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Nature Neuroscience Dec 2023It is generally thought that under basal conditions, neurons produce ATP mainly through mitochondrial oxidative phosphorylation (OXPHOS), and glycolytic activity only...
It is generally thought that under basal conditions, neurons produce ATP mainly through mitochondrial oxidative phosphorylation (OXPHOS), and glycolytic activity only predominates when neurons are activated and need to meet higher energy demands. However, it remains unknown whether there are differences in glucose metabolism between neuronal somata and axon terminals. Here, we demonstrated that neuronal somata perform higher levels of aerobic glycolysis and lower levels of OXPHOS than terminals, both during basal and activated states. We found that the glycolytic enzyme pyruvate kinase 2 (PKM2) is localized predominantly in the somata rather than in the terminals. Deletion of Pkm2 in mice results in a switch from aerobic glycolysis to OXPHOS in neuronal somata, leading to oxidative damage and progressive loss of dopaminergic neurons. Our findings update the conventional view that neurons uniformly use OXPHOS under basal conditions and highlight the important role of somatic aerobic glycolysis in maintaining antioxidant capacity.
Topics: Animals; Mice; Oxidative Phosphorylation; Glycolysis; Phosphotransferases; Oxidative Stress; Glucose
PubMed: 37996529
DOI: 10.1038/s41593-023-01476-4 -
Science (New York, N.Y.) Jan 2022Fertilization of an egg by multiple sperm (polyspermy) leads to lethal genome imbalance and chromosome segregation defects. In , the block to polyspermy is facilitated...
Fertilization of an egg by multiple sperm (polyspermy) leads to lethal genome imbalance and chromosome segregation defects. In , the block to polyspermy is facilitated by a mechanism that prevents polytubey (the arrival of multiple pollen tubes to one ovule). We show here that FERONIA, ANJEA, and HERCULES RECEPTOR KINASE 1 receptor-like kinases located at the septum interact with pollen tube-specific RALF6, 7, 16, 36, and 37 peptide ligands to establish this polytubey block. The same combination of RALF (rapid alkalinization factor) peptides and receptor complexes controls pollen tube reception and rupture inside the targeted ovule. Pollen tube rupture releases the polytubey block at the septum, which allows the emergence of secondary pollen tubes upon fertilization failure. Thus, orchestrated steps in the fertilization process in are coordinated by the same signaling components to guarantee and optimize reproductive success.
Topics: Arabidopsis; Arabidopsis Proteins; Fertilization; Ligands; Ovule; Peptides; Phosphotransferases; Pollen; Pollen Tube; Pollination; Protein Kinases; Signal Transduction
PubMed: 35050671
DOI: 10.1126/science.abl4683 -
Cell Sep 2020Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of familial Parkinson's disease. LRRK2 is a multi-domain protein containing a kinase and...
Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of familial Parkinson's disease. LRRK2 is a multi-domain protein containing a kinase and GTPase. Using correlative light and electron microscopy, in situ cryo-electron tomography, and subtomogram analysis, we reveal a 14-Å structure of LRRK2 bearing a pathogenic mutation that oligomerizes as a right-handed double helix around microtubules, which are left-handed. Using integrative modeling, we determine the architecture of LRRK2, showing that the GTPase and kinase are in close proximity, with the GTPase closer to the microtubule surface, whereas the kinase is exposed to the cytoplasm. We identify two oligomerization interfaces mediated by non-catalytic domains. Mutation of one of these abolishes LRRK2 microtubule-association. Our work demonstrates the power of cryo-electron tomography to generate models of previously unsolved structures in their cellular environment.
Topics: Cryoelectron Microscopy; Cytoplasm; Electron Microscope Tomography; GTP Phosphohydrolases; HEK293 Cells; Humans; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; Microscopy, Electron, Transmission; Microtubules; Models, Chemical; Mutation; Parkinson Disease; Phosphotransferases; Protein Domains; WD40 Repeats
PubMed: 32783917
DOI: 10.1016/j.cell.2020.08.004 -
Nature Communications Feb 2022Aging and mechanical overload are prominent risk factors for osteoarthritis (OA), which lead to an imbalance in redox homeostasis. The resulting state of oxidative...
Aging and mechanical overload are prominent risk factors for osteoarthritis (OA), which lead to an imbalance in redox homeostasis. The resulting state of oxidative stress drives the pathological transition of chondrocytes during OA development. However, the specific molecular pathways involved in disrupting chondrocyte redox homeostasis remain unclear. Here, we show that selenophosphate synthetase 1 (SEPHS1) expression is downregulated in human and mouse OA cartilage. SEPHS1 downregulation impairs the cellular capacity to synthesize a class of selenoproteins with oxidoreductase functions in chondrocytes, thereby elevating the level of reactive oxygen species (ROS) and facilitating chondrocyte senescence. Cartilage-specific Sephs1 knockout in adult mice causes aging-associated OA, and augments post-traumatic OA, which is rescued by supplementation of N-acetylcysteine (NAC). Selenium-deficient feeding and Sephs1 knockout have synergistic effects in exacerbating OA pathogenesis in mice. Therefore, we propose that SEPHS1 is an essential regulator of selenium metabolism and redox homeostasis, and its dysregulation governs the progression of OA.
Topics: Aging; Animals; Cartilage, Articular; Chondrocytes; Disease Models, Animal; Homeostasis; Male; Mice; Mice, Knockout; Osteoarthritis; Oxidation-Reduction; Oxidative Stress; Phosphotransferases; Reactive Oxygen Species; Selenium; Selenoproteins; Transcriptome
PubMed: 35140209
DOI: 10.1038/s41467-022-28385-7 -
Nature Dec 2021The liberation of energy stores from adipocytes is critical to support survival in times of energy deficit; however, uncontrolled or chronic lipolysis associated with...
The liberation of energy stores from adipocytes is critical to support survival in times of energy deficit; however, uncontrolled or chronic lipolysis associated with insulin resistance and/or insulin insufficiency disrupts metabolic homeostasis. Coupled to lipolysis is the release of a recently identified hormone, fatty-acid-binding protein 4 (FABP4). Although circulating FABP4 levels have been strongly associated with cardiometabolic diseases in both preclinical models and humans, no mechanism of action has yet been described. Here we show that hormonal FABP4 forms a functional hormone complex with adenosine kinase (ADK) and nucleoside diphosphate kinase (NDPK) to regulate extracellular ATP and ADP levels. We identify a substantial effect of this hormone on beta cells and given the central role of beta-cell function in both the control of lipolysis and development of diabetes, postulate that hormonal FABP4 is a key regulator of an adipose-beta-cell endocrine axis. Antibody-mediated targeting of this hormone complex improves metabolic outcomes, enhances beta-cell function and preserves beta-cell integrity to prevent both type 1 and type 2 diabetes. Thus, the FABP4-ADK-NDPK complex, Fabkin, represents a previously unknown hormone and mechanism of action that integrates energy status with the function of metabolic organs, and represents a promising target against metabolic disease.
Topics: Adipocytes; Diabetes Mellitus; Fatty Acid-Binding Proteins; Humans; Insulin; Islets of Langerhans; Lipolysis; Nucleosides; Phosphotransferases
PubMed: 34880500
DOI: 10.1038/s41586-021-04137-3 -
Nature Metabolism Sep 2020The mechanistic target of rapamycin complex 1 (mTORC1) kinase regulates cell growth by setting the balance between anabolic and catabolic processes. To be active, mTORC1...
The mechanistic target of rapamycin complex 1 (mTORC1) kinase regulates cell growth by setting the balance between anabolic and catabolic processes. To be active, mTORC1 requires the environmental presence of amino acids and glucose. While a mechanistic understanding of amino acid sensing by mTORC1 is emerging, how glucose activates mTORC1 remains mysterious. Here, we used metabolically engineered human cells lacking the canonical energy sensor AMP-activated protein kinase to identify glucose-derived metabolites required to activate mTORC1 independent of energetic stress. We show that mTORC1 senses a metabolite downstream of the aldolase and upstream of the GAPDH-catalysed steps of glycolysis and pinpoint dihydroxyacetone phosphate (DHAP) as the key molecule. In cells expressing a triose kinase, the synthesis of DHAP from DHA is sufficient to activate mTORC1 even in the absence of glucose. DHAP is a precursor for lipid synthesis, a process under the control of mTORC1, which provides a potential rationale for the sensing of DHAP by mTORC1.
Topics: AMP-Activated Protein Kinases; Dihydroxyacetone; Dihydroxyacetone Phosphate; Energy Metabolism; Fructose-Bisphosphate Aldolase; Glucose; Glycolysis; HEK293 Cells; Humans; Lipid Metabolism; Phosphotransferases (Alcohol Group Acceptor); TOR Serine-Threonine Kinases
PubMed: 32719541
DOI: 10.1038/s42255-020-0250-5 -
Cell Jan 2024The FERONIA (FER)-LLG1 co-receptor and its peptide ligand RALF regulate myriad processes for plant growth and survival. Focusing on signal-induced cell surface...
The FERONIA (FER)-LLG1 co-receptor and its peptide ligand RALF regulate myriad processes for plant growth and survival. Focusing on signal-induced cell surface responses, we discovered that intrinsically disordered RALF triggers clustering and endocytosis of its cognate receptors and FER- and LLG1-dependent endocytosis of non-cognate regulators of diverse processes, thus capable of broadly impacting downstream responses. RALF, however, remains extracellular. We demonstrate that RALF binds the cell wall polysaccharide pectin. They phase separate and recruit FER and LLG1 into pectin-RALF-FER-LLG1 condensates to initiate RALF-triggered cell surface responses. We show further that two frequently encountered environmental challenges, elevated salt and temperature, trigger RALF-pectin phase separation, promiscuous receptor clustering and massive endocytosis, and that this process is crucial for recovery from stress-induced growth attenuation. Our results support that RALF-pectin phase separation mediates an exoskeletal mechanism to broadly activate FER-LLG1-dependent cell surface responses to mediate the global role of FER in plant growth and survival.
Topics: Phosphotransferases; Arabidopsis Proteins; Arabidopsis; Pectins; Phase Separation; GPI-Linked Proteins
PubMed: 38157854
DOI: 10.1016/j.cell.2023.11.038 -
Molecular Genetics and Metabolism Nov 2022Studies aimed at supporting different treatment approaches for pantothenate kinase-associated neurodegeneration (PKAN) have revealed the complexity of coenzyme A (CoA)... (Review)
Review
Studies aimed at supporting different treatment approaches for pantothenate kinase-associated neurodegeneration (PKAN) have revealed the complexity of coenzyme A (CoA) metabolism and the limits of our current knowledge about disease pathogenesis. Here we offer a foundation for critically evaluating the myriad approaches, argue for the importance of unbiased disease models, and highlight some of the outstanding questions that are central to our understanding and treating PKAN.
Topics: Humans; Pantothenate Kinase-Associated Neurodegeneration; Coenzyme A; Phosphotransferases (Alcohol Group Acceptor)
PubMed: 36240582
DOI: 10.1016/j.ymgme.2022.09.011 -
Biochemical Pharmacology Jan 2022Dictamnine (Dic), a naturally occurring small-molecule furoquinoline alkaloid isolated from the root bark of Dictamnus dasycarpus Turcz., is reported to display...
Dictamnine (Dic), a naturally occurring small-molecule furoquinoline alkaloid isolated from the root bark of Dictamnus dasycarpus Turcz., is reported to display anticancer properties. However, little is known about the direct target proteins and anticancer mechanisms of Dic. In the current study, Dic was found to suppress the growth of lung cancer cells in vitro and in vivo, and to attenuate the activation of PI3K/AKT/mTOR and mitogen-activated protein kinase (MAPK) signaling pathways by inhibiting the phosphorylation and activation of receptor tyrosine kinase c-Met. Moreover, the binding of Dic to c-Met was confirmed by using cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) assay. Among all cancer cell lines tested, Dic inhibited the proliferation of c-Met-dependent EBC-1 cells with the greatest potency (IC = 2.811 μM). Notably, Dic was shown to synergistically improve the chemo-sensitivity of epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-resistant lung cancer cells to gefitinib and osimertinib. These results suggest that Dic is a c-Met inhibitor that can serve as a potential therapeutic agent in the treatment of lung cancer, especially against EGFR TKI-resistant and c-Met-dependent lung cancer.
Topics: A549 Cells; Animals; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Female; Hep G2 Cells; Humans; Lung Neoplasms; MAP Kinase Signaling System; Mice, Inbred BALB C; Mice, Nude; Phosphatidylinositol 3-Kinases; Phosphotransferases; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-met; Quinolines; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays; Mice
PubMed: 34861243
DOI: 10.1016/j.bcp.2021.114864 -
Advances in Experimental Medicine and... 2021Bacteria are able to inhabit and survive vastly diverse environments. This enormous adaptive capacity depend on their ability to perceive cues from the micro-environment...
Bacteria are able to inhabit and survive vastly diverse environments. This enormous adaptive capacity depend on their ability to perceive cues from the micro-environment and process this information accordingly to mount appropriate metabolic responses and ultimately sustain homeostasis. From systems perspective, microbial cells conceal significant degree of organismal complexity, which may only be managed by continuous bulk cellular information flow and processing, inside the cell, between other cells and the environment. In this respect, reversible covalent modification of proteins is one of the universal mode of information flow mechanism used to regulate metabolism in all organisms. More than 30 types of post translational modifications have been identified, where phosphorylation constitutes nearly half of them. Bacterial cells possess several modes of phosphoprotein mediated information flow mechanisms. Histidine kinases and two component systems, bacterial tyrosine kinases, Hanks type serine/threonine kinases, atypical serine kinases and arginine kinases have been identified in many species.
Topics: Bacteria; Bacterial Proteins; Phosphorylation; Protein Kinases; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases
PubMed: 33539021
DOI: 10.1007/978-3-030-49844-3_12