bims-raghud Biomed News
on RagGTPases in human diseases
Issue of 2024‒10‒13
twelve papers selected by
Irene Sambri, TIGEM
  1. Hyperactive mTORC1/4EBP1 signaling dysregulates proteostasis and accelerates cardiac aging.
  2. Transcription factor EB (TFEB) promotes autophagy in early brain injury after subarachnoid hemorrhage in rats.
  3. Spatial and functional separation of mTORC1 signalling in response to different amino acid sources.
  4. Role of TFEB lactylation.
  5. The dual role of lipids in chronic kidney disease: Pathogenic culprits and therapeutic allies.
  6. Ferroptosis: A New Strategy for the Treatment of Fibrotic Diseases.
  7. AKT-mediated phosphorylation of TSC2 controls stimulus- and tissue-specific mTORC1 signaling and organ growth.
  8. Coordinating BNIP3/NIX-mediated mitophagy in space and time.
  9. CRISPR activation of Tfeb , a master regulator of autophagy and lysosomal biogenesis, in osteoblast lineage cells increases bone mass and strength.
  10. O-GlcNAcylation modulates mTORC1 and autophagy in β-cells, driving diabetes progression.
  11. Maturation of pluripotent stem cell-derived cardiomyocytes: limitations and challenges from metabolic aspects.
  12. Atrial natriuretic peptide (ANP) modulates stress-induced autophagy in endothelial cells.
  1. Geroscience. 2024 Oct 09.
    Hyperactive mTORC1/4EBP1 signaling dysregulates proteostasis and accelerates cardiac aging.
    Weronika Zarzycka, Kamil A Kobak, Catherine J King, Frederick F Peelor, Benjamin F Miller, Ying Ann Chiao.
      The mechanistic target of rapamycin complex 1 (mTORC1) has a major impact on aging by regulation of proteostasis. It is well established that mTORC1 signaling is hyperactivated with aging and age-related diseases. Previous studies have shown that partial inhibition of mTOR signaling by rapamycin reverses age-related deteriorations in cardiac function and structure in old mice. However, the downstream signaling pathways involved in this protection against cardiac aging have not been established. mTORC1 phosphorylates 4E-binding protein 1 (4EBP1) to promote the initiation of cap-dependent translation. The objective of this project is to examine the role of the mTORC1/4EBP1 axis in age-related cardiac dysfunction. We used a whole-body 4EBP1 KO mouse model, which mimics a hyperactive mTORC1/4EBP1/eIF4E axis, to investigate the effects of hyperactive mTORC1/4EBP1 axis in cardiac aging. Echocardiographic measurements of middle-aged 4EBP1 KO mice show impaired diastolic function and myocardial performance compared to age-matched WT mice and these parameters are at similar levels as old WT mice, suggesting that 4EBP1 KO mice experience accelerated cardiac aging. Old 4EBP1 KO mice show further decline in systolic and diastolic function compared to middle-aged counterparts and have worse systolic and diastolic function than age-matched WT mice. Gene expression levels of heart failure markers are not different between 4EBP1 KO and WT hearts. However, ribosomal biogenesis and protein ubiquitination are significantly increased in 4EBP1 KO hearts when compared to WT controls, suggesting dysregulated proteostasis in 4EBP1 KO hearts. Together, these results show that a hyperactive mTORC1/4EBP1 axis accelerates cardiac aging, potentially by dysregulating proteostasis.
    Keywords:  4EBP1; Cardiac aging; Proteostasis; mTOR
    DOI:  https://doi.org/10.1007/s11357-024-01368-w
  2. Neurosurg Rev. 2024 Oct 08. 47(1): 741
    Transcription factor EB (TFEB) promotes autophagy in early brain injury after subarachnoid hemorrhage in rats.
    Wenqi Lu, Haichao Chu, Chunchen Yang, Xiaoxu Li.
      Subarachnoid hemorrhage (SAH) has high mortality. Early brain injury (EBI) is responsible for unfavorable outcomes for patients with SAH. The protective involvement of autophagy in hemorrhagic stroke has been proposed. The transcription factor EB (TFEB) can increase autophagic flux by promoting autophagosome formation and autophagosome-lysosome fusion, and dysregulation of TFEB activity might induce the development of several diseases. However, the biological functions of TFEB in EBI after SAH remain unknown. We established an animal model of SAH by the modified endovascular perforation method. Expression of TFEB and autophagy required genes was measured by western blotting and immunofluorescence staining. SAH grading, brain water content and neurobehavioral functions were evaluated at 24 h post-SAH. Neuronal apoptosis in cerebral cortex was assessed by TUNEL staining and Fluoro Jade B staining. TFEB was downregulated in SAH rats, and its overexpression reduced brain edema and ameliorated neurological deficits of SAH rats. Additionally, the neuronal apoptosis induced by SAH was inhibited by TFEB overexpression. Moreover, TFEB overexpression promoted autophagy after SAH. TFEB overexpression promotes autophagy to inhibit neuronal apoptosis, brain edema and neurological deficits post-SAH.
    Keywords:  Apoptosis; Autophagy; Neurologic deficits; Subarachnoid hemorrhage; TFEB
    DOI:  https://doi.org/10.1007/s10143-024-02879-y
  3. Nat Cell Biol. 2024 Oct 09.
    Spatial and functional separation of mTORC1 signalling in response to different amino acid sources.
    Stephanie A Fernandes, Danai-Dimitra Angelidaki, Julian Nüchel, Jiyoung Pan, Peter Gollwitzer, Yoav Elkis, Filippo Artoni, Sabine Wilhelm, Marija Kovacevic-Sarmiento, Constantinos Demetriades.
      Amino acid (AA) availability is a robust determinant of cell growth through controlling mechanistic/mammalian target of rapamycin complex 1 (mTORC1) activity. According to the predominant model in the field, AA sufficiency drives the recruitment and activation of mTORC1 on the lysosomal surface by the heterodimeric Rag GTPases, from where it coordinates the majority of cellular processes. Importantly, however, the teleonomy of the proposed lysosomal regulation of mTORC1 and where mTORC1 acts on its effector proteins remain enigmatic. Here, by using multiple pharmacological and genetic means to perturb the lysosomal AA-sensing and protein recycling machineries, we describe the spatial separation of mTORC1 regulation and downstream functions in mammalian cells, with lysosomal and non-lysosomal mTORC1 phosphorylating distinct substrates in response to different AA sources. Moreover, we reveal that a fraction of mTOR localizes at lysosomes owing to basal lysosomal proteolysis that locally supplies new AAs, even in cells grown in the presence of extracellular nutrients, whereas cytoplasmic mTORC1 is regulated by exogenous AAs. Overall, our study substantially expands our knowledge about the topology of mTORC1 regulation by AAs and hints at the existence of distinct, Rag- and lysosome-independent mechanisms that control its activity at other subcellular locations. Given the importance of mTORC1 signalling and AA sensing for human ageing and disease, our findings will probably pave the way towards the identification of function-specific mTORC1 regulators and thus highlight more effective targets for drug discovery against conditions with dysregulated mTORC1 activity in the future.
    DOI:  https://doi.org/10.1038/s41556-024-01523-7
  4. Nat Cell Biol. 2024 Oct;26(10): 1629
    Role of TFEB lactylation.
    Petra Gross.
      
    DOI:  https://doi.org/10.1038/s41556-024-01533-5
  5. Atherosclerosis. 2024 Sep 25. pii: S0021-9150(24)01187-0. [Epub ahead of print] 118615
    The dual role of lipids in chronic kidney disease: Pathogenic culprits and therapeutic allies.
    Elena Giardini, Dean Moore, Denise Sadlier, Catherine Godson, Eoin Brennan.
      Chronic kidney disease (CKD) is a significant health burden, with rising incidence and prevalence, attributed in part to increasing obesity and diabetes rates. Lipid accumulation in the kidney parenchyma and chronic, low-grade inflammation are believed to significantly contribute to the development and progression of CKD. The effect of dysregulated kidney lipid metabolism in CKD progression, including altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury through the activation of oxidative stress and inflammatory signalling cascades. In contrast, classes of endogenous specialized pro-resolving lipid mediators (SPMs) have been described that act to limit the inflammatory response and promote the resolution of inflammation. This review highlights our current understanding of how lipids can cause damage within the kidney, and classes of protective lipid metabolites that offer therapeutic benefits.
    Keywords:  Glomerulosclerosis; Lipids; Lipoxsin; Maresins; Pro-resolving mediators; Protectins; Resolvins; Tubulointerstitial fibrosis; chronic kidney disease; inflammation
    DOI:  https://doi.org/10.1016/j.atherosclerosis.2024.118615
  6. Adv Biol (Weinh). 2024 Oct 08. e2400383
    Ferroptosis: A New Strategy for the Treatment of Fibrotic Diseases.
    Zhuo Pei, Jing Fan, Maolin Tang, Yuhong Li.
      Ferroptosis is a new type of cell death characterized by iron dependence and the excessive accumulation of lipid reactive oxygen species (lipid ROS) that has gradually become better characterized. There is sufficient evidence indicating that ferroptosis is associated with a variety of human life activities and diseases, such as tumor suppression, ischemic organ injury, and degenerative disorders. Notably, ferroptosis is also involved in the initiation and development of fibrosis in various organs, including liver fibrosis, pulmonary fibrosis, renal fibrosis, and cardiac fibrosis, which is usually irreversible and refractory. Although a large number of patients with fibrosis urgently need to be treated, the current treatment options are still limited and unsatisfactory. Organ fibrosis involves a series of complex and orderly processes, such as parenchymal cell damage, recruitment of inflammatory cells and activation of fibroblasts, which ultimately leads to the accumulation of extracellular matrix (ECM) and the formation of fibrosis. An increasing number of studies have confirmed the close association between these pathological processes and ferroptosis. This review summarizes the role and function of ferroptosis in fibrosis and proposes several potential therapeutic strategies and pathways based on ferroptosis.
    Keywords:  Iron; ferroptosis; fibrosis; treatment
    DOI:  https://doi.org/10.1002/adbi.202400383
  7. bioRxiv. 2024 Sep 23. pii: 2024.09.23.614519. [Epub ahead of print]
    AKT-mediated phosphorylation of TSC2 controls stimulus- and tissue-specific mTORC1 signaling and organ growth.
    Yann Cormerais, Samuel C Lapp, Krystle C Kalafut, Madi Y Cissé, Jong Shin, Benjamin Stefadu, Jean Personnaz, Sandra Schrotter, Angelica D'Amore, Emma R Martin, Catherine L Salussolia, Mustafa Sahin, Suchithra Menon, Vanessa Byles, Brendan D Manning.
      Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) integrates diverse intracellular and extracellular growth signals to regulate cell and tissue growth. How the molecular mechanisms regulating mTORC1 signaling established through biochemical and cell biological studies function under physiological states in specific mammalian tissues are unknown. Here, we characterize a genetic mouse model lacking the 5 phosphorylation sites on the tuberous sclerosis complex 2 (TSC2) protein through which the growth factor-stimulated protein kinase AKT can active mTORC1 signaling in cell culture models. These phospho-mutant mice (TSC2-5A) are developmentally normal but exhibit reduced body weight and the weight of specific organs, such as brain and skeletal muscle, associated with cell intrinsic decreases in growth factor-stimulated mTORC1 signaling. The TSC2-5A mouse model demonstrates that TSC2 phosphorylation is a primary mechanism of mTORC1 activation in some, but not all, tissues and provides a genetic tool to facilitate studies on the physiological regulation of mTORC1.
    DOI:  https://doi.org/10.1101/2024.09.23.614519
  8. Biochem Soc Trans. 2024 Oct 08. pii: BST20221364. [Epub ahead of print]
    Coordinating BNIP3/NIX-mediated mitophagy in space and time.
    Natalie M Niemi, Jonathan R Friedman.
      Mitochondria maintain organellar homeostasis through multiple quality control pathways, including the clearance of defective or unwanted mitochondria by selective autophagy. This removal of mitochondria, mitophagy, is controlled in large part by the outer mitochondrial membrane mitophagy receptors BNIP3 and NIX. While it has long been appreciated that BNIP3 and NIX mediate mitophagy by controlling the recruitment of autophagic machinery to the mitochondrial surface, the requirement for the carefully controlled spatiotemporal regulation of receptor-mediated mitophagy has only recently come to light. Several new factors that regulate the BNIP3/NIX-mediated mitophagy pathway have emerged, and various loss-of-function cell and animal models have revealed the dire consequences of their dysregulation. In this mini-review, we discuss new insights into the mechanisms and roles of the regulation of BNIP3 and NIX and highlight questions that have emerged from the identification of these new regulators.
    Keywords:  autophagy; mitochondria; mitophagy
    DOI:  https://doi.org/10.1042/BST20221364
  9. bioRxiv. 2024 Sep 26. pii: 2024.09.26.615175. [Epub ahead of print]
    CRISPR activation of Tfeb , a master regulator of autophagy and lysosomal biogenesis, in osteoblast lineage cells increases bone mass and strength.
    Alicen James, James Hendrixson, Ilham Kadhim, Adriana Marques-Carvalho, Jacob Laster, Julie Crawford, Jeff Thostenson, Amy Sato, Maria Almeida, Melda Onal.
      Autophagy is a recycling pathway in which damaged or dysfunctional proteins, protein aggregates, and organelles are delivered to lysosomes for degradation. Insufficiency of autophagy is thought to contribute to several age-related diseases including osteoporosis. Consistent with this, elimination of autophagy from the osteoblast lineage reduces bone formation and causes low bone mass. However, whether increasing autophagy would benefit bone health is unknown. Here, we increased expression of the endogenous Transcription Factor EB gene ( Tfeb ) in osteoblast lineage cells in vivo via CRISPR activation. Tfeb overexpression stimulated autophagy and lysosomal biogenesis in osteoblasts. Tfeb overexpressing male mice displayed a robust increase in femoral and vertebral cortical thickness at 4.5 months of age. Histomorphometric analysis revealed that the increase in femoral cortical thickness was due to increased bone formation at the periosteal surface. Tfeb overexpression also increased femoral trabecular bone volume. Consistent with these results, bone strength was increased in Tfeb overexpressing mice. Female Tfeb overexpressing mice also displayed a progressive increase in bone mass over time and at 12 months of age had high cortical thickness and trabecular bone volume. This increase in vertebral trabecular bone volume was due to elevated bone formation. Osteoblastic cultures showed that Tfeb overexpression increased proliferation and osteoblast formation. Overall, these results demonstrate that stimulation of autophagy in osteoblast lineage cells promotes bone formation and strength and may represent an effective approach to combat osteoporosis.
    DOI:  https://doi.org/10.1101/2024.09.26.615175
  10. JCI Insight. 2024 Oct 10. pii: e183033. [Epub ahead of print]
    O-GlcNAcylation modulates mTORC1 and autophagy in β-cells, driving diabetes progression.
    Seokwon Jo, Nicholas Esch, Anh Nguyen, Alicia Wong, Ramkumar Mohan, Clara Kim, Manuel Blandino-Rosano, Ernesto Bernal-Mizrachi, Emilyn U Alejandro.
      Type 2 diabetes (T2D) arises when pancreatic β-cells fail to produce sufficient insulin to control blood glucose appropriately. Aberrant nutrient sensing by O-GlcNAcylation and mTORC1 is linked to T2D and the failure of insulin-producing β-cells. However, the nature of their crosstalk in β-cells remains unexplored. Recently, O-GlcNAcylation, a post-translation modification controlled by enzymes OGT/OGA, emerged as a pivotal regulator for β-cell health; deficiency in either enzyme causes β-cell failure. The present study investigates the previously unidentified connection between nutrient sensor OGT and mTORC1 crosstalk to regulate β-cell mass and function in vivo. We show reduced OGT and mTORC1 activity in islets of preclinical β-cell dysfunction model and obese human islets. Using loss or gain of function of OGT, we identified that O-GlcNAcylation positively regulates mTORC1 signaling in β-cells. O-GlcNAcylation negatively modulates autophagy, as the removal of OGT increases autophagy, while the deletion of OGA decreases it. Increasing mTORC1 signaling, via deletion of TSC2, alleviates the diabetic phenotypes by increasing β-cell mass but not β-cell function in OGT deficient mice. Downstream phospho-protein signaling analysis reveal diverging impact on MKK4 and calmodulin signaling between islets with OGT, TSC2, or combined deletion. These data provide new evidence of OGT's significance as an upstream regulator of mTORC1 and autophagy, crucial for the regulation of β-cell function and glucose homeostasis.
    Keywords:  Autophagy; Beta cells; Diabetes; Endocrinology; Metabolism
    DOI:  https://doi.org/10.1172/jci.insight.183033
  11. Stem Cell Res Ther. 2024 Oct 08. 15(1): 354
    Maturation of pluripotent stem cell-derived cardiomyocytes: limitations and challenges from metabolic aspects.
    Xi Jiang, Xin Lian, Kun Wei, Jie Zhang, Kaihua Yu, Haoming Li, Haichun Ma, Yin Cai, Lei Pang.
      Acute coronary syndromes, such as myocardial infarction (MI), lack effective therapies beyond heart transplantation, which is often hindered by donor scarcity and postoperative complications. Human induced pluripotent stem cells (hiPSCs) offer the possibility of myocardial regeneration by differentiating into cardiomyocytes. However, hiPSC-derived cardiomyocytes (hiPSC-cardiomyocytes) exhibit fetal-like calcium flux and energy metabolism, which inhibits their engraftment. Several strategies have been explored to improve the therapeutic efficacy of hiPSC-cardiomyocytes, such as selectively enhancing energy substrate utilization and improving the transplantation environment. In this review, we have discussed the impact of altered mitochondrial biogenesis and metabolic switching on the maturation of hiPSC-cardiomyocytes. Additionally, we have discussed the limitations inherent in current methodologies for assessing metabolism in hiPSC-cardiomyocytes, and the challenges in achieving sufficient metabolic flexibility akin to that in the healthy adult heart.
    Keywords:  Acute coronary syndromes; Energy metabolism; Induced pluripotent stem cells; Maturation; Myocardial infarction; iPSC-cardiomyocytes
    DOI:  https://doi.org/10.1186/s13287-024-03961-4
  12. Biochim Biophys Acta Mol Cell Res. 2024 Oct 07. pii: S0167-4889(24)00203-9. [Epub ahead of print] 119860
    Atrial natriuretic peptide (ANP) modulates stress-induced autophagy in endothelial cells.
    Maurizio Forte, Simona Marchitti, Flavio di Nonno, Donatella Pietrangelo, Rosita Stanzione, Maria Cotugno, Luca D'Ambrosio, Alessandra D'Amico, Vittoria Cammisotto, Gianmarco Sarto, Erica Rocco, Beatrice Simeone, Sonia Schiavon, Daniele Vecchio, Roberto Carnevale, Salvatore Raffa, Giacomo Frati, Massimo Volpe, Sebastiano Sciarretta, Speranza Rubattu.
      Atrial natriuretic peptide (ANP), a cardiac hormone involved in the regulation of water/sodium balance and blood pressure, is also secreted by endothelial cells, where it exerts protective effects in response to stress. Autophagy is an intracellular self-renewal process involved in the degradation of dysfunctional cytoplasmic elements. ANP was recently reported to act as an extracellular regulator of cardiac autophagy. However, its role in the regulation of endothelial autophagy has never been investigated. Here, we tested the effects of ANP in the regulation of autophagy in human umbilical vein endothelial cells (HUVECs). We found that ANP rapidly increases autophagy and autophagic flux at physiological concentrations through its predominant pathway, mediated by natriuretic peptide receptor type A (NPR-A) and protein kinase G (PKG). We further observed that ANP is rapidly secreted by HUVEC under stress conditions, where it mediates stress-induced autophagy through autocrine and paracrine mechanisms. Finally, we found that the protective effects of ANP in response to high-salt loading or tumor necrosis factor (TNF)-α are blunted by concomitant inhibition of autophagy. Overall, our results suggest that ANP acts as an endogenous autophagy activator in endothelial cells. The autophagy mechanism mediates the protective endothelial effects exerted by ANP.
    Keywords:  Atrial natriuretic peptide; Autophagy; Endothelial dysfunction; Endothelial recovery; Natriuretic peptides
    DOI:  https://doi.org/10.1016/j.bbamcr.2024.119860
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