FAM120A couples SREBP-dependent transcription and splicing of lipogenesis enzymes downstream of mTORC1

Targeting lipid metabolism via nanomedicine: A prospective strategy for cancer therapy

Lipid metabolism has been increasingly recognized to play an influencing role in tumor initiation, progression, metastasis, and therapeutic drug resistance. Targeting lipid metabolic reprogramming represents a promising therapeutic strategy. Despite their structural complexity and poor targeting efficacy, lipid-metabolizing drugs, either used alone or in combination with chemotherapeutic agents, have been employed in clinical practice. The advent of nanotechnology offers new approaches to enhancing therapeutic effects, includingthe targeted delivery and integration of lipid metabolic reprogramming with chemotherapy, photodynamic therapy (PDT), and immunotherapy. The integrated nanoformulation, nanomedicine, could significantly advance the field of lipid metabolism therapy. In this review, we will briefly introduce the concept of cancer lipid metabolism reprogramming, then elaborate the latest advances in engineered nanomedicine for targeting lipid metabolism during cancer treatment, and finally provide our insights into future perspectives of nanomedicine for interference with lipid metabolism in the tumor microenvironment.

Survival strategies of cancer cells: the role of macropinocytosis in nutrient acquisition, metabolic reprogramming, and therapeutic targeting

Macropinocytosis is a nonselective form of endocytosis that allows cancer cells to largely take up the extracellular fluid and its contents, including nutrients, growth factors, etc. We first elaborate meticulously on the process of macropinocytosis. Only by thoroughly understanding this entire process can we devise targeted strategies against it. We then focus on the central role of the MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) in regulating macropinocytosis, highlighting its significance as a key signaling hub where various pathways converge to control nutrient uptake and metabolic processes. The article covers a comprehensive analysis of the literature on the molecular mechanisms governing macropinocytosis, including the initiation, maturation, and recycling of macropinosomes, with an emphasis on how these processes are hijacked by cancer cells to sustain their growth. Key discussions include the potential therapeutic strategies targeting macropinocytosis, such as enhancing drug delivery via this pathway, inhibiting macropinocytosis to starve cancer cells, blocking the degradation and recycling of macropinosomes, and inducing methuosis - a form of cell death triggered by excessive macropinocytosis. Targeting macropinocytosis represents a novel and innovative approach that could significantly advance the treatment of cancers that rely on this pathway for survival. Through continuous research and innovation, we look forward to developing more effective and safer anti-cancer therapies that will bring new hope to patients.Abbreviation: AMPK: AMP-activated protein kinase; ASOs: antisense oligonucleotides; CAD: carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase; DC: dendritic cell; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; ERBB2: erb-b2 receptor tyrosine kinase 2; ESCRT: endosomal sorting complex required for transport; GAP: GTPase-activating protein; GEF: guanine nucleotide exchange factor; GRB2: growth factor receptor bound protein 2; LPP: lipopolyplex; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin kinase complex 1; MTORC2: mechanistic target of rapamycin kinase complex 2; NSCLC: non-small cell lung cancer; PADC: pancreatic ductal adenocarcinoma; PDPK1: 3-phosphoinositide dependent protein kinase 1; PI3K: phosphoinositide 3-kinase; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns(3,4,5)P3: phosphatidylinositol-(3,4,5)-trisphosphate; PtdIns(4,5)P2: phosphatidylinositol-(4,5)-bisphosphate; PTT: photothermal therapies; RAC1: Rac family small GTPase 1; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase B1; RTKs: receptor tyrosine kinases; SREBF: sterol regulatory element binding transcription factor; TFEB: transcription factor EB; TNBC: triple-negative breast cancer; TSC2: TSC complex subunit 2; ULK1: unc-51 like autophagy activating kinase 1; UPS: ubiquitin-proteasome system.

Splice age: mTORC1-mediated RNA splicing in metabolism and ageing

The target of rapamycin complex mTORC1 has key roles in cell growth and metabolism and its inhibition delays ageing. Recent work by Ogawa et al. in Caenorhabditis elegans argues that modulation of pre-mRNA splicing factors and alternative splicing are key mediators of mTORC1 signalling and can enhance longevity.

mTORC1, the maestro of cell metabolism and growth

The mechanistic target of rapamycin (mTOR) pathway senses and integrates various environmental and intracellular cues to regulate cell growth and proliferation. As a key conductor of the balance between anabolic and catabolic processes, mTOR complex 1 (mTORC1) orchestrates the symphonic regulation of glycolysis, nucleic acid and lipid metabolism, protein translation and degradation, and gene expression. Dysregulation of the mTOR pathway is linked to numerous human diseases, including cancer, neurodegenerative disorders, obesity, diabetes, and aging. This review provides an in-depth understanding of how nutrients and growth signals are coordinated to influence mTOR signaling and the extensive metabolic rewiring under its command. Additionally, we discuss the use of mTORC1 inhibitors in various aging-associated metabolic diseases and the current and future potential for targeting mTOR in clinical settings. By deciphering the complex landscape of mTORC1 signaling, this review aims to inform novel therapeutic strategies and provide a road map for future research endeavors in this dynamic and rapidly evolving field.

Nutrient control of growth and metabolism through mTORC1 regulation of mRNA splicing

Cellular growth and organismal development are remarkably complex processes that require the nutrient-responsive kinase mechanistic target of rapamycin complex 1 (mTORC1). Anticipating that important mTORC1 functions remained to be identified, we employed genetic and bioinformatic screening in C. elegans to uncover mechanisms of mTORC1 action. Here, we show that during larval growth, nutrients induce an extensive reprogramming of gene expression and alternative mRNA splicing by acting through mTORC1. mTORC1 regulates mRNA splicing and the production of protein-coding mRNA isoforms largely independently of its target p70 S6 kinase (S6K) by increasing the activity of the serine/arginine-rich (SR) protein RSP-6 (SRSF3/7) and other splicing factors. mTORC1-mediated mRNA splicing regulation is critical for growth; mediates nutrient control of mechanisms that include energy, nucleotide, amino acid, and other metabolic pathways; and may be conserved in humans. Although mTORC1 inhibition delays aging, mTORC1-induced mRNA splicing promotes longevity, suggesting that when mTORC1 is inhibited, enhancement of this splicing might provide additional anti-aging benefits.

The ataxia-telangiectasia disease protein ATM controls vesicular protein secretion via CHGA and microtubule dynamics via CRMP5

The autosomal recessive disease ataxia-telangiectasia (A-T) presents with cerebellar degeneration, immunodeficiency, radiosensitivity, capillary dilatations, and pulmonary infections. Most symptoms outside the nervous system can be explained by failures of the disease protein ATM as a Ser/Thr-kinase to coordinate DNA damage repair. However, ATM in adult neurons has cytoplasmic localization and vesicle association, where its roles remain unclear. Here, we defined novel ATM protein targets in human neuroblastoma cells, and filtered initial pathogenesis events in ATM-null mouse cerebellum. Profiles of global proteome and phosphoproteomics - both direct ATM/ATR substrates and overall phosphorylation changes - confirmed previous findings for NBN, MRE11, MDC1, CHEK1, EIF4EBP1, AP3B2, PPP2R5C, SYN1 and SLC2A1. Even stronger downregulation of ATM/ATR substrate phosphopeptides after ATM-depletion was documented for CHGA, EXPH5, NBEAL2 and CHMP6 as key factors of protein secretion and endosome dynamics, as well as for CRMP5, DISP2, PHACTR1, PLXNC1, INA and TPX2 as neurite extension factors. Prominent effects on semaphorin-CRMP5-microtubule signals and ATM association with CRMP5 were validated. As a functional consequence, microtubules were stabilized, and neurite retraction ensued. The impact of ATM on secretory granules confirms previous ATM-null cerebellar transcriptome findings. This study provides the first link of A-T neural atrophy to growth cone collapse and aberrant microtubule dynamics.

Metabolic regulation of mRNA splicing

Alternative mRNA splicing enables the diversification of the proteome from a static genome and confers plasticity and adaptiveness on cells. Although this is often explored in development, where hard-wired programs drive the differentiation and specialization, alternative mRNA splicing also offers a way for cells to react to sudden changes in outside stimuli such as small-molecule metabolites. Fluctuations in metabolite levels and availability in particular convey crucial information to which cells react and adapt. We summarize and highlight findings surrounding the metabolic regulation of mRNA splicing. We discuss the principles underlying the biochemistry and biophysical properties of mRNA splicing, and propose how these could intersect with metabolite levels. Further, we present examples in which metabolites directly influence RNA-binding proteins and splicing factors. We also discuss the interplay between alternative mRNA splicing and metabolite-responsive signaling pathways. We hope to inspire future research to obtain a holistic picture of alternative mRNA splicing in response to metabolic cues.

FAM120A deficiency improves resistance to cisplatin in gastric cancer by promoting ferroptosis

The occurrence of chemoresistance is an inescapable obstacle affecting the clinical efficacy of cisplatin in gastric cancer (GC). Exploring the regulatory mechanism of cisplatin resistance will help to provide potential effective targets for improving the prognosis of gastric cancer patients. Here, we find that FAM120A is upregulated in GC tissues and higher in cisplatin-resistant GC tissues, and its high expression is positively correlated with the poor outcome of GC patients. Functional studies indicate that FAM120A confers chemoresistance to GC cells by inhibiting ferroptosis. Mechanically, METTL3-induced m6A modification and YTHDC1-induced stability of FAM120A mRNA enhance FAM120A expression. FAM120A inhibits ferroptosis by binding SLC7A11 mRNA and enhancing its stability. FAM120A deficiency enhances cisplatin sensitivity by promoting ferroptosis in vivo. These results reveal the function of FAM120A in chemotherapy tolerance and targeting FAM120A is an effective strategy to alleviate cisplatin resistance in GC.

Chitosan-Based Sustained Expression of Sterol Regulatory Element-Binding Protein 1a Stimulates Hepatic Glucose Oxidation and Growth in Sparus aurata

The administration of a single dose of chitosan nanoparticles driving the expression of sterol regulatory element-binding protein 1a (SREBP1a) was recently associated with the enhanced conversion of carbohydrates into lipids. To address the effects of the long-lasting expression of SREBP1a on the growth and liver intermediary metabolism of carnivorous fish, chitosan-tripolyphosphate (TPP) nanoparticles complexed with a plasmid expressing the N terminal active domain of hamster SREBP1a (pSG5-SREBP1a) were injected intraperitoneally every 4 weeks (three doses in total) to gilthead sea bream (Sparus aurata) fed high-protein-low-carbohydrate and low-protein-high-carbohydrate diets. Following 70 days of treatment, chitosan-TPP-pSG5-SREBP1a nanoparticles led to the sustained upregulation of SREBP1a in the liver of S. aurata. Independently of the diet, SREBP1a overexpression significantly increased their weight gain, specific growth rate, and protein efficiency ratio but decreased their feed conversion ratio. In agreement with an improved conversion of dietary carbohydrates into lipids, SREBP1a expression increased serum triglycerides and cholesterol as well as hepatic glucose oxidation via glycolysis and the pentose phosphate pathway, while not affecting gluconeogenesis and transamination. Our findings support that the periodical administration of chitosan-TPP-DNA nanoparticles to overexpress SREBP1a in the liver enhanced the growth performance of S. aurata through a mechanism that enabled protein sparing by enhancing dietary carbohydrate metabolisation.