Volume 5 (2021)
p38 regulates the tumor suppressor PDCD4 via the TSC-mTORC1 pathway
Clarissa Braun1,2, Karl Katholnig1, Christopher Kaltenecker3, Monika Linke1, Nyamdelger Sukhbaatar1, Markus Hengstschläger1 and Thomas Weichhart1
Programmed cell death protein 4 (PDCD4) exerts critical functions as tumor suppressor and in immune cells to regulate inflammatory processes. The phosphoinositide 3-kinase (PI3K) promotes degradation of PDCD4 via mammalian target of rapamycin complex 1 (mTORC1). However, additional pathways that may regulate PDCD4 expression are largely ill-defined. In this study, we have found that activation of the mitogen-activated protein kinase p38 promoted degradation of PDCD4 in macrophages and fibroblasts. Mechanistically, we identified a pathway from p38 and its substrate MAP kinase-activated protein kinase 2 (MK2) to the tuberous sclerosis complex (TSC) to regulate mTORC1-dependent (...)
Mechanisms of YAP/TAZ transcriptional control
Giusy Battilana1, Francesca Zanconato1 and Stefano Piccolo1,2
Dysregulated gene expression is intrinsic to cell transformation, tumorigenesis and metastasis. Cancer-specific gene-expression profiles stem from gene regulatory networks fueled by genetic and epigenetic defects, and by abnormal signals of the tumor microenvironment. These oncogenic signals ultimately engage the transcriptional machinery on the cis -regulatory elements of a host of effector genes, through recruitment of transcription factors (TFs), co-activators and chromatin regulators. That said, whether gene -expression in cancer cells is the chaotic product of myriad regulations or rather a relatively ordered process orchestrated by few TFs (master regulators) has long remained enigmatic. Recent work on the YAP/TAZ co-activators has been instrumental to break new ground into this outstanding issue, revealing that tumor cells hijack growth programs that are active during development and regeneration through engagement of a small set of interconnected TFs and their nuclear partners.
GRASPing the unconventional secretory machinery to bridge cellular stress signaling to the extracellular proteome
Constantinos Demetriades1,2, Julian Nüchel1 and Markus Plomann3
Part of the cellular response to stress is an evolutionarily conserved, poorly-understood process called unconventional protein secretion (UPS). Although cells shut down conventional/bulk secretion to save resources upon stress, UPS
Macroautophagy and normal aging of the nervous system: Lessons from animal models
Emmanouela Kallergi1 and Vassiliki Nikoletopoulou1
Aging represents a cumulative form of cellular stress, which is thought to challenge many aspects of proteostasis. The non-dividing, long-lived neurons are particularly vulnerable to stress, and, not surprisingly, even normal aging is highly associated with a decline in brain function in humans, as well as in other animals. Macroautophagy is a fundamental arm of the proteostasis network, safeguarding proper protein turnover during different cellular states and against diverse cellular stressors. An intricate interplay between macroautophagy and aging is beginning to unravel, with the emergence of new tools, including those for monitoring autophagy in cultured neurons and in the nervous system of different organisms in vivo. Here, we review recent findings on the impact of aging on neuronal integrity and on neuronal macroautophagy, as they emerge from studies in invertebrate and mammalian models.
Atg8ylation as a general membrane stress and remodeling response
Suresh Kumar1,2, Jingyue Jia1,2 and Vojo Deretic1,2
The yeast Atg8 protein and its paralogs in mammals, mammalian Atg8s (mAtg8s), have been primarily appreciated for their participation in autophagy. However, lipidated mAtg8s, including the most frequently used autophagosomal membrane marker LC3B, are found on cellular membranes other than autophagosomes. Here we put forward a hypothesis that the lipidation of mAtg8s, termed ‘Atg8ylation’, is a general membrane stress and remodeling response analogous to the role that ubiquitylation plays in tagging proteins. Ubiquitin and mAtg8s are related in sequence and structure, and the lipidation of mAtg8s occurs on its C-terminal glycine, akin to the C-terminal glycine of ubiquitin. Conceptually, we propose that mAtg8s and Atg8ylation are to membranes what ubiquitin and ubiquitylation are to proteins, and that, like ubiquitylation, Atg8ylation has a multitude of downstream effector outputs, one of which is autophagy.
PDLIM1: Structure, function and implication in cancer
Jian-Kang Zhou1, Xin Fan1, Jian Cheng1,2, Wenrong Liu1 and Yong Peng1
PDLIM1, a member of the PDZ-LIM family, is a cytoskeletal protein and functions as a platform to form distinct protein complexes, thus participating in multiple physiological processes such as cytoskeleton regulation and synapse formation. Emerging evidence demonstrates that PDLIM1 is dysregualted in a variety of tumors and plays essential roles in tumor initiation and progression. In this review, we summarize the structure and function of PDLIM1, as well as its important roles in human cancers.
Towards a better understanding of the neuro-developmental role of autophagy in sickness and in health
Juan Zapata-Muñoz1, Beatriz Villarejo-Zori1, Pablo Largo-Barrientos2 and Patricia Boya1
Autophagy is a critical cellular process by which biomolecules and cellular organelles are degraded in an orderly manner inside lysosomes. This process is particularly important in neurons: these post-mitotic cells cannot divide or be easily replaced and are therefore especially sensitive to the accumulation of toxic proteins and damaged organelles. Dysregulation of neuronal autophagy is well documented in a range of neurodegenerative diseases. However, growing evidence indicates that autophagy also critically contributes to neurodevelopmental cellular processes, including neurogenesis, maintenance of neural stem cell homeostasis, differentiation, metabolic reprogramming, and synaptic remodelling. These findings implicate autophagy in neurodevelopmental disorders. In this review we discuss the current understanding of the role of autophagy in neurodevelopment and neurodevelopmental disorders, as well as currently available tools and techniques that (...)
Innate RIG-I signaling restores antigen presentation in tumors and overcomes T cell resistance
Beatrice Thier1,2 and Annette Paschen1,2
In recent years, therapy with immune modulating antibodies, termed immune checkpoint blockade (ICB), has revolutionized the treatment of advanced metastatic melanoma, yielding long-lasting clinical responses in a subgroup of patients. But despite this remarkable progress, resistance to therapy represents a major clinical challenge. ICB efficacy is critically dependent on cytotoxic CD8+ T cells targeting tumor cells in an HLA class I (HLA-I) antigen-dependent manner. Transcriptional suppression of the HLA-I antigen processing and presentation machinery (HLA-I APM) in melanoma cells leads to HLA-I-low/-negative tumor cell phenotypes escaping CD8+ T cell recognition and contributing to ICB resistance. In general, HLA-I-low/-negative tumor cells can be re-sensitized to T cells by interferons (IFN), augmenting HLA-I APM expression. However, this mechanism fails when melanoma cells acquire resistance to IFN, which recently turned out as a key resistance mechanism in (...)
To promote or inhibit glioma progression, that is the question for IL-33
Stephen M. Robbins1 and Donna L. Senger1
Glioblastoma represents one of the most fatal of human cancers. Although there has been progress in the treatment of glioblastoma as a result of a treatment regimen that combines maximal
Mechanisms of YAP/TAZ transcriptional control
Giusy Battilana1, Francesca Zanconato1 and Stefano Piccolo1,2
Dysregulated gene expression is intrinsic to cell transformation, tumorigenesis and metastasis. Cancer-specific gene-expression profiles stem from gene regulatory networks fueled by genetic and epigenetic defects, and by abnormal signals of the tumor microenvironment. These oncogenic signals ultimately engage the transcriptional machinery on the cis -regulatory elements of a host of effector genes, through recruitment of transcription factors (TFs), co-activators and chromatin regulators. That said, whether gene -expression in cancer cells is the chaotic product of myriad regulations or rather a relatively ordered process orchestrated by few TFs (master regulators) has long remained enigmatic. Recent work on the YAP/TAZ co-activators has been instrumental to break new ground into this outstanding issue, revealing that tumor cells hijack growth programs that are active during development and regeneration through engagement of a small set of interconnected TFs and their nuclear partners.
GRASPing the unconventional secretory machinery to bridge cellular stress signaling to the extracellular proteome
Constantinos Demetriades1,2, Julian Nüchel1 and Markus Plomann3
Part of the cellular response to stress is an evolutionarily conserved, poorly-understood process called unconventional protein secretion (UPS). Although cells shut down conventional/bulk secretion to save resources upon stress, UPS
Macroautophagy and normal aging of the nervous system: Lessons from animal models
Emmanouela Kallergi1 and Vassiliki Nikoletopoulou1
Aging represents a cumulative form of cellular stress, which is thought to challenge many aspects of proteostasis. The non-dividing, long-lived neurons are particularly vulnerable to stress, and, not surprisingly, even normal aging is highly associated with a decline in brain function in humans, as well as in other animals. Macroautophagy is a fundamental arm of the proteostasis network, safeguarding proper protein turnover during different cellular states and against diverse cellular stressors. An intricate interplay between macroautophagy and aging is beginning to unravel, with the emergence of new tools, including those for monitoring autophagy in cultured neurons and in the nervous system of different organisms in vivo. Here, we review recent findings on the impact of aging on neuronal integrity and on neuronal macroautophagy, as they emerge from studies in invertebrate and mammalian models.
Atg8ylation as a general membrane stress and remodeling response
Suresh Kumar1,2, Jingyue Jia1,2 and Vojo Deretic1,2
The yeast Atg8 protein and its paralogs in mammals, mammalian Atg8s (mAtg8s), have been primarily appreciated for their participation in autophagy. However, lipidated mAtg8s, including the most frequently used autophagosomal membrane marker LC3B, are found on cellular membranes other than autophagosomes. Here we put forward a hypothesis that the lipidation of mAtg8s, termed ‘Atg8ylation’, is a general membrane stress and remodeling response analogous to the role that ubiquitylation plays in tagging proteins. Ubiquitin and mAtg8s are related in sequence and structure, and the lipidation of mAtg8s occurs on its C-terminal glycine, akin to the C-terminal glycine of ubiquitin. Conceptually, we propose that mAtg8s and Atg8ylation are to membranes what ubiquitin and ubiquitylation are to proteins, and that, like ubiquitylation, Atg8ylation has a multitude of downstream effector outputs, one of which is autophagy.
PDLIM1: Structure, function and implication in cancer
Jian-Kang Zhou1, Xin Fan1, Jian Cheng1,2, Wenrong Liu1 and Yong Peng1
PDLIM1, a member of the PDZ-LIM family, is a cytoskeletal protein and functions as a platform to form distinct protein complexes, thus participating in multiple physiological processes such as cytoskeleton regulation and synapse formation. Emerging evidence demonstrates that PDLIM1 is dysregualted in a variety of tumors and plays essential roles in tumor initiation and progression. In this review, we summarize the structure and function of PDLIM1, as well as its important roles in human cancers.
Towards a better understanding of the neuro-developmental role of autophagy in sickness and in health
Juan Zapata-Muñoz1, Beatriz Villarejo-Zori1, Pablo Largo-Barrientos2 and Patricia Boya1
Autophagy is a critical cellular process by which biomolecules and cellular organelles are degraded in an orderly manner inside lysosomes. This process is particularly important in neurons: these post-mitotic cells cannot divide or be easily replaced and are therefore especially sensitive to the accumulation of toxic proteins and damaged organelles. Dysregulation of neuronal autophagy is well documented in a range of neurodegenerative diseases. However, growing evidence indicates that autophagy also critically contributes to neurodevelopmental cellular processes, including neurogenesis, maintenance of neural stem cell homeostasis, differentiation, metabolic reprogramming, and synaptic remodelling. These findings implicate autophagy in neurodevelopmental disorders. In this review we discuss the current understanding of the role of autophagy in neurodevelopment and neurodevelopmental disorders, as well as currently available tools and techniques that (...)
Ribosome traffic jam in neurodegeneration: decoding hurdles in Huntington disease
Srinivasa Subramaniam1
The symptoms of HD, a neurodegenerative disorder, are severe disruption of cognitive and motor functions, including changes in posture and gait. HTT, the gene responsible for HD, is CAG (codes
The evolution of the concept of stress and the framework of the stress system
Siyu Lu1, Fang Wei1,2 and Guolin Li1,2,3
Stress is a central concept in biology and has now been widely used in psychological, physiological, social, and even environmental fields. However, the concept of stress was cross-utilized to refer to different elements of the stress system including stressful stimulus, stressor, stress response, and stress effect. Here, we summarized the evolution of the concept of stress and the framework of the stress system. We find although the concept of stress is developed from Selye’s “general adaptation syndrome”, it has now expanded and evolved significantly. Stress is now defined as a state of homeostasis being challenged, including both system stress and local stress. A specific stressor may potentially bring about specific local stress, while the intensity of stress beyond a threshold may commonly activate the hypothalamic-pituitary-adrenal axis and result in a systematic stress response. The framework of the stress system indicates that stress includes three types: (...)
Spermidine supplementation in rare translation-associated disorders
Andreas Zimmermann1,2, Didac Carmona-Gutierrez1, and Frank Madeo1,2,3
Spermidine is a naturally occurring polyamine that is strongly involved in manifold cellular processes, for example, DNA, RNA and protein stabilization, cell growth, proliferation, autophagy, and aging. Importantly, spermidine has