The lysosome: from waste bag to potential therapeutic target
TL;DR: This review focuses on lysosomal involvement in digestion of intra- and extracellular material, plasma membrane repair, cholesterol homeostasis, and cell death.
Abstract: Lysosomes are ubiquitous membrane-bound intracellular organelles with an acidic interior. They are central for degradation and recycling of macromolecules delivered by endocytosis, phagocytosis, and autophagy. In contrast to the rather simplified view of lysosomes as waste bags, nowadays lysosomes are recognized as advanced organelles involved in many cellular processes and are considered crucial regulators of cell homeostasis. The function of lysosomes is critically dependent on soluble lysosomal hydrolases (e.g. cathepsins) as well as lysosomal membrane proteins (e.g. lysosome-associated membrane proteins). This review focuses on lysosomal involvement in digestion of intra- and extracellular material, plasma membrane repair, cholesterol homeostasis, and cell death. Regulation of lysosomal biogenesis and function via the transcription factor EB (TFEB) will also be discussed. In addition, lysosomal contribution to diseases, including lysosomal storage disorders, neurodegenerative disorders, cancer, and cardiovascular diseases, is presented.
Citations
More filters
TL;DR: A review of the biophysical properties and physiological functions of extracellular vesicles, particularly their pro-metastatic effects, and highlight the utility of EVs for the development of cancer diagnostics and therapeutics can be found in this paper.
Abstract: The sustained growth, invasion, and metastasis of cancer cells depend upon bidirectional cell-cell communication within complex tissue environments. Such communication predominantly involves the secretion of soluble factors by cancer cells and/or stromal cells within the tumour microenvironment (TME), although these cell types have also been shown to export membrane-encapsulated particles containing regulatory molecules that contribute to cell-cell communication. These particles are known as extracellular vesicles (EVs) and include species of exosomes and shed microvesicles. EVs carry molecules such as oncoproteins and oncopeptides, RNA species (for example, microRNAs, mRNAs, and long non-coding RNAs), lipids, and DNA fragments from donor to recipient cells, initiating profound phenotypic changes in the TME. Emerging evidence suggests that EVs have crucial roles in cancer development, including pre-metastatic niche formation and metastasis. Cancer cells are now recognized to secrete more EVs than their nonmalignant counterparts, and these particles can be isolated from bodily fluids. Thus, EVs have strong potential as blood-based or urine-based biomarkers for the diagnosis, prognostication, and surveillance of cancer. In this Review, we discuss the biophysical properties and physiological functions of EVs, particularly their pro-metastatic effects, and highlight the utility of EVs for the development of cancer diagnostics and therapeutics.
925 citations
TL;DR: The mechanism of macrophage polarization from the tumor microenvironment, nanocarriers, nuclear receptor PPARγ, phagocytosis, NF-κB signaling pathways, and other pathways is analyzed.
607 citations
TL;DR: The modulation of lysosome function could be a promising therapeutic strategy for the treatment of cancer as well as metabolic and neurodegenerative disorders.
Abstract: 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.
602 citations
TL;DR: The crosstalk between ER stress and autophagy and their signaling networks mainly in mammalian-based systems is summarized and current knowledge on selective autophagic and its connection to ER stress is highlighted.
Abstract: An accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) leads to stress conditions. To mitigate such circumstances, stressed cells activate a homeostatic intracellular signaling network cumulatively called the unfolded protein response (UPR), which orchestrates the recuperation of ER function. Macroautophagy (hereafter autophagy), an intracellular lysosome-mediated bulk degradation pathway for recycling and eliminating wornout proteins, protein aggregates, and damaged organelles, has also emerged as an essential protective mechanism during ER stress. These 2 systems are dynamically interconnected, and recent investigations have revealed that ER stress can either stimulate or inhibit autophagy. However, the stress-associated molecular cues that control the changeover switch between induction and inhibition of autophagy are largely obscure. This review summarizes the crosstalk between ER stress and autophagy and their signaling networks mainly in mammalian-based systems. Additionally, we highlight current knowledge on selective autophagy and its connection to ER stress.
545 citations
TL;DR: The endosomal-lysosomal system is emerging as a central player in a host of neurodegenerative diseases, demonstrating potential roles which are likely to be revealed in pathogenesis and for viable therapeutic strategies.
Abstract: The endosomal-lysosomal system is made up of a set of intracellular membranous compartments that dynamically interconvert, which is comprised of early endosomes, recycling endosomes, late endosomes, and the lysosome. In addition, autophagosomes execute autophagy, which delivers intracellular contents to the lysosome. Maturation of endosomes and/or autophagosomes into a lysosome creates an unique acidic environment within the cell for proteolysis and recycling of unneeded cellular components into usable amino acids and other biomolecular building blocks. In the endocytic pathway, gradual maturation of endosomes into a lysosome and acidification of the late endosome are accompanied by vesicle trafficking, protein sorting and targeted degradation of some sorted cargo. Two opposing sorting systems are operating in these processes: the endosomal sorting complex required for transport (ESCRT) supports targeted degradation and the retromer supports retrograde retrieval of certain cargo. The endosomal-lysosomal system is emerging as a central player in a host of neurodegenerative diseases, demonstrating potential roles which are likely to be revealed in pathogenesis and for viable therapeutic strategies. Here we focus on the physiological process of endosomal-lysosomal maturation, acidification and sorting systems along the endocytic pathway, and further discuss relationships between abnormalities in the endosomal-lysosomal system and neurodegenerative diseases, especially Alzheimer’s disease (AD).
387 citations
Cites background from "The lysosome: from waste bag to pot..."
...We have recently performed a systematic look at the proteomic effects of defective endosomal-lysosomal pH in a cellular model, in order to develop a better understanding of the global changes in the proteome that follow inhibition of V-ATPase and could be considered together as a signature or biomarker of defective vacuolar acidification [57, 58], which would be expected to have an overlap with changes seen in AD and/or other conditions which may be subject to this often agedependent defect....
[...]
References
More filters
TL;DR: This Review summarizes recent advances in understanding the physiological functions of autophagy and its possible roles in the causation and prevention of human diseases.
6,301 citations
"The lysosome: from waste bag to pot..." refers background in this paper
...Due to the essential role of lysosomes in autophagy, lysosomal dysfunction impairs this process, thereby contributing to disease (Levine and Kroemer, 2008)....
[...]
...Due to the essential role of lysosomes in autophagy, lysosomal dysfunction impairs this process, thereby contributing to disease (Levine and Kroemer, 2008)....
[...]
TL;DR: The approach was to apply the techniques of cell culture to unravel the postulated regulatory defect in FH, which led to the discovery of a cell surface receptor for a plasma cholesterol transport protein called low density lipoprotein (LDL) and to the elucidation of the mechanism by which this receptor mediates feedback control of cholesterol synthesis.
Abstract: In 1901 a physician, Archibald Garrod, observed a patient with black urine. He used this simple observation to demonstrate that a single mutant gene can produce a discrete block in a biochemical pathway, which he called an “inborn error of metabolism”. Garrod’s brilliant insight anticipated by 40 years the one gene-one enzyme concept of Beadle and Tatum. In similar fashion the chemist Linus Pauling and the biochemist Vernon Ingram, through study of patients with sickle cell anemia, showed that mutant genes alter the amino acid sequences of proteins. Clearly, many fundamental advances in biology were spawned by perceptive studies of human genetic diseases (1). We began our work in 1972 in an attempt to understand a human genetic disease, familial hypercholesterolemia or FH. In these patients the concentration of cholesterol in blood is elevated many fold above normal and heart attacks occur early in life. We postulated that this dominantly inherited disease results from a failure of end-product repression of cholesterol synthesis. The possibility fascinated us because genetic defects in feedback regulation had not been observed previously in humans or animals, and we hoped that study of this disease might throw light on fundamental regulatory mechanisms. Our approach was to apply the techniques of cell culture to unravel the postulated regulatory defect in FH. These studies led to the discovery of a cell surface receptor for a plasma cholesterol transport protein called low density lipoprotein (LDL) and to the elucidation of the mechanism by which this receptor mediates feedback control of cholesterol synthesis (2,3). FH was shown to be caused by inherited defects in the gene encoding the LDL receptor, which disrupt the normal control of cholesterol metabolism. Study of the LDL receptor in turn led to the understanding of receptor-mediated endocytosis, a genera! process by which cells communicate with each other through internalization of regulatory and nutritional molecules (4). Receptor-mediated endocytosis differs from previously described biochemical pathways because it depends upon the continuous and highly controlled movement of membraneembedded proteins from one cell organelle to another in a process termed
5,488 citations
"The lysosome: from waste bag to pot..." refers background in this paper
...In addition to de novo cholesterol synthesis in the ER, the uptake of low-density lipoprotein (LDL) via receptor-mediated endocytosis is an important route for cholesterol entry into the cell (Brown and Goldstein, 1986)....
[...]
TL;DR: It is explored how recent mouse models in combination with advances in human genetics are providing key insights into how the impairment or activation of autophagy contributes to pathogenesis of diverse diseases, from neurodegenerative diseases such as Parkinson disease to inflammatory disorders such as Crohn disease.
4,529 citations
"The lysosome: from waste bag to pot..." refers background in this paper
...There is normally a basal rate of autophagy in cells to maintain homeostasis, but it can be strongly induced to protect cells under various physiological stresses, such as nutrient depletion and the presence of aggregated proteins (Mizushima and Komatsu, 2011)....
[...]
...This secures the supply of building blocks in the cell during starvation and permits the disposal of unneeded or non-functional organelles (Mizushima and Komatsu, 2011)....
[...]
TL;DR: In this review particular emphasis is placed on the discrepancy between the concentrations ofadenosine, ADP, and ATP in the purine receptors of UDP and UTP.
Abstract: ### A. Overview
Extracellular purines (adenosine, ADP, and ATP) and pyrimidines (UDP and UTP) are important signaling molecules that mediate diverse biological effects via cell-surface receptors termed purine receptors. In this review particular emphasis is placed on the discrepancy between the
4,177 citations
"The lysosome: from waste bag to pot..." refers background in this paper
...Such extracellular ATP participates in communication that is mediated by a range of different ATP binding receptors (Ralevic and Burnstock, 1998)....
[...]
TL;DR: The results suggest that the continuous clearance of diffuse cytosolic proteins through basal autophagy is important for preventing the accumulation of abnormal proteins, which can disrupt neural function and ultimately lead to neurodegeneration.
Abstract: Autophagy is an intracellular bulk degradation process through which a portion of the cytoplasm is delivered to lysosomes to be degraded. Although the primary role of autophagy in many organisms is in adaptation to starvation, autophagy is also thought to be important for normal turnover of cytoplasmic contents, particularly in quiescent cells such as neurons. Autophagy may have a protective role against the development of a number of neurodegenerative diseases. Here we report that loss of autophagy causes neurodegeneration even in the absence of any disease-associated mutant proteins. Mice deficient for Atg5 (autophagy-related 5) specifically in neural cells develop progressive deficits in motor function that are accompanied by the accumulation of cytoplasmic inclusion bodies in neurons. In Atg5-/- cells, diffuse, abnormal intracellular proteins accumulate, and then form aggregates and inclusions. These results suggest that the continuous clearance of diffuse cytosolic proteins through basal autophagy is important for preventing the accumulation of abnormal proteins, which can disrupt neural function and ultimately lead to neurodegeneration.
3,684 citations
"The lysosome: from waste bag to pot..." refers background in this paper
...Correct autophagic function is essential for cells, particularly for neurons, which rely on autophagy for survival, and the inactivation of crucial autophagy genes in mice results in severe neurodegeneration (Hara et al., 2006; Komatsu et al., 2006)....
[...]