mediator of β cell and kidney dysfunction in diabetes.
Authors
Yael Riahi, Aviram Kogot-Levin, Ziv Teselpapa, Elisheva Zemelman, Fatema Gamal, Tamar Cohen, Abed Nasereddin, Idit Shiff, Ifat Abramovich, Bella Agranovich, Dana Avrahami, Liad Hinden, Erol Cerasi, Daljeet Kaur, Lihi Grinberg, Ron Piran, Joseph Tam, Ernesto Bernal-Mizrachi, Erez Dror, Gil Leibowitz
Abstract
Small-conductance Ca2+-activated K+ (SK) channels regulate neuronal excitability and act as a feedback mechanism to limit firing during sustained stimulation. In the present study, we demonstrated that SK2 plays an important role in the control of bladder function and visceral pain processing. SK2 channels are expressed in bladder-innervating afferent neurons, and ablation of this subunit results in elevated afferent firing rates in response to physiological levels of bladder distension, supporting a role for SK2 in modulating mechanosensory excitability. Mice overexpressing SK2 exhibit increased bladder capacity and reduced voiding frequency. Furthermore, overexpression of SK2 prevents the onset of pelvic mechanical allodynia and attenuates the exaggerated visceromotor response to bladder distension seen in wild-type mice with chemical cystitis. Thus, SK2 may be a promising target for treating overactive bladder and pain originating from the urinary bladder and other pelvic organs.
Authors
Guadalupe Manrique-Maldonado, Xuejiao Sun, Allison L. Marciszyn, Nicolas Montalbetti, Marcelo D. Carattino
Abstract
Brain metastases (BrMs) occur in approximately 30% of cancer patients, causing nearly one-fifth of cancer deaths. While immune checkpoint inhibitors (ICIs) benefit some BrM patients, responses remain highly variable. This variability partly reflects distinct histopathological growth patterns that include minimally invasive (MI) and highly invasive (HI) brain BrMs. Here we show that MI BrMs exhibit robust immune infiltration, whereas HI lesions are immunosuppressed. However, histological differentiation between MI and HI can be challenging because of subjective margin assessment. Here, using highly multiplexed spatial proteomics on 119 tumor sections from 46 patients with BrMs, we identify CHI3L1 as a key mediator of the immunosuppressive microenvironment in HI BrMs. In preclinical models, genetic deletion of CHI3L1 converts immune-cold metastases into lymphocyte-rich, ICI-responsive lesions infiltrated by granzyme B+ CD8+ T cells. In BrM patients treated with ICI, immunohistochemical quantification of CHI3L1 expression was a stronger predictor of ICI response than traditional MI/HI classification. Thus, CHI3L1 represents a promising biomarker and therapeutic target for BrMs.
Authors
Sarah M. Maritan, Elham Karimi, Matthew Dankner, Aldo Hernandez-Corchado, Miranda W. Yu, Matthew G. Annis, Yashar Aghazadeh Habashi, Morteza Rezanejad, Bridget Liu, Nebras Koudieh, Emilie Pichette, Parvaneh Fallah, Benoit Fiset, Yuhong Wei, Ali Nehme, Chun Geun Lee, Jack A. Elias, Morag Park, Yasser Riazalhosseini, Hamed Najafabadi, Kevin Petrecca, Marie-Christine Guiot, Daniela F. Quail, Logan A. Walsh, Peter M. Siegel
Abstract
In multiple sclerosis (MS) lesions, CD8 T cells outnumber CD4 T cells, suggesting that they contribute to MS pathology. However, little is known about the role of CD8 T cells in MS, partly due to the prevalent use of experimental autoimmune encephalomyelitis (EAE) models mediated by CD4 T cells, which have limited involvement of CD8 T cells. Importantly, MS and EAE differ in both their distribution of CNS lesions and neurologic deficits, indicating differences in CNS inflammation. MS lesions are more commonly found in the brain, whereas EAE lesions are more frequent in the spinal cord. Additionally, neurologic deficits in MS rarely parallel the ascending paralysis typical for CD4 T cell–mediated EAE (CD4-EAE). In contrast, CD8-EAE models suggest that CD8 T cells preferentially cause brain inflammation; however, little is known about how brain and spinal cord inflammation may differ, or how CD8 T cells contribute to these differences. We have established an adoptive CD8-EAE mouse model characterized by brain-centered inflammation, ataxia, and weight loss. CNS inflammation in the brain and spinal cord differed in immune cell numbers, cellular composition, and inflammatory signatures. CD8-EAE could be suppressed by blocking IFN-γ, and exacerbated by blocking PD-1, with concomitant changes in the numbers of CNS-infiltrating monocytes. Most CD8 T cells in the CNS were CD11c+, suggesting that they are the pathogenic subset. We describe a robust CD8-EAE model, identify differences between brain and spinal cord inflammation, and characterize mechanisms that control CD8 T cell–mediated neuroinflammation, thereby furthering understanding of EAE and MS.
Authors
Daniel Hwang, Gholamreza Azizi, Larissa Lumi Watanabe Ishikawa, Maryam Seyedsadr, Arin Cox, Soohwa Jang, Ezgi Kasimoglu, Abdolmohamad Rostami, Guang-Xian Zhang, Bogoljub Ciric
Abstract
Bladder cancer (BCa) mortality is mainly driven by metastatic dissemination and an immunosuppressive tumor microenvironment. Here, we identify ELN (tropoelastin), an extracellular matrix protein abundantly secreted by cancer-associated fibroblasts (CAFs), as a critical determinant of these processes and a marker of poor prognosis. ELN promotes epithelial-mesenchymal transition (EMT), facilitates lymphatic spread, and induces immune dysfunction characterized by macrophage polarization toward an M2 phenotype and T cell exhaustion. Mechanistically, ELN functions as a binding partner of TGF-β receptor 2 (TGFBR2), thereby triggering SMAD2/3-dependent TGF-β1 secretion and establishing a feed forward signaling loop. This ELN/TGFBR2/TGF-β1 axis amplifies metastatic capacity and immunosuppressive signaling, ultimately accelerating disease progression and diminishing responsiveness to immune checkpoint blockade. Functional studies in BCa organoids and murine models demonstrated that pharmacologic blockade of the ELN-TGFBR2 interaction effectively suppressed tumor metastasis and restored antitumor immunity. Collectively, our findings establish ELN as a CAF-derived driver of metastasis and immune evasion in BCa. Targeting the ELN-TGFBR2 interaction offers a promising therapeutic strategy to limit metastatic progression and enhance the efficacy of immunotherapy in this lethal disease.
Authors
Wentao Xu, Jia Gao, Shanshan Wu, Jianshang Huang, Chenchen An, Chonggui Jiang, Nianping Liu, Chen Cheng, Zihan Wang, Zijian Dong, Yuchen Xu, Jun Zhou, Hanren Dai, Xiaolei Li, Honghai Xu, Songyun Zhao, Qianwen Fan, Yang Li, Ying Dai, Li Zuo, Hua Wang
Abstract
Preclinical studies suggest beneficial effects of GLP-1 agonists in pulmonary arterial hypertension (PAH). This first-in-disease study evaluated acute hemodynamic effects of GLP-1 agonist, exenatide administered i.v. in patients with idiopathic PAH and CTEPH as well as in a PAH rodent model. Seventeen patients (9 idiopathic PAH) received an exenatide infusion during right heart catheterization, which included multisite sampling for circulating metabolites. Acute effects of exenatide were also assessed by cardiac magnetic resonance imaging in monocrotaline (MCT) PAH and control rats. In the clinical study, exenatide was well tolerated, reduced mean pulmonary artery pressure (45 ± 15 mmHg versus 40 ± 18 mmHg), and improved cardiac index (2.1 ± 0.6 L/min versus 2.4 ± 0.9 L/min/m2) and pulmonary vascular resistance (7.8 ± 8.0 WU versus 5.9 ± 5.0 WU) across all patients. Right ventricular (RV) contractility and afterload improved in a subset of patients undergoing pressure-volume measurements. In an exploratory metabolomics analysis, 47 metabolite levels changed after exenatide infusion, predominantly in free fatty acid pathways. Six metabolites with prognostic relevance in PAH within myocardial glycolytic and lipid oxidation pathways were also altered after exenatide. In MCT rats, exenatide improved RV stroke-volume, RV ejection fraction, and RV-arterial coupling. These findings support the further evaluation of exenatide within chronic studies as a potentially novel pulmonary vasodilator therapy.
Authors
Chinthaka B. Samaranayake, Marili Niglas, Nicoleta Baxan, Alexander Kempny, Ali Ashek, Michael Gatzoulis, Laura C. Price, Konstantinos Dimopoulos, Martin R. Wilkins, Stephen Wort, Christopher J. Rhodes, Lan Zhao, Colm McCabe
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