Otoshi et al. report a genetic background-dependent hyperactive TGF-β/PDGFRA/TNC program unleashed by a brief in utero exposure to a vitamin A/retinoic acid–deficient environment, resulting in structural remodeling of the airway smooth muscle and hyperresponsiveness in adult mice. The cover image shows the aberrant ectopic expansion of PDGFRA (red) where airway smooth muscle emerges in the embryonic lung near distal epithelial buds (SOX9, green) and airway epithelial progenitors (SOX2, cyan).
Wnt signaling drives tumorigenesis in multiple cancers, in part through complex interactions with other oncogenic pathways including the MAPK cascade. In Wnt-addicted cancers, pharmacologic and genetic inhibition of Wnt signaling activates multiple receptor tyrosine kinases (RTKs), increases ERK phosphorylation and induces MAPK target gene expression, but the specific RTKs responsible for this MAPK hyperactivation are not known. Here we performed phosphotyrosine-targeted mass spectrometry, which revealed robust phosphorylation of EPHA2 and EGFR upon Wnt inhibition. Unexpectedly, we find that in xenografts, EPHA2 suppresses EGFR and ERK activation. Most notably, the increased ERK phosphorylation observed in EPHA2 KO tumors is transcriptionally inert, as there is no concomitant increase in MAPK target gene expression until concomitant Wnt inhibition. This suggests a Wnt-activated transcriptional repressor such as GATA3 that gates MAPK signaling in Wnt-high cancers. While Wnt-high KRAS-mutant cancers are resistant to erlotinib alone, adding Wnt inhibitor mitigates this resistance. Additionally, loss of EPHA2 enhances their sensitivity to both erlotinib and Wnt inhibitors. These studies therefore identify therapeutic vulnerabilities in Wnt-high tumors, even within traditionally EGFR inhibitor-resistant, RAS-mutant contexts.
Shawn R. Wadia, Changyuan Hu, Siddhi Patnaik, Shreya Sridharan, Roger J. Daly, David M. Virshup, Babita Madan
Autophagy is a critical host defense mechanism that restricts intracellular pathogens such as Mycobacterium tuberculosis (Mtb). A key step in this process is the ubiquitination of Mtb or Mtb-associated structures. The E3 ligase SMURF1 catalyzes K48-linked ubiquitination, promoting bacterial clearance. However, the function of its homolog, SMURF2, in host defense remains undefined. Here, we demonstrate that Smurf2 deletion in murine macrophages increases SMURF1 levels, enhances LC3B lipidation, augments K48 ubiquitination of Mtb-associated structures, and reduces intracellular Mtb replication. These effects are reversed by Smurf1 deletion, supporting a role for SMURF1 in SMURF2-dependent control of Mtb. Mice with myeloid-specific Smurf2 deletion exhibit modestly prolonged survival following aerosol Mtb infection. In human macrophages, SMURF2 knockdown or its pharmacological inhibition with the HECT E3-ligase inhibitor Heclin reduces Mtb replication. Together, our findings identify SMURF2 as a negative regulator of macrophage control of Mtb and support further investigation of SMURF2 as a potential target for host-directed therapy in tuberculosis.
Priscila C. Campos, Kathryn C. Rahlwes, Victoria A. Ektnitphong, Beatriz R.S. Dias, Kubra F. Naqvi, Samuel Alvarez-Arguedas, Michael U. Shiloh
Fractures heal by rapid formation of mineralized callus, a process requiring periosteal cell proliferation and differentiation. Our objective was to dissect the contribution of proliferating osteoblast lineage cells to fracture callus formation. First, mice expressing thymidine kinase (TK) in 3.6Col1a1-lineage cells were treated with ganciclovir (GCV) to ablate proliferating osteolineage cells for 5 or 10 days. Immunostaining demonstrated that this approach specifically depleted TK+ proliferating cells in the bony regions of the callus, while sparing other proliferating cells. Single-cell RNA-seq of callus cells revealed that GCV-treated Col1-TK mice had fewer osteoblasts and chondrocytes than controls, with more myofibroblasts and immune cells, consistent with fibrous nonunion. In controls, 15-30% of callus cells expressing the early osteoblast markers osterix (Sp7) and the late marker osteocalcin (Bglap) were in the cell cycle. Next, we targeted proliferating osteolineage cells at different stages of differentiation by crossing Osx-CreERT2, Ocn-Cre and Dmp1-CreERT2 mice with ROSA-TK mice. Following fracture, each Cre;ROSA-TK mouse line exhibited decreased callus bone volume and a shift from callus bone to fibrous tissue. Therefore, during fracture repair, proliferation of callus cells at early and mature stages of osteoblast differentiation is critical to the formation of a mineralized callus that is essential for healing.
Nicole R. Gould, Andre F. Coello, Jennifer A. McKenzie, Mariam Obaji, Tiandao Li, Katherine R. Hixon, Leyi Chen, Kristen Barwick, Tiffany Lee, Bo A. Zhang, David Ornitz, Matthew J. Silva
Mutations in mitochondrial DNA (mtDNA) cause various mitochondrial diseases that are currently incurable. Allotopic expression of nuclear-recoded mitochondrial genes represents a promising therapeutic strategy, given its demonstrated capacity to restore mitochondrial function in human cell models harboring mtDNA mutations. However, the in vivo evaluation of allotopic gene therapy has been hindered by optimization challenges and the lack of appropriate animal models. Here, we overcome these limitations by utilizing an optimized AAV2-ND6 construct with codon optimization and mitochondrial targeting sequence in a mouse model bearing the homoplasmic ND6P25L mutation, which recapitulates Leber hereditary optic neuropathy (LHON). High-dose administration of the AAV2-ND6 construct resulted in robust, sustained expression within the retina and optic nerve without apparent systemic toxicity. Strikingly, We compared the therapeutic efficacy in mutant mice at different ages and pre-symptomatic intervention with AAV2-ND6 effectively attenuated disease progression, mitigated retinal cellular deficiencies and optic nerve damage, and restored visual function in ND6P25L mice. Mechanistically, allotopic ND6 expression markedly rescued the mitochondrial dysfunction, corrected dysregulated retinol metabolism and phototransduction pathways, and suppressed apoptotic processes in the mutant retina. Our study validates the safety and therapeutic potential of allotopic expression in vivo and provide critical mechanistic insights into its role in treating LHON and other mitochondrial diseases.
Cheng Ai, Huiying Li, Jing Wu, Tianwei Zhou, Jing Wang, Shao-Hui Pan, Jun Yu, Douglas C. Wallace, Min-Xin Guan
Inflammatory cytokines reprogram keratinocyte metabolism, but the metabolic pathways that couple immune signals to pathological epidermal growth remain incompletely defined. Here, we identify GLS1-mediated glutaminolysis as a metabolic program preferentially induced in keratinocytes under type 3 inflammatory conditions. Integrated transcriptomic, metabolomic, genetic, and functional analyses showed that IL-17A induced GLS1 expression and glutaminolysis in keratinocytes. Keratinocyte-specific Gls1 deletion reduced the intracellular availability of arginine, proline, and methionine, impaired amino acid-dependent mTORC1 activation, disrupted redox homeostasis, and limited keratinocyte proliferation. Amino acid or antioxidant supplementation partially rescued these defects, whereas rapamycin blocked the amino acid-mediated proliferative rescue. Gls1 deletion did not impair steady-state skin development or homeostasis and did not alter MC903-induced type 2 dermatitis, but it delayed wound re-epithelialization and attenuated IMQ-induced psoriasiform inflammation. Loss of keratinocyte GLS1 also reduced epidermal chemokine expression and the accumulation of neutrophils and IL-17A-producing γδ T cells, revealing a role for glutaminolysis in amplifying epithelial-immune crosstalk. These findings define GLS1-mediated glutaminolysis as a context-specific metabolic checkpoint linking type 3 inflammation to keratinocyte proliferation and cutaneous immune amplification, and support locally or temporally controlled GLS1 inhibition as a potential therapeutic strategy for psoriasis.
Yongfei Hu, Hai Yu, Kaiyu Liang, Liyan Yuan, Wenjun Zhang, Zhe Zhuang, Suyun Ji, Xichun Xia