Marta Cruces-Sande, Arcones, Alba C, Vila-Bedmar, Rocío , Val-Blasco, Almudena , Sharabi, Kfir , Díaz-Rodríguez, Daniel , Puigserver, Pere , Mayor, Federico , and Murga, Cristina . 2020.
“Autophagy Mediates Hepatic Grk2 Degradation To Facilitate Glucagon-Induced Metabolic Adaptation To Fasting”. Faseb J, 34, 1, Pp. 399-409. doi:10.1096/fj.201901444R.
Abstract The liver plays a key role during fasting to maintain energy homeostasis and euglycemia via metabolic processes mainly orchestrated by the insulin/glucagon ratio. We report here that fasting or calorie restriction protocols in C57BL6 mice promote a marked decrease in the hepatic protein levels of G protein-coupled receptor kinase 2 (GRK2), an important negative modulator of both G protein-coupled receptors (GPCRs) and insulin signaling. Such downregulation of GRK2 levels is liver-specific and can be rapidly reversed by refeeding. We find that autophagy, and not the proteasome, represents the main mechanism implicated in fasting-induced GRK2 degradation in the liver in vivo. Reducing GRK2 levels in murine primary hepatocytes facilitates glucagon-induced glucose production and enhances the expression of the key gluconeogenic enzyme Pck1. Conversely, preventing full downregulation of hepatic GRK2 during fasting using adenovirus-driven overexpression of this kinase in the liver leads to glycogen accumulation, decreased glycemia, and hampered glucagon-induced gluconeogenesis, thus preventing a proper and complete adaptation to nutrient deprivation. Overall, our data indicate that physiological fasting-induced downregulation of GRK2 in the liver is key for allowing complete glucagon-mediated responses and efficient metabolic adaptation to fasting in vivo.
M. Cruces-Sande, Arcones, A. C. , Vila-Bedmar, R. , Val-Blasco, A. , Sharabi, K. , Diaz-Rodriguez, D. , Puigserver, P. , Mayor, F., Jr. , and Murga, C. . 2020.
“Autophagy Mediates Hepatic Grk2 Degradation To Facilitate Glucagon-Induced Metabolic Adaptation To Fasting”. Faseb J, 34, Pp. 399-409.
Abstract The liver plays a key role during fasting to maintain energy homeostasis and euglycemia via metabolic processes mainly orchestrated by the insulin/glucagon ratio. We report here that fasting or calorie restriction protocols in C57BL6 mice promote a marked decrease in the hepatic protein levels of G protein-coupled receptor kinase 2 (GRK2), an important negative modulator of both G protein-coupled receptors (GPCRs) and insulin signaling. Such downregulation of GRK2 levels is liver-specific and can be rapidly reversed by refeeding. We find that autophagy, and not the proteasome, represents the main mechanism implicated in fasting-induced GRK2 degradation in the liver in vivo. Reducing GRK2 levels in murine primary hepatocytes facilitates glucagon-induced glucose production and enhances the expression of the key gluconeogenic enzyme Pck1. Conversely, preventing full downregulation of hepatic GRK2 during fasting using adenovirus-driven overexpression of this kinase in the liver leads to glycogen accumulation, decreased glycemia, and hampered glucagon-induced gluconeogenesis, thus preventing a proper and complete adaptation to nutrient deprivation. Overall, our data indicate that physiological fasting-induced downregulation of GRK2 in the liver is key for allowing complete glucagon-mediated responses and efficient metabolic adaptation to fasting in vivo.
C. Luo, Liang, J. , Sharabi, K. , Hatting, M. , Perry, E. A. , Tavares, C. D. J. , Goyal, L. , Srivastava, A. , Bilodeau, M. , Zhu, A. X. , Sicinski, P. , and Puigserver, P. . 2020.
“Obesity/Type 2 Diabetes-Associated Liver Tumors Are Sensitive To Cyclin D1 Deficiency”. Cancer Res.
Abstract Type 2 diabetes, which is mainly linked to obesity, is associated with increased incidence of liver cancer. We have previously found that in various models of obesity/diabetes, hyperinsulinemia maintains heightened hepatic expression of cyclin D1, suggesting a plausible mechanism linking diabetes and liver cancer progression. Here we show that cyclin D1 is greatly elevated in human livers with diabetes and is among the most significantly upregulated genes in obese/diabetic liver tumors. Liver-specific cyclin D1 deficiency protected obese/diabetic mice against hepatic tumorigenesis, whereas lean/nondiabetic mice developed tumors irrespective of cyclin D1 status. Cyclin D1 dependency positively correlated with liver cancer sensitivity to palbociclib, an FDA-approved CDK4 inhibitor, which was effective in treating orthotopic liver tumors under obese/diabetic conditions. The antidiabetic drug metformin suppressed insulin-induced hepatic cyclin D1 expression and protected against obese/diabetic hepatocarcinogenesis. These results indicate that the cyclin D1-CDK4 complex represents a potential selective therapeutic vulnerability for liver tumors in obese/diabetic patients. SIGNIFICANCE: Obesity/diabetes-associated liver tumors are specifically vulnerable to cyclin D1 deficiency and CDK4 inhibition, suggesting that the obese/diabetic environment confers cancer-selective dependencies that can be therapeutically exploited.
Chi Luo, Liang, Jiaxin , Sharabi, Kfir , Hatting, Maximilian , Perry, Elizabeth A, Tavares, Clint DJ, Goyal, Lipika , Srivastava, Amitabh , Bilodeau, Marc , Zhu, Andrew X, Sicinski, Piotr , and Puigserver, Pere . 2020.
“Obesity/Type 2 Diabetes-Associated Liver Tumors Are Sensitive To Cyclin D1 Deficiency”. Cancer Res, 80, 16, Pp. 3215-3221. doi:10.1158/0008-5472.CAN-20-0106.
Abstract Type 2 diabetes, which is mainly linked to obesity, is associated with increased incidence of liver cancer. We have previously found that in various models of obesity/diabetes, hyperinsulinemia maintains heightened hepatic expression of cyclin D1, suggesting a plausible mechanism linking diabetes and liver cancer progression. Here we show that cyclin D1 is greatly elevated in human livers with diabetes and is among the most significantly upregulated genes in obese/diabetic liver tumors. Liver-specific cyclin D1 deficiency protected obese/diabetic mice against hepatic tumorigenesis, whereas lean/nondiabetic mice developed tumors irrespective of cyclin D1 status. Cyclin D1 dependency positively correlated with liver cancer sensitivity to palbociclib, an FDA-approved CDK4 inhibitor, which was effective in treating orthotopic liver tumors under obese/diabetic conditions. The antidiabetic drug metformin suppressed insulin-induced hepatic cyclin D1 expression and protected against obese/diabetic hepatocarcinogenesis. These results indicate that the cyclin D1-CDK4 complex represents a potential selective therapeutic vulnerability for liver tumors in obese/diabetic patients. SIGNIFICANCE: Obesity/diabetes-associated liver tumors are specifically vulnerable to cyclin D1 deficiency and CDK4 inhibition, suggesting that the obese/diabetic environment confers cancer-selective dependencies that can be therapeutically exploited.
C. D. J. Tavares, Aigner, S. , Sharabi, K. , Sathe, S. , Mutlu, B. , Yeo, G. W. , and Puigserver, P. . 2020.
“Transcriptome-Wide Analysis Of Pgc-1Alpha-Binding Rnas Identifies Genes Linked To Glucagon Metabolic Action”. Proc Natl Acad Sci U S A.
Abstract The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1alpha) is a transcriptional coactivator that controls expression of metabolic/energetic genes, programming cellular responses to nutrient and environmental adaptations such as fasting, cold, or exercise. Unlike other coactivators, PGC-1alpha contains protein domains involved in RNA regulation such as serine/arginine (SR) and RNA recognition motifs (RRMs). However, the RNA targets of PGC-1alpha and how they pertain to metabolism are unknown. To address this, we performed enhanced ultraviolet (UV) cross-linking and immunoprecipitation followed by sequencing (eCLIP-seq) in primary hepatocytes induced with glucagon. A large fraction of RNAs bound to PGC-1alpha were intronic sequences of genes involved in transcriptional, signaling, or metabolic function linked to glucagon and fasting responses, but were not the canonical direct transcriptional PGC-1alpha targets such as OXPHOS or gluconeogenic genes. Among the top-scoring RNA sequences bound to PGC-1alpha were Foxo1, Camk1delta, Per1, Klf15, Pln4, Cluh, Trpc5, Gfra1, and Slc25a25 PGC-1alpha depletion decreased a fraction of these glucagon-induced messenger RNA (mRNA) transcript levels. Importantly, knockdown of several of these genes affected glucagon-dependent glucose production, a PGC-1alpha-regulated metabolic pathway. These studies show that PGC-1alpha binds to intronic RNA sequences, some of them controlling transcript levels associated with glucagon action.
Clint DJ Tavares, Aigner, Stefan , Sharabi, Kfir , Sathe, Shashank , Mutlu, Beste , Yeo, Gene W, and Puigserver, Pere . 2020.
“Transcriptome-Wide Analysis Of Pgc-1Α-Binding Rnas Identifies Genes Linked To Glucagon Metabolic Action”. Proc Natl Acad Sci U S A, 117, 36, Pp. 22204-22213. doi:10.1073/pnas.2000643117.
Abstract The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a transcriptional coactivator that controls expression of metabolic/energetic genes, programming cellular responses to nutrient and environmental adaptations such as fasting, cold, or exercise. Unlike other coactivators, PGC-1α contains protein domains involved in RNA regulation such as serine/arginine (SR) and RNA recognition motifs (RRMs). However, the RNA targets of PGC-1α and how they pertain to metabolism are unknown. To address this, we performed enhanced ultraviolet (UV) cross-linking and immunoprecipitation followed by sequencing (eCLIP-seq) in primary hepatocytes induced with glucagon. A large fraction of RNAs bound to PGC-1α were intronic sequences of genes involved in transcriptional, signaling, or metabolic function linked to glucagon and fasting responses, but were not the canonical direct transcriptional PGC-1α targets such as OXPHOS or gluconeogenic genes. Among the top-scoring RNA sequences bound to PGC-1α were , δ, , , , , , , and PGC-1α depletion decreased a fraction of these glucagon-induced messenger RNA (mRNA) transcript levels. Importantly, knockdown of several of these genes affected glucagon-dependent glucose production, a PGC-1α-regulated metabolic pathway. These studies show that PGC-1α binds to intronic RNA sequences, some of them controlling transcript levels associated with glucagon action.