Cell biology
Abstract
Mutations in LMNA, encoding nuclear lamina protein Lamin A/C, cause premature aging disorders, most notably Hutchinson-Gilford Progeria Syndrome. Despite obvious skull abnormalities in progeroid patients, the disease-causing mechanism remains elusive. The L648R single amino acid substitution blocks prelamin A maturation in mice, modeling a unique human patient. Here, we describe skull deformities in premature aging caused by aberrant suture fusion resembling those of patients with craniosynostosis. Further examinations identify prelamin A accumulation causatively linked to multiple suture synostoses in low bone density. This etiology is distinct from conventional suture fusion mediated by excessive ossification. In addition, the mutation disrupts skeletal stem cell stemness and subsequent stem cell-mediated proliferation and differentiation in osteogenesis. Intrasutural bones present in progeroid patients are highly reminiscent of synostosis caused by stem cell exhaustion. Comparative gene expression profiling further reveals cytoskeletal dynamics associated with skeletogenic cell aging and suture patency in mice and humans. Functional studies demonstrate that abnormal structures of progeric nuclei caused by prelamin A accumulation affect cytoskeleton organization and nucleoskeleton assembly essential for craniofacial skeletogenesis. Pharmacogenetic analyses indicate alleviation of osteogenic defects via actin polymerization. Our findings provide compelling evidence for nuclear and cytoskeletal defects, mediating stem cell-associated osteogenic deformities in progeroid disorders.
Authors
Kai Li, Trunee Hsu, Hitoshi Uchida, Tingxi Wu, Susan Michaelis, Howard J. Worman, Wei Hsu
Abstract
The survival of patients with acute myelogenous leukemia (AML) carrying mutations in TP53 is dismal. We report the results of a detailed characterization of responses to treatment ex vivo with the MDM2 inhibitor MI219, a p53 protein stabilizer, in AML blasts from 165 patients focusing analyses on TP53 wildtype (WT) patients. In total 33% of AML were absolute resistant to MDM2 inhibitor induced apoptosis, of which 45% carried TP53 mutation and 55% were TP53 WT. We conducted array-based expression profiling of ten resistant and ten sensitive AML cases with WT TP53 status, respectively, at baseline and after 2h and 6h of MDM2 inhibitor treatment. While sensitive cases showed the induction of classical TP53 response genes, this was absent or attenuated in resistant cases. In addition, the sensitive and resistant AML samples at baseline profoundly differed in the expression of inflammation-related and mitochondrial genes. No TP53 mutated AML patient survived. The 4-year survival of AML with defective MDM2 inhibitor induced TP53-mediated apoptosis despite WT TP53 was dismal at 19% when NPM1 was co-mutated and 6% when NPM1 was WT. In summary, we identified prevalent multi-causal defects in TP53-mediated apoptosis in AML resulting in extremely poor patient survival.
Authors
Josephine Dubois, Anthony Palmer, Darren King, Mohamed Rizk, Karan Bedi, Kerby A. Shedden, Sami N. Malek
Abstract
Psoriasis is a chronic inflammatory dermatosis characterized by pathological keratinocyte hyperproliferation and dysregulated immune activation. While ubiquitin-specific peptidase 16 (USP16) has been implicated in modulating multiple cellular signaling pathways, its functional role in psoriatic pathogenesis remains poorly understood. Our investigation revealed pronounced upregulation of USP16 expression in psoriatic epidermis compared to normal controls. Keratinocyte-specific USP16 knockdown demonstrated remarkable therapeutic efficacy, significantly ameliorating characteristic psoriatic phenotypes including epidermal hyperplasia and inflammatory infiltration. RNA sequencing analysis showed that USP16 has substantial effects on cell cycle transition and keratinocytes proliferation. Through KEGG analysis, it was found that USP16 primarily regulates the NLRP3 signaling pathway, leading to enhanced cell proliferation and inflammation. Mechanically, USP16 directly binds to the NLRP3 protein to eliminate K48 ubiquitination modification, enhancing the stability of the NLRP3 protein, activating inflammasome activity. Further studies showed that the therapeutic effect of reducing USP16 on psoriasis progression were counteracted by an NLRP3 activator and keratinocyte-specific NLRP3 overexpression adenovirus. Collectively, these results shed light on how USP16 promotes NLRP3 signaling in keratinocytes, exacerbating psoriasis development. This positive regulation highlights the potential of USP16 as a therapeutic target for psoriasis.
Authors
Nan Wang, Fangqian Guan, Yifan Lin, Bohao Sun, Jindan Dai, Xiejun Xu, Weibo Tang, Yanhua Ren, Xuliang Huang, Wenjie Gao, Xixi Chen, Litai Jin, Weitao Cong, Zhongxin Zhu
Abstract
We provide evidence that human and murine SLFN5 proteins are modulators of Type I IFN responses and the immune response in pancreatic cancer. Blocking expression of Slfn5 in PDAC enhances IFN-responses, suppresses tumor growth, and prolongs survival in immunocompetent mice. Notably, immunophenotypic analysis reveals a reduction in tumor-associated macrophages (TAMs) alongside an increase in tumor infiltrating effector cells in tumors over time. These findings implicate SLFN5 acts as an intracellular immune checkpoint and identify it as a unique therapeutic target for the development of therapies for PDAC and possibly other malignancies.
Authors
Mariafausta Fischietti, Markella Zannikou, Elspeth M. Beauchamp, Diana Saleiro, Aneta H. Baran, Briana N. Hryhorysak, Jamie N. Guillen Magaña, Emely Lopez Fajardo, Gavin T. Blyth, Brandyn A. Castro, Jason M. Miska, Catalina Lee-Chang, Priyam Patel, Elizabeth T. Bartom, Masha Kocherginsky, Frank Eckerdt, Leonidas C. Platanias
Abstract
Cachexia is a debilitating syndrome characterized by progressive skeletal muscle wasting, commonly affecting cancer patients, particularly those with pancreatic cancer. Despite its clinical significance, the molecular mechanisms underlying cancer cachexia remain poorly understood. In this study, we utilized single-nucleus RNA sequencing (snRNA-seq) and bulk RNA-seq, complemented by biochemical and histological analyses, to investigate molecular alterations in the skeletal muscle of the KPC mouse model of pancreatic cancer cachexia. Our findings demonstrated that KPC tumor growth induced myofiber-specific changes in the expression of genes involved in proteolytic pathways, mitochondrial biogenesis, and angiogenesis. Notably, tumor progression enhanced the activity of specific transcription factors that regulate the mTORC1 signaling pathway, along with genes involved in translational initiation and ribosome biogenesis. Skeletal muscle-specific, inducible inhibition of mTORC1 activity further exacerbated muscle loss in tumor-bearing mice, highlighting its protective role in maintaining muscle mass. Additionally, we uncovered new intercellular signaling networks within the skeletal muscle microenvironment during pancreatic cancer-induced cachexia. Together, our study revealed previously unrecognized molecular mechanisms that regulates skeletal muscle homeostasis and identified potential therapeutic targets for the treatment of pancreatic cancer–associated cachexia.
Authors
Bowen Xu, Aniket S. Joshi, Meiricris Tomaz da Silva, Silin Liu, Ashok Kumar
Abstract
The lymphatic system maintains fluid homeostasis and orchestrates immune cell trafficking throughout tissues. While extensively studied in cancer and lymphedema, its role in non-lymphoid organs, particularly the kidney, remains an emerging area of investigation. Previous research established molecular connections between NF-κB, VEGFR-3, and PROX-1 in regulating lymphatic growth during inflammation, and studies using global knockout mice revealed that the NF-κB1 subunit (p50) influences lymphatic vessel density. However, the role of RelA—a key component of the canonical NF-κB heterodimer—in regulating lymphatic growth and kidney function following acute kidney injury (AKI) remains unexplored. Using an inducible, predominantly lymphatic-specific RelA knockout mouse model, we demonstrate that RelA expression in VEGFR-3+ cells is essential for VEGFR-3 driven lymphangiogenesis following AKI. Knockout mice exhibited significantly worse kidney function, altered histological features, impaired VEGFR-3-dependent lymphangiogenesis, and dysregulated immune cell trafficking. Compensatory upregulation of PROX-1 and podoplanin occurred despite decreased VEGFR-3 and LYVE-1 total protein expression, suggesting complex regulatory mechanisms. Our findings suggest that RelA is a critical sensor for inflammation and regulator of protective lymphangiogenesis following kidney injury and provide insights into potential therapeutic targets for improved kidney injury outcomes.
Authors
Arin L. Melkonian, Amie M. Traylor, Anna A. Zmijewska, Kyle H. Moore, Gelare Ghajar-Rahimi, Stephanie Esman, Yanlin Jiang, Hani Jang, Babak J. Mehrara, Timmy C. Lee, James F. George, Anupam Agarwal
Abstract
Small cell lung cancer (SCLC) transformation is an incompletely characterized mechanism of resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in EGFR-mutant cancers, limiting development of optimal treatment approaches. Through single-cell RNA sequencing of malignant pleural effusions from patients who underwent SCLC transformation, we identified heterogeneity and diversity, including distinct neuroendocrine (NE) and mesenchymal non-NE cancer cell subsets, which were maintained in patient-derived cell lines. We demonstrate that EZH2 regulates EGFR expression in NE cells where EGFR expression is silenced at baseline. Although neither epigenetic derepression nor exogenous overexpression of mutant EGFR sensitized the cells to EGFR inhibition, non-NE cells exhibited selective sensitivity to MEK inhibitors. Combined MEK inhibitor and chemotherapy effectively inhibited growth of both NE and non-NE cells in vitro and in vivo. Our findings demonstrate that EGFR-mutant SCLC is composed of mixed cell states with distinct therapeutic vulnerabilities and offer a therapeutic strategy to target tumor heterogeneity in highly plastic and treatment-resistant malignancies such as transformed SCLC.
Authors
Atsuko Ogino, Amir Vajdi, Xinmeng Jasmine Mu, Navin R. Mahadevan, Kenneth Ngo, Matthew A. Booker, Paloma Cejas, Jeffrey J. Okoro, Man Xu, Benjamin F. Springer, Benjamin K. Eschle, Cameron M. Messier, Stephen Wang, Sudeepa Syamala, Rubii M. Tamen, Anika E. Adeni, Emily S. Chambers, Israel Canadas, Tran Thai, Camilla L. Christensen, Chunxiao Xu, Patrick H. Lizotte, Geoffrey R. Oxnard, Hideo Watanabe, Henry W. Long, Prafulla C. Gokhale, Cloud P. Paweletz, Lynette M. Sholl, Matthew G. Oser, David A. Barbie, Michael Y. Tolstorukov, Pasi A. Jänne
Abstract
Approximately 30% of patients with endometrial carcinomas (ECs) with exon 3 CTNNB1 (β-catenin) mutations experience disease recurrence, whereas others with the same mutations remain recurrence-free. The molecular factors driving mutant β-catenin’s oncogenic and clinical variability are unknown. Here we show that CD73 restrains the oncogenic activity of exon 3 β-catenin mutants, and CD73 loss is associated with recurrence. Using 7 patient-specific β-catenin mutants, together with genetic deletion or ectopic expression of CD73, we demonstrate that CD73 loss increases β-catenin–TCF/LEF transcriptional activity. In CD73-deficient cells, membrane levels of mutant β-catenin decreased, which corresponded with increased levels of nuclear and chromatin-bound mutant β-catenin. These results suggest that CD73 sequesters mutant β-catenin to the membrane to limit its oncogenic activity. Adenosine A1 receptor deletion phenocopied the effects of CD73 loss, implicating adenosine receptor signaling in this regulation. Ectopic CD73 expression suppressed the invasiveness and stemness capacity of β-catenin–mutant EC cells. TCGA analyses, GeoMx digital spatial profiling, and functional analyses showed that CD73 loss drives distinct Wnt–TCF/LEF–dependent gene expression programs linked to cancer cell stemness. These findings identify CD73 as a key regulator of mutant β-catenin, providing mechanistic insight into the variability of recurrence in CTNNB1-mutant EC.
Authors
Rebecca M. Hirsch, Gaith Droby, Sunthoshini Premsankar, Molly L. Parrish, Katherine C. Kurnit, Lilly F. Chiou, Emily M. Rabjohns, Hannah N. Lee, Russell R. Broaddus, Cyrus Vaziri, Jessica L. Bowser
Abstract
Mitochondrial retrograde signaling plays crucial roles in maintaining metabolic homeostasis via regulating genome modification and oxidative responsive gene expression. In this study, we identified GCN5L1, a protein localized in both mitochondria and cytoplasm, and demonstrated its specific translocation from mitochondria to cytoplasm during lipid overload and high-fat diet feeding. Using transcriptome and proteome analyses, we identified that cytoplasmic GCN5L1 binds to and promotes the acetylation of PPARγ at lysine 289 (K289). This acetylation protected PPARγ from ubiquitination-mediated degradation by proteasome. GCN5L1 translocation enhanced protein stability of PPARγ and subsequently promoted lipid accumulation in both cultured cells and murine models. Our study further reveals that PPARγ-K289 mutation reduces the ubiquitination of PPARγ and exacerbates liver steatosis in mice. These findings unveil a mitochondrial retrograde signaling during lipid overload, which regulates the crucial lipogenic transcriptional factor. This discovery elucidates an unrecognized mitochondrial function and mechanism underlying hepatic lipid synthesis.
Authors
Jiaqi Zhang, Danni Wang, Qiqi Tang, Yaoshu Yue, Xin Lu, Xiuya Hu, Yitong Han, Jiarun Chen, Zihan Wang, Xue Bai, Kai Zhang, Yongsheng Chang, Longhao Sun, Lu Zhu, Lingdi Wang
Abstract
The TRPV4 skeletal dysplasias are characterized by short stature, short limbs with prominent large joints, and progressive scoliosis. They result from dominant missense mutations that activate the TRPV4 calcium permeable ion channel. As a platform to understand the mechanism of disease and to test the hypothesis that channel inhibition could treat these disorders, we developed a knock-in mouse that conditionally expresses the p.R594H Trpv4 mutation. Embryonic, chondrocyte-specific induction of the mutation using Col2a1-Cre resulted in a skeletal dysplasia affecting the long bones, spine, and craniofacial skeletal elements, consistent with the human skeletal dysplasia phenotypes produced by TRPV4 mutations. Cartilage growth plate histological abnormalities included disorganized proliferating chondrocyte columns and reduced hypertrophic chondrocyte development, reflecting abnormal endochondral ossification. In vivo treatment with the TRPV4-specific inhibitor GSK2798745 markedly improved the radiographic skeletal phenotype and rescued the growth plate histological abnormalities. ScRNA-Seq of chondrocyte transcripts from affected mice identified calcium-mediated effects on multiple signaling pathways as potential mechanisms underlying the defects in linear and cartilage appositional growth observed in both mutant mice and patients. These results provide preclinical evidence demonstrating TRPV4 inhibition as a rational, mechanism-based therapeutic strategy to ameliorate disease progression and severity in the TRPV4 skeletal dysplasias.
Authors
Lisette Nevarez, Taylor K. Ismaili, Jennifer Zieba, Jorge Martin, Davis Wachtell, Derick Diaz, Jocelyn A. Ramirez, Valeria Aceves, Joshua Ito, Ryan S. Gray, David Goldstein, Sunil Sahdeo, Deborah Krakow, Daniel H. Cohn
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