Carbohydrates and lipids provide the majority of substrates to fuel mitochondrial oxidative phosphorylation (OXPHOS). Metabolic inflexibility, defined as an impaired ability to switch between these fuels, is implicated in a number of metabolic diseases. Here we explore the mechanism by which physical inactivity promotes metabolic inflexibility in skeletal muscle. We developed a mouse model of sedentariness, small mouse cage (SMC) that, unlike other classic models of disuse in mice, faithfully recapitulated metabolic responses that occur in humans. Bioenergetic phenotyping of skeletal muscle mitochondria displayed metabolic inflexibility induced by physical inactivity, demonstrated by a reduction in pyruvate-stimulated respiration (JO2) in absence of a change in palmitate-stimulated JO2. Pyruvate resistance in these mitochondria was likely driven by a decrease in phosphatidylethanolamine (PE) abundance in the mitochondrial membrane. Reduction in mitochondrial PE by heterozygous deletion of phosphatidylserine decarboxylase (PSD) was sufficient to induce metabolic inflexibility measured at the whole-body level, as well as at the level of skeletal muscle mitochondria. Low mitochondrial PE in C2C12 myotubes was sufficient to increase glucose flux towards lactate. We further implicate that resistance to pyruvate metabolism is due to attenuated mitochondrial entry via mitochondrial pyruvate carrier (MPC). These findings suggest a mechanism by which mitochondrial PE directly regulates MPC activity to modulate metabolic flexibility in mice.
Piyarat Siripoksup, Guoshen Cao, Ahmad A. Cluntun, J. Alan Maschek, Quentinn Pearce, Marisa J. Lang, Mi-Young Jeong, Hiroaki Eshima, Patrick J. Ferrara, Precious C. Opurum, Ziad S. Mahmassani, Alek D. Peterlin, Shinya Watanabe, Maureen A. Walsh, Eric B. Taylor, James E. Cox, Micah J. Drummond, Jared Rutter, Katsuhiko Funai
Clear cell renal cell carcinoma (ccRCC) is characterized by dysregulated hypoxia signaling and a tumor microenvironment (TME) highly enriched in myeloid and lymphoid cells. Loss of the von Hippel Lindau (VHL) gene is a critical early event in ccRCC pathogenesis and promotes stabilization of HIF. Whether VHL loss in cancer cells affects immune cells in the TME remains unclear. Using Vhl WT and Vhl-KO in vivo murine kidney cancer Renca models, we found that Vhl-KO tumors were more infiltrated by immune cells. Tumor-associated macrophages (TAMs) from Vhl-deficient tumors demonstrated enhanced in vivo glucose consumption, phagocytosis, and inflammatory transcriptional signatures, whereas lymphocytes from Vhl-KO tumors showed reduced activation and a lower response to anti–programmed cell death 1 (anti–PD-1) therapy in vivo. The chemokine CX3CL1 was highly expressed in human ccRCC tumors and was associated with Vhl deficiency. Deletion of Cx3cl1 in cancer cells decreased myeloid cell infiltration associated with Vhl loss to provide a mechanism by which Vhl loss may have contributed to the altered immune landscape. Here, we identify cancer cell–specific genetic features that drove environmental reprogramming and shaped the tumor immune landscape, with therapeutic implications for the treatment of ccRCC.
Melissa M. Wolf, Matthew Z. Madden, Emily N. Arner, Jackie E. Bader, Xiang Ye, Logan Vlach, Megan L. Tigue, Madelyn D. Landis, Patrick B. Jonker, Zaid Hatem, KayLee K. Steiner, Dakim K. Gaines, Bradley I. Reinfeld, Emma S. Hathaway, Fuxue Xin, M. Noor Tantawy, Scott M. Haake, Eric Jonasch, Alexander Muir, Vivian L. Weiss, Kathryn E. Beckermann, W. Kimryn Rathmell, Jeffrey C. Rathmell
Lactylation has been recently identified as a new type of posttranslational modification widely occurring on lysine residues of both histone and non-histone proteins. The acetyl transferase p300 is thought to mediate protein lactylation, yet the cellular concentration of the proposed lactyl-donor, lactyl-coenzyme A is about 1,000 times lower than that of acetyl-CoA, raising the question whether p300 is a genuine lactyl-transferase. Here, we report the Alanyl-tRNA synthetase 1 (AARS1) moonlights as a bona fide lactyl-transferase that directly uses lactate and ATP to catalyze protein lactylation. Among the candidate substrates, we focused on the Hippo pathway that has a well-established role in tumorigenesis. Specifically, AARS1 was found to sense intracellular lactate and translocate into the nucleus to lactylate and activate YAP-TEAD complex; and AARS1 itself was identified as a Hippo target gene that forms a positive feedback loop with YAP-TEAD to promote gastric cancer (GC) cell proliferation. Consistently, the expression of AARS1 was found to be upregulated in GC, and elevated AARS1 expression was found to be associated with poor prognosis for GC patients. Collectively, this work discovered AARS1 with lactyl-transferase activity in vitro and in vivo and revealed how the metabolite lactate is translated into a signal of cell proliferation.
Junyi Ju, Hui Zhang, Moubin Lin, Zifeng Yan, Liwei An, Zhifa Cao, Dandan Geng, Jingwu Yue, Yang Tang, Luyang Tian, Fan Chen, Yi Han, Wenjia Wang, Shimin Zhao, Jiao Shi, Zhaocai Zhou
Gianfranco Di Giuseppe, Laura Soldovieri, Gea Ciccarelli, Pietro Manuel Ferraro, Giuseppe Quero, Francesca Cinti, Umberto Capece, Simona Moffa, Enrico Celestino Nista, Antonio Gasbarrini, Andrea Mari, Sergio Alfieri, Vincenzo Tondolo, Alfredo Pontecorvi, Jens Juul Holst, Andrea Giaccari, Teresa Mezza
Antitumor responses of CD8+ T cells are tightly regulated by distinct metabolic fitness. High levels of glutathione (GSH) are observed in the majority of tumors contributing to cancer progression and treatment resistance in part by preventing glutathione peroxidase 4 (GPX4) dependent ferroptosis. Here, we show the necessity of the adenosine A2A receptor (A2AR) signaling and the glutathione (GSH)-GPX4 axis in orchestrating metabolic fitness and survival of functionally competent CD8+ T cells. Activated CD8+ T cells treated ex vivo with simultaneous inhibition of A2AR and lipid peroxidation acquire a superior capacity to proliferate and persist in vivo, demonstrating a translatable means to prevent ferroptosis in adoptive cell therapy (ACT). Additionally, we identify a particular cluster of intratumoral CD8+ T cells expressing a putative gene signature of GSH metabolism (GMGS) in association with clinical response and survival across several human cancers. Our study addresses a key role of GSH-GPX4 and adenosinergic pathways in fine-tuning the metabolic fitness of antitumor CD8+ T cells.
Siqi Chen, Jie Fan, Ping Xie, Jihae Ahn, Michelle Fernandez, Leah K. Billingham, Jason Miska, Jennifer D. Wu, Derek A. Wainwright, Deyu Fang, Jeffrey A. Sosman, Yong Wan, Yi Zhang, Navdeep S. Chandel, Bin Zhang
In response to a meal, insulin drives hepatic glycogen synthesis to help regulate systemic glucose homeostasis. The mechanistic target of rapamycin complex 1 (mTORC1) is a well-established insulin target and contributes to the postprandial control of liver lipid metabolism, autophagy, and protein synthesis. However, its role in hepatic glucose metabolism is less understood. Here, we used metabolomics, isotope tracing, and mouse genetics to define a role for liver mTORC1 signaling in the control of postprandial glycolytic intermediates and glycogen deposition. We show that mTORC1 is required for glycogen synthase activity and glycogenesis. Mechanistically, hepatic mTORC1 activity promotes the feeding-dependent induction of Ppp1r3b, a gene encoding a phosphatase important for glycogen synthase activity whose polymorphisms are linked to human diabetes. Re-expression of Ppp1r3b in livers lacking mTORC1 signaling enhances glycogen synthase activity and restores postprandial glycogen content. mTORC1-dependent transcriptional control of Ppp1r3b is facilitated by FOXO1, a well characterized transcriptional regulator involved in the hepatic response to nutrient intake. Collectively, we identify a role for mTORC1 signaling in the transcriptional regulation of Ppp1r3b and the subsequent induction of postprandial hepatic glycogen synthesis.
Kahealani Uehara, Won Dong Lee, Megan Stefkovich, Dipsikha Biswas, Dominic Santoleri, Anna E. Garcia Whitlock, William J. Quinn III, Talia N. Coopersmith, Kate Townsend Creasy, Daniel J. Rader, Kei Sakamoto, Joshua D. Rabinowitz, Paul M. Titchenell
Wnts, cholesterol, and MAPK signaling are essential for development and adult homeostasis. Here we report for the first time that fatty acid hydroxylase domain containing 2 (FAXDC2), a previously uncharacterized enzyme, functions as a methyl sterol oxidase catalyzing C4 demethylation in the Kandutsch-Russell branch of the cholesterol biosynthesis pathway. FAXDC2, a paralog of MSMO1, regulates the abundance of specific C4-methyl sterols lophenol and dihydro-TMAS. Highlighting its clinical relevance, FAXDC2 is repressed in Wnt/β-catenin high cancer xenografts, in a mouse genetic model of Wnt activation, and in human colorectal cancers. Moreover, in primary human colorectal cancers, the sterol lophenol, regulated by FAXDC2, accumulates in the cancerous tissues and not in adjacent normal tissues. FAXDC2 links Wnts to RTK/MAPK signaling. Wnt inhibition drives increased recycling of RTKs and activation of the MAPK pathway, and this requires FAXDC2. Blocking Wnt signaling in Wnt-high cancers causes both differentiation and senescence; and this is prevented by knockout of FAXDC2. Our data shows the integration of three ancient pathways, Wnts, cholesterol synthesis, and RTK/MAPK signaling, in cellular proliferation and differentiation.
Babita Madan, Shawn R. Wadia, Siddhi Patnaik, Nathan Harmston, Emile K.W. Tan, Iain Bee Huat Tan, W. David Nes, Enrico Petretto, David M. Virshup
Aster proteins mediate the nonvesicular transport of cholesterol from the plasma membrane (PM) to the endoplasmic reticulum (ER). However, the importance of nonvesicular sterol movement for physiology and pathophysiology in various tissues is incompletely understood. Here we show that loss of Aster-B leads to diet-induced obesity and insulin resistance in female but not male mice, and that this sex difference is abolished by ovariectomy. We further demonstrate that Aster-B deficiency impairs nonvesicular cholesterol transport from the PM to the ER in ovaries in vivo, leading to hypogonadism and reduced estradiol synthesis. Female Aster-B-deficient mice exhibit reduced locomotor activity and energy expenditure, consistent with established effects of estrogens on systemic metabolism. Administration of exogenous estradiol ameliorates the diet-induced obesity phenotype of Aster-B-deficient female mice. These findings highlight the key role of Aster-B-dependent nonvesicular cholesterol transport in regulating estradiol production and protecting females from obesity.
Xu Xiao, John Paul Kennelly, An-Chieh Feng, Lijing Cheng, Beatriz Romartinez-Alonso, Alexander H. Bedard, Yajing Gao, Liujuan Cui, Stephen G. Young, John W.R. Schwabe, Peter Tontonoz
Melanocortin 4 receptor (MC4R) mutations are the most common cause of human monogenic obesity and are associated with hyperphagia and increased linear growth. While MC4R is known to activate Gsα/cAMP signaling, a significant proportion of obesity-associated MC4R mutations do not affect MC4R/Gsα signaling. To further explore the role of specific MC4R signaling pathways in regulation of energy balance, we examined the signaling properties of one such mutant MC4R (F51L), as well as the metabolic consequences of MC4RF51L mutation in mice. The MC4RF51L mutation produced a specific defect in MC4R/Gq/11α signaling and led to obesity, hyperphagia and increased linear growth in mice. The ability of a melanocortin agonist to acutely inhibit food intake when delivered to the paraventricular nucleus (PVN) was lost in MC4RF51L mice, as well as in wild-type mice in which a specific Gq/11α inhibitor was delivered to the PVN, providing evidence that a Gsα-independent signaling pathway, namely Gq/11α, significantly contributes to the actions of MC4R on food intake and linear growth. These results suggest that a biased MC4R agonist that primarily activates Gq/11α may be a potential agent to treat obesity with less untoward cardiovascular and other side effects.
Peter J. Metzger, Aileen Zhang, Bradley A. Carlson, Hui Sun, Zhenzhong Cui, Yongqi Li, Marshal T. Jahnke, Daniel R. Layton, Meenakshi B. Gupta, Naili Liu, Evi Kostenis, Oksana Gavrilova, Min Chen, Lee S. Weinstein
Manale El Kharbili, Sarah K. Sasse, Lynn Sanford, Sean Jacobson, Katja Aviszus, Arnav Gupta, Claire J. Guo, Susan M. Majka, Robin D. Dowell, Anthony N. Gerber, Russell P. Bowler, Fabienne Gally