Induction of oxidative metabolism by the p38α/MK2 pathway

Adequate responses to environmental stresses are essential for cell survival. The regulation of cellular energetics that involves mitochondrial energy production and oxidative stress is central in the process of stress adaptation and response. The p38α signalling pathway plays a key role in the response to stress stimuli by orchestrating multiple cellular processes. However, prolonged activation of the p38α pathway results in impaired cell proliferation and can lead to cell death. Here we use a system to specifically activate p38α signalling and show that sustained activation of this pathway suffices to induce important metabolic changes, including high dependence on glucose for cell survival, increased consumption of glutamine, enhanced respiration rate and elevated production of mitochondrial reactive oxygen species (ROS). Moreover, we provide evidence that increased production of mitochondrial superoxide as a consequence of elevated mitochondria activity, contributes to the p38α reduced cell survival triggered by sustained p38α activation. We also show that the p38α-activated kinase MAPKAPK2 (MK2) plays an important role orchestrating the observed metabolic changes. Our results illustrate a new function of p38α signalling in the regulation of cellular metabolism, which may lead to cell death upon persistent activation of the pathway

Overcoming Paradoxical Kinase Priming by a Novel MNK1 Inhibitor

Inhibidor de MNK1; OncologíaInhibidor de MNK1; OncologiaMNK1 inhibitor; OncologyTargeting the kinases MNK1 and MNK2 has emerged as a valuable strategy in oncology. However, most of the advanced inhibitors are acting in an adenosine triphosphate (ATP)-competitive mode, precluding the evaluation of different binding modes in preclinical settings. Using rational design, we identified and validated the 4,6-diaryl-pyrazolo[3,4-b]pyridin-3-amine scaffold as the core for MNK inhibitors. Signaling pathway analysis confirmed a direct effect of the hit compound EB1 on MNKs, and in line with the reported function of these kinases, EB1 only affects the growth of tumor but not normal cells. Molecular modeling revealed the binding of EB1 to the inactive conformation of MNK1 and the interaction with the specific DFD motif. This novel mode of action appears to be superior to the ATP-competitive inhibitors, which render the protein in a pseudo-active state. Overcoming this paradoxical activation of MNKs by EB1 represents therefore a promising starting point for the development of a novel generation of MNK inhibitors.This work was supported by the Instituto de Salud Carlos III (PI17/02247), (PI20/01687), and CIBERONC (CB16/12/00363). S.R.y.C. acknowledges support from the Generalitat de Catalunya (2017-9015-385045). E. Bou-Petit thanks the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2017 FI_B2 00139) and the European Social Funds for her predoctoral fellowship

Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death‐receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor‐induced apoptosis. TP53INP2 binds caspase‐8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase‐8 by TRAF6. We have defined a TRAF6‐interacting motif (TIM) and a ubiquitin‐interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase‐8 to TRAF6 for further polyubiquitination of caspase‐8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase‐8, and subsequently reduce levels of death receptor‐induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL‐induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase‐8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway

Regulation of Mammary Luminal Cell Fate and Tumorigenesis by p38α

Summary: Mammary stem and progenitor cells are essential for mammary gland homeostasis and are also candidates for cells of origin of mammary tumors. Here, we have investigated the function of the protein kinase p38α in the mammary gland using mice that delete this protein in the luminal epithelial cells. We show that p38α regulates the fate of luminal progenitor cells through modulation of the transcription factor RUNX1, an important controller of the estrogen receptor-positive cell lineage. We also provide evidence that the regulation of RUNX1 by p38α probably involves the kinase MSK1, which phosphorylates histone H3 at the RUNX1 promoter. Moreover, using a mouse model for breast cancer initiated by luminal cells, we show that p38α downregulation in mammary epithelial cells reduces tumor burden, which correlates with decreased numbers of tumor-initiating cells. Collectively, our results define a key role for p38α in luminal progenitor cell fate that affects mammary tumor formation

Induction of oxidative metabolism by the p38α/MK2 pathway

Adequate responses to environmental stresses are essential for cell survival. The regulation of cellular energetics that involves mitochondrial energy production and oxidative stress is central in the process of stress adaptation and response. The p38α signalling pathway plays a key role in the response to stress stimuli by orchestrating multiple cellular processes. However, prolonged activation of the p38α pathway results in impaired cell proliferation and can lead to cell death. Here we use a system to specifically activate p38α signalling and show that sustained activation of this pathway suffices to induce important metabolic changes, including high dependence on glucose for cell survival, increased consumption of glutamine, enhanced respiration rate and elevated production of mitochondrial reactive oxygen species (ROS). Moreover, we provide evidence that increased production of mitochondrial superoxide as a consequence of elevated mitochondria activity, contributes to the p38α reduced cell survival triggered by sustained p38α activation. We also show that the p38α-activated kinase MAPKAPK2 (MK2) plays an important role orchestrating the observed metabolic changes. Our results illustrate a new function of p38α signalling in the regulation of cellular metabolism, which may lead to cell death upon persistent activation of the pathway

Induction of oxidative metabolism by the p38α/MK2 pathway

Adequate responses to environmental stresses are essential for cell survival. The regulation of cellular energetics that involves mitochondrial energy production and oxidative stress is central in the process of stress adaptation and response. The p38α signalling pathway plays a key role in the response to stress stimuli by orchestrating multiple cellular processes. However, prolonged activation of the p38α pathway results in impaired cell proliferation and can lead to cell death. Here we use a system to specifically activate p38α signalling and show that sustained activation of this pathway suffices to induce important metabolic changes, including high dependence on glucose for cell survival, increased consumption of glutamine, enhanced respiration rate and elevated production of mitochondrial reactive oxygen species (ROS). Moreover, we provide evidence that increased production of mitochondrial superoxide as a consequence of elevated mitochondria activity, contributes to the p38α reduced cell survival triggered by sustained p38α activation. We also show that the p38α-activated kinase MAPKAPK2 (MK2) plays an important role orchestrating the observed metabolic changes. Our results illustrate a new function of p38α signalling in the regulation of cellular metabolism, which may lead to cell death upon persistent activation of the pathway

Induction of oxidative metabolism by the p38α/MK2 pathway

Adequate responses to environmental stresses are essential for cell survival. The regulation of cellular energetics that involves mitochondrial energy production and oxidative stress is central in the process of stress adaptation and response. The p38α signalling pathway plays a key role in the response to stress stimuli by orchestrating multiple cellular processes. However, prolonged activation of the p38α pathway results in impaired cell proliferation and can lead to cell death. Here we use a system to specifically activate p38α signalling and show that sustained activation of this pathway suffices to induce important metabolic changes, including high dependence on glucose for cell survival, increased consumption of glutamine, enhanced respiration rate and elevated production of mitochondrial reactive oxygen species (ROS). Moreover, we provide evidence that increased production of mitochondrial superoxide as a consequence of elevated mitochondria activity, contributes to the p38α reduced cell survival triggered by sustained p38α activation. We also show that the p38α-activated kinase MAPKAPK2 (MK2) plays an important role orchestrating the observed metabolic changes. Our results illustrate a new function of p38α signalling in the regulation of cellular metabolism, which may lead to cell death upon persistent activation of the pathway

Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death‐receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor‐induced apoptosis. TP53INP2 binds caspase‐8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase‐8 by TRAF6. We have defined a TRAF6‐interacting motif (TIM) and a ubiquitin‐interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase‐8 to TRAF6 for further polyubiquitination of caspase‐8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase‐8, and subsequently reduce levels of death receptor‐induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL‐induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase‐8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway

Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death‐receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor‐induced apoptosis. TP53INP2 binds caspase‐8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase‐8 by TRAF6. We have defined a TRAF6‐interacting motif (TIM) and a ubiquitin‐interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase‐8 to TRAF6 for further polyubiquitination of caspase‐8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase‐8, and subsequently reduce levels of death receptor‐induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL‐induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase‐8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway