The awesome lysosome Ballabio, Andrea
EMBO molecular medicine,
February 2016, Volume:
8, Issue:
2
Journal Article
Peer reviewed
Open access
In the early 50s, Christian De Duve identified a new cellular structure, the lysosome, defined as the cell's “suicide bag” (de Duve, ). Sixty years later, it is clear that the lysosome greatly ...exceeded the expectations of its discoverer. Over 50 different types of lysosomal storage diseases have been identified, each due to the deficiency or malfunction of a specific lysosomal protein. In addition, an important role of the lysosome has been unveiled in several common human diseases, such as cancer, obesity, neurodegenerative diseases, and infection. Recent studies have led to the identification of a lysosome‐to‐nucleus signaling pathway and a lysosomal gene network that regulate cellular clearance and energy metabolism. These observations have opened a completely new field of research and changed our traditional view of the lysosome from a dead‐end organelle to a control center of cell metabolism. An important challenge for the future will be to exploit these discoveries to identify modulators of lysosomal function that may be used to treat human diseases.
The 2016 Louis‐Jeantet Prize for Medicine winner Andrea Ballabio offers an account of the current state of the art of lysosomal research in cell biology and disease.
Exciting new discoveries have transformed the view of the lysosome from a static organelle dedicated to the disposal and recycling of cellular waste to a highly dynamic structure that mediates the ...adaptation of cell metabolism to environmental cues. Lysosome-mediated signalling pathways and transcription programmes are able to sense the status of cellular metabolism and control the switch between anabolism and catabolism by regulating lysosomal biogenesis and autophagy. The lysosome also extensively communicates with other cellular structures by exchanging content and information and by establishing membrane contact sites. It is now clear that lysosome positioning is a dynamically regulated process and a crucial determinant of lysosomal function. Finally, growing evidence indicates that the role of lysosomal dysfunction in human diseases goes beyond rare inherited diseases, such as lysosomal storage disorders, to include common neurodegenerative and metabolic diseases, as well as cancer. Together, these discoveries highlight the lysosome as a regulatory hub for cellular and organismal homeostasis, and an attractive therapeutic target for a broad variety of disease conditions.
TFEB at a glance Napolitano, Gennaro; Ballabio, Andrea
Journal of cell science,
07/2016, Volume:
129, Issue:
13
Journal Article
Peer reviewed
Open access
The transcription factor EB (TFEB) plays a pivotal role in the regulation of basic cellular processes, such as lysosomal biogenesis and autophagy. The subcellular localization and activity of TFEB ...are regulated by mechanistic target of rapamycin (mTOR)-mediated phosphorylation, which occurs at the lysosomal surface. Phosphorylated TFEB is retained in the cytoplasm, whereas dephosphorylated TFEB translocates to the nucleus to induce the transcription of target genes. Thus, a lysosome-to-nucleus signaling pathway regulates cellular energy metabolism through TFEB. Recently, in vivo studies have revealed that TFEB is also involved in physiological processes, such as lipid catabolism. TFEB has attracted a lot of attention owing to its ability to induce the intracellular clearance of pathogenic factors in a variety of murine models of disease, such as Parkinson's and Alzheimer's, suggesting that novel therapeutic strategies could be based on the modulation of TFEB activity. In this Cell Science at a Glance article and accompanying poster, we present an overview of the latest research on TFEB function and its implication in human diseases.
Lysosomal storage diseases are a group of rare, inborn, metabolic errors characterized by deficiencies in normal lysosomal function and by intralysosomal accumulation of undegraded substrates. The ...past 25 years have been characterized by remarkable progress in the treatment of these diseases and by the development of multiple therapeutic approaches. These approaches include strategies aimed at increasing the residual activity of a missing enzyme (enzyme replacement therapy, hematopoietic stem cell transplantation, pharmacological chaperone therapy and gene therapy) and approaches based on reducing the flux of substrates to lysosomes. As knowledge has improved about the pathophysiology of lysosomal storage diseases, novel targets for therapy have been identified, and innovative treatment approaches are being developed.
The autophagy–lysosomal pathway (ALP) is involved in the degradation of long-lived proteins. Deficits in the ALP result in protein aggregation, the generation of toxic protein species, and ...accumulation of dysfunctional organelles, which are hallmarks of Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and prion disease. Decades of research have therefore focused on enhancing the ALP in neurodegenerative diseases. More recently, transcription factor EB (TFEB), a major regulator of autophagy and lysosomal biogenesis, has emerged as a leading factor in addressing disease pathology. We review the regulation of the ALP and TFEB and their impact on neurodegenerative diseases. We also offer our perspective on the complex role of autophagy and TFEB in disease pathogenesis and its therapeutic implications through the examination of prion disease.
Autophagy is a fundamental catabolic process that plays a central role in health and disease. An efficient autophagic process relies on the cooperation of two distinct types of organelles: the ...autophagosome and the lysosome. We have identified a gene network that regulates the biogenesis and function of both organelles. Our findings reveal an important role of transcription in the regulation of starvation-induced autophagy, and link lysosomal biogenesis to autophagy.
Lysosomal storage diseases are a group of metabolic disorders caused by deficiencies of several components of lysosomal function. Most commonly affected are lysosomal hydrolases, which are involved ...in the breakdown and recycling of a variety of complex molecules and cellular structures. The understanding of lysosomal biology has progressively improved over time. Lysosomes are no longer viewed as organelles exclusively involved in catabolic pathways, but rather as highly dynamic elements of the autophagic‐lysosomal pathway, involved in multiple cellular functions, including signaling, and able to adapt to environmental stimuli. This refined vision of lysosomes has substantially impacted on our understanding of the pathophysiology of lysosomal disorders. It is now clear that substrate accumulation triggers complex pathogenetic cascades that are responsible for disease pathology, such as aberrant vesicle trafficking, impairment of autophagy, dysregulation of signaling pathways, abnormalities of calcium homeostasis, and mitochondrial dysfunction. Novel technologies, in most cases based on high‐throughput approaches, have significantly contributed to the characterization of lysosomal biology or lysosomal dysfunction and have the potential to facilitate diagnostic processes, and to enable the identification of new therapeutic targets.
In the last decade, our understanding of lysosomal storage diseases immensely improved. The current article comprehensively reviews recent advances in lysosomal storage diseases research and therapy development.
In Parkinson's disease (PD) there is a selective degeneration of neuromelanin-containing neurons, especially substantia nigra dopaminergic neurons. In humans, neuromelanin accumulates with age, the ...latter being the main risk factor for PD. The contribution of neuromelanin to PD pathogenesis remains unknown because, unlike humans, common laboratory animals lack neuromelanin. Synthesis of peripheral melanins is mediated by tyrosinase, an enzyme also present at low levels in the brain. Here we report that overexpression of human tyrosinase in rat substantia nigra results in age-dependent production of human-like neuromelanin within nigral dopaminergic neurons, up to levels reached in elderly humans. In these animals, intracellular neuromelanin accumulation above a specific threshold is associated to an age-dependent PD phenotype, including hypokinesia, Lewy body-like formation and nigrostriatal neurodegeneration. Enhancing lysosomal proteostasis reduces intracellular neuromelanin and prevents neurodegeneration in tyrosinase-overexpressing animals. Our results suggest that intracellular neuromelanin levels may set the threshold for the initiation of PD.
Spin qubits are considered to be among the most promising candidates for building a quantum processor. Group IV hole spin qubits are particularly interesting owing to their ease of operation and ...compatibility with Si technology. In addition, Ge offers the option for monolithic superconductor–semiconductor integration. Here, we demonstrate a hole spin qubit operating at fields below 10 mT, the critical field of Al, by exploiting the large out-of-plane hole g-factors in planar Ge and by encoding the qubit into the singlet-triplet states of a double quantum dot. We observe electrically controlled g-factor difference-driven and exchange-driven rotations with tunable frequencies exceeding 100 MHz and dephasing times of 1 μs, which we extend beyond 150 μs using echo techniques. These results demonstrate that Ge hole singlet-triplet qubits are competing with state-of-the-art GaAs and Si singlet-triplet qubits. In addition, their rotation frequencies and coherence are comparable with those of Ge single spin qubits, but singlet-triplet qubits can be operated at much lower fields, emphasizing their potential for on-chip integration with superconducting technologies.A singlet-triplet spin qubit using holes in a Ge quantum well is demonstrated, and can be operated at low magnetic fields of a few millitesla.
Macroautophagy is a major intracellular degradation process recognized as playing a central role in cell survival and longevity. This multistep process is extensively regulated at several levels, ...including post-translationally through the action of conserved longevity factors such as the nutrient sensor TOR. More recently, transcriptional regulation of autophagy genes has emerged as an important mechanism for ensuring the somatic maintenance and homeostasis necessary for a long life span. Autophagy is increased in many long-lived model organisms and contributes significantly to their longevity. In turn, conserved transcription factors, particularly the helix-loop-helix transcription factor TFEB and the forkhead transcription factor FOXO, control the expression of many autophagy-related genes and are important for life-span extension. In this review, we discuss recent progress in understanding the contribution of these transcription factors to macroautophagy regulation in the context of aging. We also review current research on epigenetic changes, such as histone modification by the deacetylase SIRT1, that influence autophagy-related gene expression and additionally affect aging. Understanding the molecular regulation of macroautophagy in relation to aging may offer new avenues for the treatment of age-related diseases.
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