bims-tubesc Biomed News
on Molecular mechanisms in tuberous sclerosis
Issue of 2022‒05‒22
sixteen papers selected by
Marti Cadena Sandoval
metabolic-signalling.eu
  1. The non-essential TSC complex component TBC1D7 restricts tissue mTORC1 signaling and brain and neuron growth.
  2. Genetic analysis of 18 families with tuberous sclerosis complex.
  3. Antiepileptic Effect and Safety Profile of Rapamycin in Pediatric Patients With Tuberous Sclerosis Complex.
  4. Cannabidiol for seizures in tuberous sclerosis complex: Still more questions than answers?
  5. Massive Malignant Epithelioid Angiomyolipoma of the Kidney.
  6. Pilot study evaluating everolimus molecular mechanisms in tuberous sclerosis complex and focal cortical dysplasia.
  7. A Case Report of Tuberous Sclerosis and Autosomal Dominant Polycystic Kidney Disease in the Era of Tolvaptan.
  8. Retinoic acid increases the cellular cholesterol predominantly in a mTOR-independent manner.
  9. Prolonged deprivation of arginine or leucine induces PI3K/Akt-dependent reactivation of mTORC1.
  10. Perineuronal Nets Degradation and Parvalbumin Interneuron loss in a Mouse Model of DEPDC5-related Epilepsy.
  11. mTOR substrate phosphorylation in growth control.
  12. mTORC2 mediates structural plasticity in distal nociceptive endings that contributes to pain hypersensitivity following inflammation.
  13. Translation initiation factor eIF3a regulates glucose metabolism and cell proliferation via promoting small GTPase Rheb synthesis and AMPK activation.
  14. Sirolimus as a promising drug therapy for blue rubber bleb nevus syndrome: Two-case report.
  15. Aspartate metabolism in endothelial cells activates the mTORC1 pathway to initiate translation during angiogenesis.
  16. The lysosomal V-ATPase a3 subunit is involved in localization of Mon1-Ccz1, the GEF for Rab7, to secretory lysosomes in osteoclasts.
  1. Cell Rep. 2022 May 17. pii: S2211-1247(22)00595-2. [Epub ahead of print]39(7): 110824
    The non-essential TSC complex component TBC1D7 restricts tissue mTORC1 signaling and brain and neuron growth.
    Sandra Schrötter, Christopher J Yuskaitis, Michael R MacArthur, Sarah J Mitchell, Aaron M Hosios, Maria Osipovich, Margaret E Torrence, James R Mitchell, Gerta Hoxhaj, Mustafa Sahin, Brendan D Manning.
      The tuberous sclerosis complex (TSC) 1 and 2 proteins associate with TBC1D7 to form the TSC complex, which is an essential suppressor of mTOR complex 1 (mTORC1), a ubiquitous driver of cell and tissue growth. Loss-of-function mutations in TSC1 or TSC2, but not TBC1D7, give rise to TSC, a pleiotropic disorder with aberrant activation of mTORC1 in various tissues. Here, we characterize mice with genetic deletion of Tbc1d7, which are viable with normal growth and development. Consistent with partial loss of function of the TSC complex, Tbc1d7 knockout (KO) mice display variable increases in tissue mTORC1 signaling with increased muscle fiber size but with strength and motor defects. Their most pronounced phenotype is brain overgrowth due to thickening of the cerebral cortex, with enhanced neuron-intrinsic mTORC1 signaling and growth. Thus, TBC1D7 is required for full TSC complex function in tissues, and the brain is particularly sensitive to its growth-suppressing activities.
    Keywords:  CP: Developmental biology; CP: Neuroscience; TBC1D7; Tsc1; Tsc2; brain; gait; growth; hamartin; mTOR; megalencephaly; mouse model; neurons; rapamycin; tuberin; tuberous sclerosis complex
    DOI:  https://doi.org/10.1016/j.celrep.2022.110824
  2. Neurogenetics. 2022 May 21.
    Genetic analysis of 18 families with tuberous sclerosis complex.
    Kaili Yin, Nan Lin, Qiang Lu, Liri Jin, Yan Huang, Xiangqin Zhou, Kaifeng Xu, Qing Liu, Xue Zhang.
      Tuberous sclerosis complex (TSC) is mainly caused by variants in TSC1 and TSC2, which encodes hamartin protein and tuberin protein, respectively. Here, we report clinical and molecular characteristics of 18 families with TSC. High-throughput DNA sequencing was employed to detect variants in all the exons and flanking region of TSC1 and TSC2. TA clone and real-time PCR were performed to verify the pathogenicity of candidate variants. A total of 17 mutations were identified, including 13 mutations in TSC2 and 4 mutations in TSC1. Fifty-six percent (10/18) of the families carried de novo mutations, and 8 of these mutations were not reported previously. Most mutations detected were loss-of-function mutations (15/17). One splice-site mutation (TSC2 c.599 + 5G > A) caused abnormal splicing and was confirmed by in vitro analysis. Facial angiofibromas (94%) and epilepsy (89%) were the most prevalent clinical features in our patients. Treatment with anti-seizure medication (ASM) or in combination with rapamycin results in clinical remission in most patients with TSC-associated seizures (14/15). For genotype-phenotype correlation, patients in our cohort with TSC2 mutations had an earlier onset age and patients with TSC1 showed better response to ASM. Our study has expanded the spectrum of TSC1 and TSC2 causing TSC.
    Keywords:  Mutation; TSC1; TSC2; Tuberous sclerosis complex
    DOI:  https://doi.org/10.1007/s10048-022-00694-5
  3. Front Neurol. 2022 ;13 704978
    Antiepileptic Effect and Safety Profile of Rapamycin in Pediatric Patients With Tuberous Sclerosis Complex.
    Krzysztof Sadowski, Kamil Sijko, Dorota Domańska-Pakieła, Julita Borkowska, Dariusz Chmielewski, Agata Ulatowska, Sergiusz Józwiak, Katarzyna Kotulska.
      Background: Epilepsy develops in 70-90% of children with Tuberous Sclerosis Complex (TSC) and is often resistant to medication. Treatment with mTOR pathway inhibitors is an important therapeutic option in drug-resistant epilepsy associated with TSC. Our study evaluated the antiepileptic effect of rapamycin in the pediatric population of patients diagnosed with TSC.Methods: This single center, open-label study evaluated safety and anti-epileptic efficacy of 12 months of rapamycin treatment in 32 patients aged from 11 months to 14 years with drug-resistant TSC- associated epilepsy.
    Results: After the first 6 months of treatment, the improvement in seizure frequency, defined as at least a 50% reduction in the number of seizures per week compared to baseline, was seen in 18 individuals (56.25%). We observed no change in 12 individuals (37.5%) and worsening, defined as increase in the number of seizures-in 2 patients (6.25%). The overall improvement defined as at least a 50% reduction in seizure frequency was found in 65.6% of all patients after 12 months with 28% of patients obtaining complete remission. Another five patients experienced at least an 80% reduction in the frequency of seizures. Concomitant treatment with vigabatrin, and to a much lesser extent topiramate and levetiracetam, was an additional favorable prognostic factor for the success of the therapy. A linear relationship between the cumulative dose of rapamycin and its therapeutic effect was observed. The safety profile of the drug was satisfactory. In none of the observed cases did the adverse events reach the level that required withdrawal of the rapamycin treatment. The reason for dropouts was insufficient drug efficacy in 3 cases.
    Conclusions: Long-term use of rapamycin, especially in combination with vigabatrin, might be a beneficial therapeutic option in the treatment of drug-resistant epilepsy in children with TSC.
    Keywords:  epilepsy; mTOR inhibitors; rapamycin; sirolimus; tuberous sclerosis
    DOI:  https://doi.org/10.3389/fneur.2022.704978
  4. Epilepsy Behav. 2022 May 14. pii: S1525-5050(22)00150-0. [Epub ahead of print] 108701
    Cannabidiol for seizures in tuberous sclerosis complex: Still more questions than answers?
    Francesco Brigo, Sasha Olivo.
      
    Keywords:  Cannabidiol; Clobazam; Efficacy; Seizures; Tuberous sclerosis
    DOI:  https://doi.org/10.1016/j.yebeh.2022.108701
  5. J Kidney Cancer VHL. 2022 ;9(2): 13-18
    Massive Malignant Epithelioid Angiomyolipoma of the Kidney.
    Isaac M Tessone, Benjamin Lichtbroun, Arnav Srivastava, Alexandra L Tabakin, Charles F Polotti, Roman Groisberg, Evita Sadimin, Eric A Singer, Miral S Grandhi.
      Renal angiomyolipomas (AMLs) are a subset of perivascular epithelioid cell neoplasms (PEComas) that are associated with tuberous sclerosis complex (TSC). Epithelioid angiomyolipomas (EAMLs) are a rare variant of AML with more aggressive propensities. EAMLs with malignant potential can be difficult to distinguish from relatively benign AMLs and other renal tumors. Although there are no established criteria for predicting EAML malignancy, there are proposed histologic parameters that are associated with higher tumor risk. EAML can be treated with surgical resection as well as mTOR inhibitors. Here, we present a unique case of a patient with a 36-cm renal EAML metastatic to the lungs that was treated with complete surgical resection of the primary lesion and mTOR inhibition.
    Keywords:  PEComa; epithelioid angiomyolipoma; mTOR inhibitor; renal tumor; tuberous sclerosis
    DOI:  https://doi.org/10.15586/jkcvhl.v9i2.210
  6. PLoS One. 2022 ;17(5): e0268597
    Pilot study evaluating everolimus molecular mechanisms in tuberous sclerosis complex and focal cortical dysplasia.
    Dominique F Leitner, Evgeny Kanshin, Manor Askenazi, Yik Siu, Daniel Friedman, Sasha Devore, Drew Jones, Beatrix Ueberheide, Thomas Wisniewski, Orrin Devinsky.
      BACKGROUND: Tuberous sclerosis complex (TSC) and some focal cortical dysplasias (FCDs) are associated with dysfunctional mTOR signaling, resulting in increased cell growth and ribosomal S6 protein phosphorylation (phospho-S6). mTOR inhibitors can reduce TSC tumor growth and seizure frequency, and preclinical FCD studies indicate seizure suppression. This pilot study evaluated safety of mTOR inhibitor everolimus in treatment resistant (failure of >2 anti-seizure medications) TSC and FCD patients undergoing surgical resection and to assess mTOR signaling and molecular pathways.METHODS AND FINDINGS: We evaluated everolimus in 14 treatment resistant epilepsy patients undergoing surgical resection (4.5 mg/m2 daily for 7 days; n = 4 Active, mean age 18.3 years, range 4-26; n = 10, Control, mean age 13.1, range 3-45). Everolimus was well tolerated. Mean plasma everolimus in Active participants were in target range (12.4 ng/ml). Brain phospho-S6 was similar in Active and Control participants with a lower trend in Active participants, with Ser235/236 1.19-fold (p = 0.67) and Ser240/244 1.15-fold lower (p = 0.66). Histologically, Ser235/236 was 1.56-fold (p = 0.37) and Ser240/244 was 5.55-fold lower (p = 0.22). Brain proteomics identified 11 proteins at <15% false discovery rate associated with coagulation system (p = 1.45x10-9) and acute phase response (p = 1.23x10-6) activation. A weighted gene correlation network analysis (WGCNA) of brain proteomics and phospho-S6 identified 5 significant modules. Higher phospho-S6 correlated negatively with cellular respiration and synaptic transmission and positively with organophosphate metabolic process, nuclear mRNA catabolic process, and neuron ensheathment. Brain metabolomics identified 14 increased features in Active participants, including N-acetylaspartylglutamic acid. Plasma proteomics and cytokine analyses revealed no differences.
    CONCLUSIONS: Short-term everolimus before epilepsy surgery in TSC and FCD resulted in no adverse events and trending lower mTOR signaling (phospho-S6). Future studies should evaluate implications of our findings, including coagulation system activation and everolimus efficacy in FCD, in larger studies with long-term treatment to better understand molecular and clinical effects.
    CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov NCT02451696.
    DOI:  https://doi.org/10.1371/journal.pone.0268597
  7. Curr Rev Clin Exp Pharmacol. 2022 May 17.
    A Case Report of Tuberous Sclerosis and Autosomal Dominant Polycystic Kidney Disease in the Era of Tolvaptan.
    Xavier E Guerra-Torres.
      BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) may coexist with other genetic disorders, such as tuberous sclerosis, when deletion in TSC2/PKD1 genes occurs. Recently, the effect of tolvaptan has been explored in ADPKD patients alone, but its safety and efficacy on TSC2/PKD1 contiguous gene syndrome is unknown.CASE PRESENTATION: This report describes the case of an asymptomatic patient with TSC2/PKD1 contiguous gene syndrome that fulfills the imaging criteria for initiating the treatment with tolvaptan. After twelve months, the patient did not exhibit severe adverse effects and blood pressure control improved.
    CONCLUSION: In this TSC2/PKD1 contiguous gene syndrome single case report, tolvaptan was safe and well-tolerated. More extensive experimental studies are needed to deeply understand the therapeutic implications of vasopressin V2-receptor inhibition in the TSC2/PKD1 contiguous gene syndrome patients.
    Keywords:  Autosomal dominant polycystic kidney disease; TSC2/PKD1 contiguous gene syndrome; tolvaptan; tuberous sclerosis; tuberous sclerosis complex; vasopressin antagonist
    DOI:  https://doi.org/10.2174/2772432817666220517162012
  8. Immunol Res. 2022 May 18.
    Retinoic acid increases the cellular cholesterol predominantly in a mTOR-independent manner.
    Satya Prakash, Ambak Kumar Rai.
      Retinoic acid (RA) plays a role in the mounting immune response and controls several functions of the human body, including cholesterol homeostasis. The synthesis, uptake, and efflux of cellular cholesterol are significantly linked to the mammalian target of rapamycin complex-1 (mTORC1). Activation of mTORC1 promotes the synthesis and uptake of the cholesterol and suppresses its efflux, thus causing accumulation of cellular cholesterol. It is intriguing to know the effect of a high dose of RA on cholesterol accumulation in macrophages (mφ) and whether it is via mTOR activation. It is important to note that the long-term treatment of RA in humans is safe. Therefore, we chose a high dose of RA to observe its effect, which may be implicated in diseases like visceral leishmaniasis, where cholesterol deficiency is established. In the present study, we found the increased expression of RAPTOR, a regulatory component of the mTORC1 complex, in mφ upon treatment with RA. We observed the increased expression of SREBP2, LDLR, and PCSK9 in RA-treated mφ under sufficient cholesterol conditions, which further increased cellular cholesterol levels. Notably, their expressions were decreased when the mTOR pathway was inhibited by rapamycin. However, treatment with rapamycin did not result in the loss of cellular cholesterol in RA-treated mφ. Comparison with rapamycin-treated mφ suggests that RA induces cellular cholesterol levels in a mTORC1-independent manner.
    Keywords:  Cholesterol; Macrophage; Retinoic acid (RA); mTOR
    DOI:  https://doi.org/10.1007/s12026-022-09292-x
  9. J Biol Chem. 2022 May 13. pii: S0021-9258(22)00470-7. [Epub ahead of print] 102030
    Prolonged deprivation of arginine or leucine induces PI3K/Akt-dependent reactivation of mTORC1.
    Gwen R Buel, Huy Dang, John M Asara, John Blenis, Anders P Mutvei.
      The mechanistic target of rapamycin complex 1 (mTORC1) is a serine/threonine kinase complex that promotes anabolic processes including protein, lipid, and nucleotide synthesis, while suppressing catabolic processes such as macroautophagy. mTORC1 activity is regulated by growth factors and amino acids which signal through distinct but integrated molecular pathways: growth factors largely signal through the PI3K/Akt-dependent pathway, whereas the availabilities of amino acids leucine and arginine are communicated to mTORC1 by the Rag-GTPase pathway. While it is relatively well described how acute changes in leucine and arginine levels affect mTORC1 signaling, the effects of prolonged amino acid deprivation remain less well understood. Here, we demonstrate that prolonged deprivation of arginine and/or leucine leads to reactivation of mTORC1 activity, which reaches activation levels similar to those observed in nutrient-rich conditions. Surprisingly, we find that this reactivation is independent of the regeneration of amino acids by canonical autophagy or proteasomal degradation, but is dependent on PI3K/Akt signaling. Together, our data identify a novel crosstalk between the amino acid and PI3K/Akt signaling pathways upstream of mTORC1. These observations extend our understanding of the role of mTORC1 in growth-related diseases and indicate that dietary intervention by removal of leucine and/or arginine may be an ineffective therapeutic approach.
    DOI:  https://doi.org/10.1016/j.jbc.2022.102030
  10. Dev Neurosci. 2022 May 17.
    Perineuronal Nets Degradation and Parvalbumin Interneuron loss in a Mouse Model of DEPDC5-related Epilepsy.
    Tao Yang, Shuntong Hu, Wei-Chih Chang, Hsin-Yi Kao, Yu Wang.
      DEPDC5, the key gene within the mechanistic target of rapamycin (mTOR) pathway, is one of the most common causative genes in patients with epilepsy and malformation of cortical development (MCD). Although somatic mutations in the dorsal cortical progenitors generate the malformed cortex, its pathogenesis of hyperexcitability is complex and remains unclear. We specifically deleted Depdc5 in the mouse forebrain dorsal progenitors to model DEPDC5-related epilepsy, and investigated whether and how parvalbumin interneurons were non-cell autonomously affected in the malformed cortex. We showed that long before seizures, coincident with microglia inflammation, proteolytic enzymes degraded perineuronal nets (PNN) in the malformed cortex, resulting in parvalbumin (PV+) interneuron loss and presynaptic inhibition impairment. Our studies therefore uncovered the hitherto unknown role of PNN in mTOR-related MCD, providing a new framework for mechanistic-based therapeutic development.
    DOI:  https://doi.org/10.1159/000525039
  11. Cell. 2022 May 12. pii: S0092-8674(22)00460-3. [Epub ahead of print]
    mTOR substrate phosphorylation in growth control.
    Stefania Battaglioni, Don Benjamin, Matthias Wälchli, Timm Maier, Michael N Hall.
      The target of rapamycin (TOR), discovered 30 years ago, is a highly conserved serine/threonine protein kinase that plays a central role in regulating cell growth and metabolism. It is activated by nutrients, growth factors, and cellular energy. TOR forms two structurally and functionally distinct complexes, TORC1 and TORC2. TOR signaling activates cell growth, defined as an increase in biomass, by stimulating anabolic metabolism while inhibiting catabolic processes. With emphasis on mammalian TOR (mTOR), we comprehensively reviewed the literature and identified all reported direct substrates. In the context of recent structural information, we discuss how mTORC1 and mTORC2, despite having a common catalytic subunit, phosphorylate distinct substrates. We conclude that the two complexes recruit different substrates to phosphorylate a common, minimal motif.
    DOI:  https://doi.org/10.1016/j.cell.2022.04.013
  12. J Clin Invest. 2022 May 17. pii: e152635. [Epub ahead of print]
    mTORC2 mediates structural plasticity in distal nociceptive endings that contributes to pain hypersensitivity following inflammation.
    Calvin Wong, Omer Barkai, Feng Wang, Carolina Thörn Pérez, Shaya Lev, Weihua Cai, Shannon Tansley, Noosha Yousefpour, Mehdi Hooshmandi, Kevin C Lister, Mariam Latif, A Claudio Cuello, Masha Prager-Khoutorsky, Jeffrey S Mogil, Philippe Séguéla, Yves De Koninck, Alfredo Ribeiro-da-Silva, Alexander M Binshtok, Arkady Khoutorsky.
      The encoding of noxious stimuli into action potential firing is largely mediated by nociceptive free nerve endings. Tissue inflammation, by changing the intrinsic properties of the nociceptive endings, leads to nociceptive hyperexcitability, and thus to the development of inflammatory pain. Here, we showed that tissue inflammation-induced activation of the mammalian target of rapamycin complex 2 (mTORC2) triggers changes in the architecture of nociceptive terminals and leads to inflammatory pain. Pharmacological activation of mTORC2 induced elongation and branching of nociceptor peripheral endings and caused long-lasting pain hypersensitivity. Conversely, nociceptor-specific deletion of the mTORC2 regulatory protein, Rictor, prevented inflammation-induced elongation and branching of cutaneous nociceptive fibers and attenuated inflammatory pain hypersensitivity. Computational modelling demonstrated that mTORC2-mediated structural changes in the nociceptive terminal tree are sufficient to increase the excitability of nociceptors. Targeting mTORC2 using a single injection of antisense oligonucleotide against Rictor provided long-lasting alleviation of inflammatory pain hypersensitivity. Collectively, we showed that tissue inflammation-induced activation of mTORC2 causes structural plasticity of nociceptive free nerve endings in the epidermis and inflammatory hyperalgesia, representing a therapeutic target for inflammatory pain.
    Keywords:  Mouse models; Neuroscience; Pain; Signal transduction
    DOI:  https://doi.org/10.1172/JCI152635
  13. J Biol Chem. 2022 May 17. pii: S0021-9258(22)00484-7. [Epub ahead of print] 102044
    Translation initiation factor eIF3a regulates glucose metabolism and cell proliferation via promoting small GTPase Rheb synthesis and AMPK activation.
    Shijie Ma, Zizheng Dong, Yanfei Huang, Jing-Yuan Liu, Jian-Ting Zhang.
      eIF3a, the largest subunit of eukaryotic initiation factor 3 (eIF3) complex, has been shown to be overexpressed in malignant cancer cells, potentially making it a proto-oncogene. eIF3a overexpression can drive cancer cell proliferation but contributes to better prognosis. While its contribution to prognosis was previously shown to be due to its function in suppressing synthesis of DNA damage repair proteins, it remains unclear how eIF3a regulates cancer cell proliferation. In this study, we show using genetic approaches that eIF3a controls cell proliferation by regulating glucose metabolism via the phosphorylation and activation of AMPKα at Thr172 in its kinase activation loop. We demonstrate that eIF3a regulates AMPK activation mainly by controlling synthesis of the small GTPase Rheb, largely independent of the well-known AMPK upstream kinases LKB1 and CaMKK2, and also independent of mTOR signaling and glucose levels. Our findings suggest that glucose metabolism in and proliferation of cancer cells may be translationally regulated via a novel eIF3a-Rheb-AMPK signaling axis.
    Keywords:  AMPK; Rheb; cell proliferation; eIF3a; glucose metabolism; protein synthesis
    DOI:  https://doi.org/10.1016/j.jbc.2022.102044
  14. SAGE Open Med Case Rep. 2022 ;10 2050313X221097755
    Sirolimus as a promising drug therapy for blue rubber bleb nevus syndrome: Two-case report.
    Jian-Xun Ma, You-Chen Xia, Li-Ping Zou, Heng-Ju Lin, Xu Chang, Li-Ying Liu, Joy Roechelle A Toledo.
      Blue rubber bleb nevus syndrome is a very rare systemic vascular malformation frequently affecting the skin and the gastrointestinal tract. The pathogenesis of the disease is still unclear, and the standard treatment does not exist. This study reports two blue rubber bleb nevus syndrome cases, of which the second patient received the TEK gene mutations detection and got a low-dose sirolimus therapy, compared with the first patient who was not treated with sirolimus. The report shows some positive findings of TEK gene mutations and the efficacy of sirolimus treatment. We postulate that the TEK gene mutations play an important role in the pathogenesis. The mutations of different locations of the TEK gene cause a wide range of activating TIE2 mutations, which could stimulate the mammalian target of rapamycin signaling pathways to mediate angiogenesis, resulting in different clinical phenotypes of cutaneomucosal venous malformations. Sirolimus could effectively block the upstream and downstream factors of mammalian target of rapamycin signaling pathways to achieve the antiangiogenic effect. The initial dose of sirolimus can be 0.05-0.1 mg/kg/d for a trough level of 5-15 μg/L in the treatment of blue rubber bleb nevus syndrome. However, a lower-dose sirolimus is also effective while minimizing the side effects.
    Keywords:  Blue rubber bleb nevus syndrome; TEK gene mutations; mTOR; sirolimus
    DOI:  https://doi.org/10.1177/2050313X221097755
  15. Dev Cell. 2022 May 11. pii: S1534-5807(22)00286-6. [Epub ahead of print]
    Aspartate metabolism in endothelial cells activates the mTORC1 pathway to initiate translation during angiogenesis.
    Roxana E Oberkersch, Giovanna Pontarin, Matteo Astone, Marianna Spizzotin, Liaisan Arslanbaeva, Giovanni Tosi, Emiliano Panieri, Sara Ricciardi, Maria Francesca Allega, Alessia Brossa, Paolo Grumati, Benedetta Bussolati, Stefano Biffo, Saverio Tardito, Massimo M Santoro.
      Angiogenesis, the active formation of new blood vessels from pre-existing ones, is a complex and demanding biological process that plays an important role in physiological as well as pathological settings. Recent evidence supports cell metabolism as a critical regulator of angiogenesis. However, whether and how cell metabolism regulates endothelial growth factor receptor levels and nucleotide synthesis remains elusive. We here shown in both human cell lines and mouse models that during developmental and pathological angiogenesis, endothelial cells (ECs) use glutaminolysis-derived glutamate to produce aspartate (Asp) via aspartate aminotransferase (AST/GOT). Asp leads to mTORC1 activation which, in turn, regulates endothelial translation machinery for VEGFR2 and FGFR1 synthesis. Asp-dependent mTORC1 pathway activation also regulates de novo pyrimidine synthesis in angiogenic ECs. These findings identify glutaminolysis-derived Asp as a regulator of mTORC1-dependent endothelial translation and pyrimidine synthesis. Our studies may help overcome anti-VEGF therapy resistance by targeting endothelial growth factor receptor translation.
    Keywords:  angiogenesis; aspartate metabolism; endothelial metabolism; mTOR signalling; tumor angiogenesis
    DOI:  https://doi.org/10.1016/j.devcel.2022.04.018
  16. Sci Rep. 2022 May 19. 12(1): 8455
    The lysosomal V-ATPase a3 subunit is involved in localization of Mon1-Ccz1, the GEF for Rab7, to secretory lysosomes in osteoclasts.
    Naomi Matsumoto, Mizuki Sekiya, Ge-Hong Sun-Wada, Yoh Wada, Mayumi Nakanishi-Matsui.
      We have shown previously that the lysosomal a3 isoform of the a subunit of vacuolar-type ATPase (V-ATPase) interacts with inactive (GDP-bound form) Rab7, a small GTPase that regulates late endosome/lysosome trafficking, and that a3 recruits Rab7 to secretory lysosomes in mouse osteoclasts. This is essential for outward trafficking of secretory lysosomes and thus for bone resorption. However, the molecular mechanism underlying the recruitment of Rab7 by a3 remains to be fully elucidated. Here, we showed that a3 interacts with the Mon1A-Ccz1 complex, a guanine nucleotide exchange factor (GEF) for Rab7, using HEK293T cells. The interaction was mediated by the amino-terminal half domain of a3 and the longin motifs of Mon1A and Ccz1. Exogenous expression of the GEF promoted the interaction between a3 and Rab7. Mon1A mutants that interact inefficiently with Rab7 interacted with a3 at a similar level to wild-type Mon1A. Lysosomal localization of endogenous Ccz1 was abolished in osteoclasts lacking a3. These results suggest that the lysosomal a3 isoform of V-ATPase interacts with Mon1A-Ccz1, and that a3 is important for Mon1A-Ccz1 localization to secretory lysosomes, which mediates Rab7 recruitment to the organelle.
    DOI:  https://doi.org/10.1038/s41598-022-12397-w
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