Epigenetic editing of PCSK9 for a durable reduction in cholesterol
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Prime editing: therapeutic advances and mechanistic insights
We are often confronted with a simple question, “which gene editing technique is the best?”; the simple answer is “there isn’t one”. In 2021, a year after prime editing first made its mark, we evaluated the landscape of this potentially transformative advance in genome engineering towards getting treatments to the clinic [1]. Nearly 20% of the papers we cited were still in pre-print at the time which serves to indicate how early-stage the knowledge base was at that time. Now, three years later, we take a look at the landscape and ask what has been learnt to ensure this tech is broadly accessible, highlighting some key advances, especially those that push this towards the clinic. A big part of the appeal of prime editing is its ability to precisely edit DNA without double stranded breaks, and to install any of the 12 possible single-nucleotide conversion events as well as small insertions and/or deletions, or essentially any combination thereof. Over the last few decades, other transformative and Nobel prize-winning technologies that rely on Watson-Crick base-pairing such as PCR, site-directed mutagenesis, RNA interference, and one might say, “classic” CRISPR, were swiftly adopted across labs around the world because of the speed with which mechanistic rules governing their efficiency were determined. Whilst this perspective focuses on the context of gene therapy applications of prime editing, we also further look at the recent studies which have increased our understanding of the mechanism of PEs and simultaneously improved the efficiency and diversity of the PE toolbox.
A torpor-like state in mice slows blood epigenetic aging and prolongs healthspan
Torpor and hibernation are extreme physiological adaptations of homeotherms associated with pro-longevity effects. Yet the underlying mechanisms of how torpor affects aging, and whether hypothermic and hypometabolic states can be induced to slow aging and increase healthspan, remain unknown. Here we demonstrate that the activity of a spatially defined neuronal population in the preoptic area, which has previously been identified as a torpor-regulating brain region, is sufficient to induce a torpor-like state (TLS) in mice. Prolonged induction of TLS slows epigenetic aging across multiple tissues and improves healthspan. We isolate the effects of decreased metabolic rate, long-term caloric restriction, and decreased core body temperature (Tb) on blood epigenetic aging and find that the decelerating effect of TLSs on aging is mediated by decreased Tb. Taken together, our findings provide novel mechanistic insight into the decelerating effects of torpor and hibernation on aging and support the growing body of evidence that Tb is an important mediator of the aging processes.
Modulation of the human GlyT1 by clinical drugs and cholesterol
Glycine transporter 1 (GlyT1) is a key player in shaping extracellular glutamatergic signaling processes and holds promise for treating cognitive impairments associated with schizophrenia by inhibiting its activity and thus enhancing the function of NMDA receptors. Despite its significant role in physiological and pharmacology, its modulation mechanism by clinical drugs and internal lipids remains elusive. Here, we determine cryo-EM structures of GlyT1 in its apo state and in complex with clinical trial drugs iclepertin and sarcosine. The GlyT1 in its apo state is determined in three distinct conformations, exhibiting a conformational equilibrium of the transport cycle. The complex structures with inhibitor iclepertin and sarcosine elucidate their unique binding poses with GlyT1. Three binding sites of cholesterol are determined in GlyT1, two of which are conformation-dependent. Transport kinetics studies reveal that a delicate binding equilibrium for cholesterol is crucial for the conformational transition of GlyT1. This study significantly enhances our understanding of the physiological and pharmacological aspects of GlyT1.
Cholesterol homeostasis and lipid raft dynamics at the basis of tumor-induced immune dysfunction in chronic lymphocytic leukemia
Autologous T-cell therapies show limited efficacy in chronic lymphocytic leukemia (CLL), where acquired immune dysfunction prevails. In CLL, disturbed mitochondrial metabolism has been linked to defective T-cell activation and proliferation. Recent research suggests that lipid metabolism regulates mitochondrial function and differentiation in T cells, yet its role in CLL remains unexplored. This comprehensive study compares T-cell lipid metabolism in CLL patients and healthy donors, revealing critical dependence on exogenous cholesterol for human T-cell expansion following TCR-mediated activation. Using multi-omics and functional assays, we found that T cells present in viably frozen samples of patients with CLL (CLL T cells) showed impaired adaptation to cholesterol deprivation and inadequate upregulation of key lipid metabolism transcription factors. CLL T cells exhibited altered lipid storage, with increased triacylglycerols and decreased cholesterol, and inefficient fatty acid oxidation (FAO). Functional consequences of reduced FAO in T cells were studied using samples from patients with inherent FAO disorders. Reduced FAO was associated with lower T-cell activation but did not affect proliferation. This implicates low cholesterol levels as a primary factor limiting T-cell proliferation in CLL. CLL T cells displayed fewer and less clustered lipid rafts, potentially explaining the impaired immune synapse formation observed in these patients. Our findings highlight significant disruptions in lipid metabolism as drivers of functional deficiencies in CLL T cells, underscoring the pivotal role of cholesterol in T-cell proliferation. This study suggests that modulating cholesterol metabolism could enhance T-cell function in CLL, presenting novel immunotherapeutic approaches to improve outcome in this challenging disease.
Proteogenomic characterization reveals tumorigenesis and progression of lung cancer manifested as subsolid nodules
Lung adenocarcinoma (LUAD) radiologically displayed as subsolid nodules (SSNs) is prevalent. Nevertheless, the precise clinical management of SSNs necessitates a profound understanding of their tumorigenesis and progression. Here, we analyze 66 LUAD displayed as SSNs covering 3 histological stages including adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IAC) by incorporating genomics, proteomics, phosphoproteomics and glycoproteomics. Intriguingly, cholesterol metabolism is aberrantly regulated in the preneoplastic AIS stage. Importantly, target ablation of proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the initiation of LUAD. Furthermore, sustained endoplasmic reticulum stress is demonstrated to be a hallmark and a reliable biomarker of AIS progression to IAC. Consistently, target promotion of ER stress profoundly retards LUAD progression. Our study provides comprehensive proteogenomic landscape of SSNs, sheds lights on the tumorigenesis and progression of SSNs and suggests preventive and therapeutic strategies for LUAD.
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