The rockefeller university

The thrombolytic protease tissue plasminogen activator (tPA) is expressed in the CNS, where it regulates diverse functions including neuronal plasticity, neuroinflammation, and blood-brain-barrier integrity. However, its role in different brain regions such as the substantia nigra (SN) is largely unexplored. In this study, we characterize tPA expression, activity, and localization in the SN using a combination of retrograde tracing and beta-galactosidase tPA reporter mice. We further investigate tPA's potential role in SN pathology in an alpha-synuclein mouse model of Parkinson's disease (PD). To characterize the mechanism of tPA action in alpha-synuclein-mediated pathology in the SN and to identify possible therapeutic pathways, we performed RNA-seq analysis of the SN and used multiple transgenic mouse models. These included tPA deficient mice and two newly developed transgenic mice, a knock-in model expressing endogenous levels of proteolytically inactive tPA (tPA Ala-KI) and a second model overexpressing proteolytically inactive tPA (tPA Ala-BAC). Our findings show that striatal GABAergic neurons send tPA+ projections to dopaminergic (DA)-neurons in the SN and that tPA is released from SN-derived synaptosomes upon stimulation. We also found that tPA levels in the SN increased following alpha-synuclein overexpression. Importantly, tPA deficiency protects DA-neurons from degeneration, prevents behavioral deficits, and reduces microglia activation and T-cell infiltration induced by alpha-synuclein overexpression. RNA-seq analysis indicates that tPA in the SN is required for the upregulation of genes involved in the innate and adaptive immune responses induced by alpha-synuclein overexpression. Overexpression of alpha-synuclein in tPA Ala-KI mice, expressing only proteolytically inactive tPA, confirms that tPA-mediated neuroinflammation and neurodegeneration is independent of its proteolytic activity. Moreover, overexpression of proteolytically inactive tPA in tPA Ala-BAC mice leads to increased neuroinflammation and neurodegeneration compared to mice expressing normal levels of tPA, suggesting a tPA dose response. Finally, treatment of mice with glunomab, a neutralizing antibody that selectively blocks tPA binding to the N-methyl-D-aspartate receptor-1 (NMDAR1) without affecting NMDAR1 ion channel function, identifies the tPA interaction with NMDAR1 as necessary for tPA-mediated neuroinflammation and neurodegeneration in response to alpha-synuclein-mediated neurotoxicity. Thus, our data identifies a novel pathway that promotes DA-neuron degeneration and suggests a potential therapeutic intervention for PD targeting the tPA-NMDAR1 interaction.

Enterococcus faecium is a gram-positive bacterium that is resident to the intestines of animals including humans. E. faecium is also an opportunistic pathogen that causes multidrug-resistant (MDR) infections. Bacteriophages (phages) have been proposed as therapeutics for the treatment of MDR infections; however, an obstacle for phage therapy is the emergence of phage resistance. Despite this, the development of phage resistance can impact bacterial fitness. Thus, understanding the molecular basis of fitness costs associated with phage resistance can likely be leveraged as an antimicrobial strategy. We discovered that phage-resistant E. faecium harbor mutations in the cell wall hydrolase gene sagA. SagA cleaves crosslinked peptidoglycan (PG) involved in PG remodeling. We show that mutations in sagA compromised E. faecium PG hydrolysis. One sagA mutant, with a defect in cell envelope integrity, increased cellular permeability, and aberrant distribution of penicillin-binding proteins, was also more sensitive to beta-lactam antibiotics. These changes correspond to a growth defect where cells have abnormal division septa, membrane blebbing, and aberrant cell shape. The dysregulation of the cell envelope caused by the sagA mutation alters the binding of phages to the E. faecium cell surface, where phage infection of E. faecium requires phages to localize to sites of peptidoglycan remodeling. Our findings show that by altering the function of a single PG hydrolase, E. faecium loses intrinsic beta-lactam resistance. This indicates that phage therapy could help revive certain antibiotics when used in combination.IMPORTANCEEnterococcus faecium causes hospital-acquired infections and is frequently resistant to frontline antibiotics, including those that target the cell wall. Bacteriophages represent a promising alternative to combat such infections. However, bacterial adaptation to phage predation often results in resistance. Such resistance is frequently accompanied by fitness trade-offs, most notably altered antibiotic susceptibility. This study provides mechanistic insights into phage resistance-associated antibiotic sensitivity in E. faecium. We show that phage-resistant E. faecium carrying a mutation in the peptidoglycan hydrolase SagA has compromised cell envelope integrity, mislocalized penicillin-binding proteins, and become sensitized to beta-lactam antibiotics. These findings highlight the potential of reviving antibiotics when used in combination with phages in the clinical setting.

BACKGROUND & AIMS: The role of goblet cells in small intestinal inflammation in Crohn's disease (CD) is unknown. Polymorphisms of NOD2 confer risk for CD and associate with small intestinal disease location. We previously showed in mice that Nod2 deficiency leads to overexpansion of Phocaeicola vulgatus in the gut and downstream goblet cell defects, which preceded small intestinal inflammation. In this study, we ask whether goblet cell defects occur in patients with CD with NOD2 polymorphisms and investigate in mice how P vulgatus signals through the intestinal epithelium. METHODS: We performed a retrospective study of patients with CD to assess clinical outcomes and goblet cell histology by NOD2 status. We evaluated the contribution of microbiota and MyD88 signaling in the intestinal epithelium to goblet cell defects in the setting of Nod2 deficiency using genetic mouse models and germ-free mice. RESULTS: In patients with CD who have undergone ileocolic resection, NOD2 risk alleles confer a risk for reoperation (odds ratio, 8.12; P 1/4 .047) and for increased phosphorylated extra-cellular signal-regulated kinase and goblet cell defects in uninflamed ileal tissue. We show that patients with CD with ileal involvement harbor P vulgatus regardless of NOD2 risk allele status. We show that intestinal epithelial MyD88 and TLR4 are required for goblet cell defects in Nod2-/-mice harboring P vulgatus. Finally, we show that P vulgatus requires complex microbiota to exert its effects in Nod2-deficient mice. CONCLUSIONS: Goblet cell defects may be a harbinger of small intestinal inflammation in patients with CD, particularly in the postoperative setting. Our findings in mice show that small intestinal goblet cell loss associated with Nod2 mutation is induced by microbiome dysbiosis and epithelial MyD88, in part due to TLR4 signaling. (Cell Mol Gastroenterol Hepatol 2025; 19:101533; https://doi.org/10.1016/j.jcmgh.2025.101533)

Approximately 3.4 million patients worldwide are diagnosed each year with cancers that have pathogenic mutations in one of three RAS proto-oncogenes (KRAS, NRAS and HRAS)1,2. These mutations impair the GTPase activity of RAS, leading to activation of downstream signalling and proliferation3, 4, 5-6. Long-standing efforts to restore the hydrolase activity of RAS mutants have been unsuccessful, extinguishing any consideration towards a viable therapeutic strategy7. Here we show that tri-complex inhibitors-that is, molecular glues with the ability to recruit cyclophilin A (CYPA) to the active state of RAS-have a dual mechanism of action: not only do they prevent activated RAS from binding to its effectors, but they also stimulate GTP hydrolysis. Drug-bound CYPA complexes modulate residues in the switch II motif of RAS to coordinate the nucleophilic attack on the gamma-phosphate of GTP in a mutation-specific manner. RAS mutants that were most sensitive to stimulation of GTPase activity were more susceptible to treatment than mutants in which the hydrolysis could not be enhanced, suggesting that pharmacological stimulation of hydrolysis potentiates the therapeutic effects of tri-complex inhibitors for specific RAS mutants. This study lays the foundation for developing a class of therapeutics that inhibit cancer growth by stimulating mutant GTPase activity.

Following transcript release during intrinsic termination, Escherichia coli RNA polymerase (RNAP) often remains associated with DNA in a post-termination complex (PTC). RNAPs in PTCs are removed from the DNA by the SWI2/SNF2 adenosine triphosphatase (ATPase) RapA. Here we determined PTC structures on negatively supercoiled DNA and with RapA engaged to dislodge the PTC. We found that core RNAP in the PTC can unwind DNA and initiate RNA synthesis but is prone to producing R-loops. Nucleotide binding to RapA triggers a conformational change that opens the RNAP clamp, allowing DNA in the RNAP cleft to reanneal and dissociate. We show that RapA helps to control cytotoxic R-loop formation in vivo, likely by disrupting PTCs. We suggest that analogous ATPases acting on PTCs to suppress transcriptional noise and R-loop formation may be widespread. These results hold importance for the bacterial transcription cycle and highlight a role for RapA in maintaining genome stability.

Aging is the primary risk factor for many diseases, including neurodegenerative disorders, cardiovascular diseases, and cancer. The rapid advancement of single-cell sequencing technologies has opened promising avenues for investigating aging-associated cellular changes that contribute to disrupted system homeostasis and increased vulnerability to age-related diseases. Despite the abundance of data generated over the past decade, a systematic understanding of how aging affects cell type-specific populations across the entire mammalian organism remains lacking-a critical gap for elucidating the cellular foundations of aging-related system dysfunction. In this review, we address this knowledge gap by summarizing recent single-cell studies examining the impact of aging on cell type-specific population changes across mammalian organs. We also review the impact of gender and antiaging interventions on cell population dynamics in aged mammals. This work provides a comprehensive catalog of cellular states susceptible to aging, highlighting potential therapeutic targets for aging and age-related diseases.

Suicide is a major public health concern, and the number of deaths by suicide has been increasing in recent years in the US. There are various biological risk factors for suicide, but causal molecular mechanisms remain unknown, suggesting that investigation of novel mechanisms and integrative approaches are necessary. Transfer (t)RNAs and their modifications, including cytosine methylation (m5C), have received little attention regarding their role in normal or diseased brain function, though they are dynamic mediators of protein synthesis. tRNA regulation is highly interconnected with proteomic and metabolomic outcomes, suggesting that investigating these multiple levels of molecular regulation together may elucidate more information on neural function and suicide risk. In the current study, we used an integrative 'omics' approach to probe tRNA dysregulation, including tRNA expression and tRNA m5C, proteomics, and amino acid metabolomics in prefrontal cortex from 98 subjects who died by suicide during an episode of major depressive disorder (MDD) and neurotypical controls. While no changes were detected in amino acid content, results showed increased tRNAGlyGCC expression in the suicide brain that is not driven by changes in m5C. Proteomics revealed increased expression of proteins with high glycine codon GGC content, demonstrating a strong association between isoacceptor-specific tRNA expression and proteomic outcomes in the suicide brain, which is in line with previous work linking tRNAGly with alterations in glycine-rich proteins in a translational rodent model of depression. Further, we confirmed using a rodent model that tRNAGlyGCC overexpression was sufficient to increase the expression of proteins with high glycine codon GGC content that were upregulated in the suicide brain. By characterizing the effects of MDD-suicide in human PFC tissue, we now begin to elucidate a novel molecular signature with downstream consequences for psychiatric outcomes.