bims-meprid 2023-10-29 papers

Issue of 2023‒10‒29
six papers selected by
Alessandro Carrer, Veneto Institute of Molecular Medicine

Nat Commun. 2023 Oct 23. 14(1): 6737

Metabolic regulation of proteome stability via N-terminal acetylation controls male germline stem cell differentiation and reproduction.

Charlotte M François, Thomas Pihl, Marion Dunoyer de Segonzac, Chloé Hérault, Bruno Hudry.

The molecular mechanisms connecting cellular metabolism with differentiation remain poorly understood. Here, we find that metabolic signals contribute to stem cell differentiation and germline homeostasis during Drosophila melanogaster spermatogenesis. We discovered that external citrate, originating outside the gonad, fuels the production of Acetyl-coenzyme A by germline ATP-citrate lyase (dACLY). We show that this pathway is essential during the final spermatogenic stages, where a high Acetyl-coenzyme A level promotes NatB-dependent N-terminal protein acetylation. Using genetic and biochemical experiments, we establish that N-terminal acetylation shields key target proteins, essential for spermatid differentiation, from proteasomal degradation by the ubiquitin ligase dUBR1. Our work uncovers crosstalk between metabolism and proteome stability that is mediated via protein post-translational modification. We propose that this system coordinates the metabolic state of the organism with gamete production. More broadly, modulation of proteome turnover by circulating metabolites may be a conserved regulatory mechanism to control cell functions.

DOI: https://doi.org/10.1038/s41467-023-42496-9

JCI Insight. 2023 Oct 23. pii: e165817. [Epub ahead of print]8(20):

Activation of acetyl-CoA synthetase 2 mediates kidney injury in diabetic nephropathy.

Jian Lu, Xue Qi Li, Pei Pei Chen, Jia Xiu Zhang, Liang Liu, Gui Hua Wang, Xiao Qi Liu, Ting Ting Jiang, Meng Ying Wang, Wen Tao Liu, Xiong Zhong Ruan, Kun Ling Ma.

Albuminuria and podocyte injury are the key cellular events in the progression of diabetic nephropathy (DN). Acetyl-CoA synthetase 2 (ACSS2) is a nucleocytosolic enzyme responsible for the regulation of metabolic homeostasis in mammalian cells. This study aimed to investigate the possible roles of ACSS2 in kidney injury in DN. We constructed an ACSS2-deleted mouse model to investigate the role of ACSS2 in podocyte dysfunction and kidney injury in diabetic mouse models. In vitro, podocytes were chosen and transfected with ACSS2 siRNA and ACSS2 inhibitor and treated with high glucose. We found that ACSS2 expression was significantly elevated in the podocytes of patients with DN and diabetic mice. ACSS2 upregulation promoted phenotype transformation and inflammatory cytokine expression while inhibiting podocytes' autophagy. Conversely, ACSS2 inhibition improved autophagy and alleviated podocyte injury. Furthermore, ACSS2 epigenetically activated raptor expression by histone H3K9 acetylation, promoting activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway. Pharmacological inhibition or genetic depletion of ACSS2 in the streptozotocin-induced diabetic mouse model greatly ameliorated kidney injury and podocyte dysfunction. To conclude, ACSS2 activation promoted podocyte injury in DN by raptor/mTORC1-mediated autophagy inhibition.

Keywords: Diabetes; Metabolism; Molecular biology; Nephrology

DOI: https://doi.org/10.1172/jci.insight.165817

Front Endocrinol (Lausanne). 2023 ;14 1274239

The connection between tricarboxylic acid cycle enzyme mutations and pseudohypoxic signaling in pheochromocytoma and paraganglioma.

Yuxiong Wang, Bin Liu, Faping Li, Yanghe Zhang, Xin Gao, Yishu Wang, Honglan Zhou.

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors originating from chromaffin cells, holding significant clinical importance due to their capacity for excessive catecholamine secretion and associated cardiovascular complications. Roughly 80% of cases are associated with genetic mutations. Based on the functionality of these mutated genes, PPGLs can be categorized into distinct molecular clusters: the pseudohypoxia signaling cluster (Cluster-1), the kinase signaling cluster (Cluster-2), and the WNT signaling cluster (Cluster-3). A pivotal factor in the pathogenesis of PPGLs is hypoxia-inducible factor-2α (HIF2α), which becomes upregulated even under normoxic conditions, activating downstream transcriptional processes associated with pseudohypoxia. This adaptation provides tumor cells with a growth advantage and enhances their ability to thrive in adverse microenvironments. Moreover, pseudohypoxia disrupts immune cell communication, leading to the development of an immunosuppressive tumor microenvironment. Within Cluster-1a, metabolic perturbations are particularly pronounced. Mutations in enzymes associated with the tricarboxylic acid (TCA) cycle, such as succinate dehydrogenase (SDHx), fumarate hydratase (FH), isocitrate dehydrogenase (IDH), and malate dehydrogenase type 2 (MDH2), result in the accumulation of critical oncogenic metabolic intermediates. Notable among these intermediates are succinate, fumarate, and 2-hydroxyglutarate (2-HG), which promote activation of the HIFs signaling pathway through various mechanisms, thus inducing pseudohypoxia and facilitating tumorigenesis. SDHx mutations are prevalent in PPGLs, disrupting mitochondrial function and causing succinate accumulation, which competitively inhibits α-ketoglutarate-dependent dioxygenases. Consequently, this leads to global hypermethylation, epigenetic changes, and activation of HIFs. In FH-deficient cells, fumarate accumulation leads to protein succination, impacting cell function. FH mutations also trigger metabolic reprogramming towards glycolysis and lactate synthesis. IDH1/2 mutations generate D-2HG, inhibiting α-ketoglutarate-dependent dioxygenases and stabilizing HIFs. Similarly, MDH2 mutations are associated with HIF stability and pseudohypoxic response. Understanding the intricate relationship between metabolic enzyme mutations in the TCA cycle and pseudohypoxic signaling is crucial for unraveling the pathogenesis of PPGLs and developing targeted therapies. This knowledge enhances our comprehension of the pivotal role of cellular metabolism in PPGLs and holds implications for potential therapeutic advancements.

Keywords: VHL/HIF axis; genetic mutations; metabolic reprogramming; paraganglioma; pheochromocytoma; pseudohypoxia; tricarboxylic acid cycle

DOI: https://doi.org/10.3389/fendo.2023.1274239

bioRxiv. 2023 Oct 10. pii: 2023.10.10.561739. [Epub ahead of print]

Lactoylglutathione promotes inflammatory signaling in macrophages.

Marissa N Trujillo, Erin Q Jennings, Emely A Hoffman, Hao Zhang, Aiden M Phoebe, Grace E Mastin, Naoya Kitamura, Julie A Reisz, Emily Megill, Daniel Kantner, Mariola M Marcinkiewicz, Shannon M Twardy, Felicidad Lebario, Eli Chapman, Rebecca L McCullough, Angelo D'Alessandro, Nathaniel W Snyder, Darren A Cusanovich, James J Galligan.

Chronic, systemic inflammation is a pathophysiological manifestation of metabolic disorders. Inflammatory signaling leads to elevated glycolytic flux and a metabolic shift towards aerobic glycolysis and lactate generation. This rise in lactate corresponds with increased generation of lactoylLys modifications on histones, mediating transcriptional responses to inflammatory stimuli. Lactoylation is also generated through a non-enzymatic S-to-N acyltransfer from the glyoxalase cycle intermediate, lactoylglutathione (LGSH). Here, we report a regulatory role for LGSH in inflammatory signaling. In the absence of the primary LGSH hydrolase, glyoxalase 2 (GLO2), RAW264.7 macrophages display significant elevations in LGSH, while demonstrating a potentiated inflammatory response when exposed to lipopolysaccharides, corresponding with a rise in histone lactoylation. Interestingly, our data demonstrate that lactoylation is associated with more compacted chromatin than acetylation in an unstimulated state, however, upon stimulation, regions of the genome associated with lactoylation become markedly more accessible. Lastly, we demonstrate a spontaneous S-to-S acyltransfer of lactate from LGSH to CoA, yielding lactoyl-CoA. This represents the first known mechanism for the generation of this metabolite. Collectively, these data suggest that LGSH, and not intracellular lactate, is a primary contributing factor facilitating the inflammatory response.

DOI: https://doi.org/10.1101/2023.10.10.561739

Nat Commun. 2023 Oct 27. 14(1): 6858

Mitochondrial dysfunction promotes the transition of precursor to terminally exhausted T cells through HIF-1α-mediated glycolytic reprogramming.

Hao Wu, Xiufeng Zhao, Sophia M Hochrein, Miriam Eckstein, Gabriela F Gubert, Konrad Knöpper, Ana Maria Mansilla, Arman Öner, Remi Doucet-Ladevèze, Werner Schmitz, Bart Ghesquière, Sebastian Theurich, Jan Dudek, Georg Gasteiger, Alma Zernecke, Sebastian Kobold, Wolfgang Kastenmüller, Martin Vaeth.

T cell exhaustion is a hallmark of cancer and persistent infections, marked by inhibitory receptor upregulation, diminished cytokine secretion, and impaired cytolytic activity. Terminally exhausted T cells are steadily replenished by a precursor population (Tpex), but the metabolic principles governing Tpex maintenance and the regulatory circuits that control their exhaustion remain incompletely understood. Using a combination of gene-deficient mice, single-cell transcriptomics, and metabolomic analyses, we show that mitochondrial insufficiency is a cell-intrinsic trigger that initiates the functional exhaustion of T cells. At the molecular level, we find that mitochondrial dysfunction causes redox stress, which inhibits the proteasomal degradation of hypoxia-inducible factor 1α (HIF-1α) and promotes the transcriptional and metabolic reprogramming of Tpex cells into terminally exhausted T cells. Our findings also bear clinical significance, as metabolic engineering of chimeric antigen receptor (CAR) T cells is a promising strategy to enhance the stemness and functionality of Tpex cells for cancer immunotherapy.

DOI: https://doi.org/10.1038/s41467-023-42634-3

Redox Biol. 2023 Oct 17. pii: S2213-2317(23)00333-6. [Epub ahead of print]67 102932

Defective function of α-ketoglutarate dehydrogenase exacerbates mitochondrial ATP deficits during complex I deficiency.

Gerardo G Piroli, Allison M Manuel, Richard S McCain, Holland H Smith, Oliver Ozohanics, Sara Mellid, J Hunter Cox, William E Cotham, Michael D Walla, Alberto Cascón, Attila Ambrus, Norma Frizzell.

The NDUFS4 knockout (KO) mouse phenotype resembles the human Complex I deficiency Leigh Syndrome. The irreversible succination of protein thiols by fumarate is increased in select regions of the NDUFS4 KO brain affected by neurodegeneration. We report that dihydrolipoyllysine-residue succinyltransferase (DLST), a component of the α-ketoglutarate dehydrogenase complex (KGDHC) of the tricarboxylic acid (TCA) cycle, is succinated in the affected regions of the NDUFS4 KO brain. Succination of DLST reduced KGDHC activity in the brainstem (BS) and olfactory bulb (OB) of KO mice. The defective production of KGDHC derived succinyl-CoA resulted in decreased mitochondrial substrate level phosphorylation (SLP), further aggravating the existing oxidative phosphorylation (OXPHOS) ATP deficit. Protein succinylation, an acylation modification that requires succinyl-CoA, was reduced in the KO mice. Modeling succination of a cysteine in the spatial vicinity of the DLST active site or introduction of succinomimetic mutations recapitulates these metabolic deficits. Our data demonstrate that the biochemical deficit extends beyond impaired Complex I assembly and OXPHOS deficiency, functionally impairing select components of the TCA cycle to drive metabolic perturbations in affected neurons.

Keywords: Alpha-ketoglutarate dehydrogenase; Complex I; Fumarate; Leigh syndrome; Protein succination; Substrate level phosphorylation

DOI: https://doi.org/10.1016/j.redox.2023.102932