Autophagy

From Wikipedia, the free encyclopedia - View original article

 
Jump to: navigation, search
(A) Diagram of autophagy; (B) Electron micrograph of autophagic structures in the fatbody of a fruit fly larva; (C) Fluorescently labeled autophagosomes in liver cells of starved mice.

Autophagy (or autophagocytosis) (from the Greek words, auto "self" and phagein "to eat"), is the basic catabolic mechanism that involves cell degradation of unnecessary or dysfunctional cellular components through the actions of lysosomes.[1] The breakdown of cellular components can ensure cellular survival during starvation by maintaining cellular energy levels.[1] Autophagy, if regulated, ensures the synthesis, degradation and recycling of cellular components.[1] During this process, targeted cytoplasmic constituents are isolated from the rest of the cell within the autophagosome, which are then fused with lysosomes and degraded or recycled.[2] There are three different forms of autophagy that are commonly described; macroautophagy, microautophagy and chaperone-mediated autophagy.[3] In the context of disease, autophagy has been seen as an adaptive response to survival, whereas in other cases it appears to promote cell death and morbidity.[2]

The name "autophagy" was coined by Belgian biochemist Christian de Duve in 1963.[4]

Discovery and origin of the name[edit]

The process of autophagy was first observed by Keith R. Porter and his postdoctoral student Thomas Ashford at the Rockefeller Institute. In January 1962 they reported that there were an increased number of lysosomes in the liver cells of rat after addition of glucagon, and that some displaced lysosomes towards the centre of the cell contained other cell organelles such as mitochondria. This was the first evidence of intracellular digestion of cell organelles (which they called autolysis after Christian de Duve). However Porter and Ashford wrongly interpreted their data that the structures were lysosomes being formed (ignoring the pre-existing organelles), lysosomes could not be cell organelles but part of cytoplasm such as mitochondria, and that hydrolytic enzymes were produced by microbodies (now called peroxisomes, which do not have any digestive function).[5] Inspired by this discovery, the term "autophagy" was invented by de Duve, the Nobel Prize-winning discoverer of lysosomes and peroxisomes. Unlike Porter and Ashford, de Duve conceived the term as a part of lysosomal function while describing the role of glucagon as a major inducer of cell degradation in the liver. With his postdoctoral student Russell L. Peter, he subsequently established that lysosomes are indeed responsible for glucagon-induced autophagy.[6][7] This was the first time the fact that lysosomes are the sites of intracellular autophagy was established. He first publicly used the word at the first international symposium on lysosomes, the Ciba Foundation Symposium on Lysosomes held in London during 12–14 February 1963. He specifically introduced it while making a speech on "The Lysosome Concept" to explain the term "cytolysomes" introduced by Alex B. Novikoff.[4][8][9]

Process and Pathways[edit]

There are three main pathways involved in autophagy and these are mediated by the autophagy-related genes and their associated enzymes.[10][11]

Macroautophagy is the main pathway, occurring mainly to eradicate damaged cell organelles or unused proteins.[12] This involves the formation of a double membrane around cytoplasmic substrates resulting in the organelle known as an autophagosome.[11][13] In the canonical starvation-induced pathway, autophagosome formation is induced by class 3 phosphoinositide-3-kinase, the autophagy-related gene (Atg) 6 (also known as Beclin-1) and ubiquitin-like conjugation reactions.[14] Non-canonical PI3K/beclin 1-independent induction pathways have been described for injury-induced autophagy and mitophagy.[15] Both canonical and non-canonical pathways converge on the covalent conjugation of Atg8 homologues to phosphatidylethanolamine at the phagophore expanding autophagic membranes. Other autophagy-related proteins such as Atg4, Atg12, Atg5, and Atg16 are also involved in the regulation of these pathways. The autophagosome travels through the cytoplasm of the cell to a lysosome, and the two organelles fuse; intersection with endosomal pathways also occurs.[11] Within the lysosome, the contents of the autophagosome are degraded via acidic lysosomal hydrolases.[16]

Microautophagy, on the other hand, involves the direct engulfment of cytoplasmic material into the lysosome.[17] This occurs by invagination, meaning the inward folding of the lysosomal membrane, or cellular protrusion.[13]

Chaperone-mediated autophagy, or CMA, is a very complex and specific pathway, which involves the recognition by the hsc70-containing complex.[13][18] This means that a protein must contain the recognition site for this hsc70 complex which will allow it to bind to this chaperone, forming the CMA- substrate/chaperone complex.[16] This complex then moves to the lysosomal membrane-bound protein that will recognise and bind with the CMA receptor, allowing it to enter the cell.[19] Upon recognition, the substrate protein gets unfolded and it is translocated across the lysosome membrane with the assistance of the lysosomal hsc70 chaperone.[10][11][19] CMA is significantly different from other types of autophagy because it translocates protein material in a one by one manner, and it is extremely selective about what material crosses the lysosomal barrier.[12][19]

Molecular biology[edit]

Autophagy is initiated by the ULK1 kinase complex which consists of ULK1, Atg13, Atg17 and receives stress signals from mTOR complex 1. Once the mTORC1 kinase activity is inhibited, autophagosome formation occurs.[20][21] This involves Vps34 which forms a complex with Beclin1 after interacting with Ambra, Bif1 and Bcl-2 which modulate its binding properties.[22] Binding to Vps34 is essential because of its lipid kinase activity.[22] Autophagosome formation also requires Atg12 and LC3, protein conjugation systems that resemble ubiquitin.[23] The LC3 system is important for transport and maturation of the autophagosome.[23] Once an autophagosome has matured, it fuses its external membrane with lysosomes to degrade its cargo.[22]

Depending on the location of the p53 tumor suppressor protein, it plays a different role in regulating autophagy as well. When in the nuclear region, p53 acts as a transcription factor in order to activate DRAM1 and Sestrin2 which activates autophagy.[24] In the cytoplasm, p53 inhibits autophagy. Thus, to induce autophagy, p53 is degraded through proteasomes.[25]

Functions[edit]

Nutrient starvation[edit]

Autophagy has roles in various cellular functions. One particular example is in yeasts, where the nutrient starvation induces a high level of autophagy. This allows unneeded proteins to be degraded and the amino acids recycled for the synthesis of proteins that are essential for survival.[26][27][28] In higher eukaryotes, autophagy is induced in response to the nutrient depletion that occurs in animals at birth after severing of the trans-placental food supply, as well as that of nutrient starved cultured cells and tissues.[29][30] Mutant yeast cells that have a reduced autophagic capability rapidly perish in nutrition-deficient conditions.[31] Studies on the apg mutants suggest that autophagy via autophagic bodies is indispensable for protein degradation in the vacuoles under starvation conditions, and that at least 15 APG genes are involved in autophagy in yeast.[31] A gene known as Atg7 has been implicated in nutrient-mediated autophagy, as mice studies have shown that starvation-induced autophagy was impaired in Atg7-deficient mice.[30]

Infection[edit]

Autophagy has been recognized as an immune mechanism. It plays a role in the destruction of intracellular pathogens, in a process of degradation of dysfunctional intracellular organelles. Intracellular pathogens such as Mycobacterium tuberculosis, the bacterium which is responsible for tuberculosis, can survive within the cells by blocking the maturation of their phagosomes into degradative organelles called phagolysosomes.[32] Stimulation of autophagy in infected cells helps overcome the block and aids the cell to eliminate the pathogens. Vesicular stomatitis virus is believed to be taken up by the autophagosome from the cytosol and translocated to the endosomes where detection takes place by a member of the PRRs called toll-like receptor 7, detecting single stranded RNA. Following activation of the toll-like receptor, intracellular signaling cascades are initiated, leading to induction of interferon and other antiviral cytokines. A subset of viruses and bacteria subvert the autophagic pathway to promote their own replication.[33] Galectin-8 has recently been identified as an intracellular "danger receptor", able to initiate autophagy against intracellular pathogens. When galectin-8 binds to a damaged vacuole, it recruits autophagy adaptor such as NDP52 leading to the formation of an autophagosome and bacterial degradation.[34]

Repair mechanism[edit]

Autophagy degrades damaged organelles, cell membranes and proteins, and the failure of autophagy is thought to be one of the main reasons for the accumulation of cell damage and aging.[35]

Programmed cell death[edit]

One of the mechanisms of programmed cell death (PCD) is associated with the appearance of autophagosomes and depends on autophagy proteins. This form of cell death most likely corresponds to a process that has been morphologically defined as autophagic PCD.[36][36] One question that constantly arises, however, is whether autophagic activity in dying cells is the cause of death or is actually an attempt to prevent it. Morphological and histochemical studies so far did not prove a causative relationship between the autophagic process and cell death. In fact, there have recently been strong arguments that autophagic activity in dying cells might actually be a survival mechanism.[36] Studies of the metamorphosis of insects have shown cells undergoing a form of PCD that appears distinct from other forms; these have been proposed as examples of autophagic cell death.[37]

Autophagy and caloric restriction[edit]

Research suggests that autophagy is required for the lifespan-prolonging effects of caloric restriction.[38] A 2010 French study of nematodes, mice and flies showed that inhibition of autophagy exposed cells to metabolic stress. Resveratrol and the dietary restriction prolonged the lifespan of normal, autophagy-proficient nematodes, but not of nematodes in which autophagy had been inhibited by knocking out Beclin 1 (a known autophagic modulator).[38] Research is ongoing in this field.

Autophagy and exercise[edit]

Autophagy is essential for basal homeostasis; it is also extremely important in maintaining muscle homeostasis during physical exercise.[39][40] Although the molecular level of this research is only partially understood, it is understood in the study of mice that autophagy is important for the ever changing demands in nutritional and energy needs of exercise, particularly through the metabolic pathways of protein catabolism.[39][40] In a 2012 study conducted by the University of Texas Southwestern Medical Center in Dallas, mutant mice with a knock-in mutation of BCL2 phosphorylation sites to produce progeny that showed normal levels of basal autophagy yet were deficient in stress-induced autophagy were tested to challenge this theory.[39] Results showed that when compared to a control group (physiologically normal/unchanged), these mice illustrated a decrease in endurance and altered glucose metabolism during acute exercise.[39]

Another study demonstrated that skeletal muscle fibres of collagen VI knockout mice showed signs of degeneration due to an insufficiency of autophagy and this led to an accumulation of damaged mitochondria and excessive apoptosis.[41] Exercise induced autophagy is unsuccessful however; when autophagy was induced post-exercise artificially, the accumulation of damaged organelles in collagen VI deficient muscle fibres was prevented and cellular homeostasis was maintained.[41] Both studies demonstrate that autophagy induction may contribute to the beneficial metabolic effects of exercise and that it is essential in the maintaining muscle homeostasis during exercise, particularly in collagen VI fibres.[39][40][41]

Work at the Institute for Cell Biology, University of Bonn, showed that a certain type of autophagy, i.e., chaperone-assisted selective autophagy (CASA), is induced in contracting muscles and is required for maintaining the muscle sarcomere under mechanical tension.[42] The CASA chaperone complex recognizes mechanically damaged cytoskeleton components and directs these components through a ubiquitin-dependent autophagic sorting pathway to lysosomes for disposal. This is necessary for maintaining muscle activity.[42][43]

Autophagy and cancer[edit]

Oftentimes, cancer occurs when several different pathways that regulate cell differentiation are disturbed. Autophagy plays an important role in cancer – both in protecting against cancer as well as potentially contributing to the growth of cancer.[44] Autophagy may protect against cancer by isolating damaged organelles, allowing cell differentiation, increasing protein catabolism, and even promoting cell death of cancerous cells.[45] However, autophagy can also contribute to cancer by promoting survival of tumor cells that have been starved[citation needed].

The role of autophagy in cancer is one that has been highly researched and reviewed. There is evidence that emphasizes the role of autophagy both as a tumor suppressor as well as a factor in tumor cell survival. However, recent research has been able to show that autophagy is more likely to be used as a tumor suppressor according to several models.[44]

Tumor Suppressor[edit]

In order to maintain homeostasis conditions, autophagy must not be disrupted. If this important mechanism is interrupted, tumor growth can likely occur. The main function of autophagy in tumor suppression is its ability to remove damaged proteins and organelles thus limiting any cell growth instability.[45] Several experiments have been done with mice and varying Beclin1, a protein that regulates autophagy. When the Beclin1 gene was altered to be heterozygous (Beclin 1+/-), the mice were found to be tumor prone.[46] However, when Beclin1 was overexpressed, tumor development was inhibited.[47]

Another study done on p62 further emphasizes autophagy’s role in tumor suppression. The increase of p62/SQSTM 1 protein groups due to lack of autophagy, damaged mitochondria, and defected misfolded proteins lead to reactive oxygen species (ROS) production.[45] ROS leads to damaged DNA and thus the formation of unwanted tumor cells.[45]

Necrosis and chronic inflammation also has been shown to be limited through autophagy which helps protect against the formation of tumor cells. Thus these experiments show autophagy’s role as a tumor suppressor.[48]

Tumor Cell Survival[edit]

Alternatively, autophagy has also been shown to play a huge role in tumor cell survival. In cancerous cells, autophagy is used as a way to deal with stress on the cell.[49] Once these autophagy related genes were inhibited, cell death was potentiated.[50] Tumor cells have high metabolic demands due to the increase in cell proliferation.[45] The increase in metabolic energy is offset by autophagy functions. These metabolic stresses include hypoxia, nutrient deprivation, and an increase in proliferation. These stresses activate autophagy in order to recycle ATP and maintain survival of the cancerous cells.[51] Autophagy has been shown to enable continued growth of tumor cells by maintaining cellular energy production. By inhibiting autophagy genes in these tumors cells, regression of the tumor and extended survival of the organs affected by the tumors were found. Furthermore, inhibition of autophagy has also been shown to enhance the effectiveness of anticancer therapies.[51]

Mechanism of Cell Death[edit]

Cells that undergo an extreme amount of stress experience cell death either through apoptosis or other mechanisms. Prolonged autophagy activation leads to a high turnover rate of proteins and different organelles. This high rate above the survival threshold may kill cancer cells with a high apoptotic threshold.[51] This technique can be utilized as a therapeutic cancer treatment.

Therapeutic Target[edit]

New developments in research have found that targeting autophagy may be a viable new therapeutic solution in fighting cancer. As discussed above, autophagy plays both a role in tumor suppression and tumor cell survival. Thus, these qualities about autophagy can be used and manipulated as a strategy for cancer prevention. The first strategy is to induce autophagy and enhance its tumor suppression attributes. The second strategy is to inhibit autophagy and thus induce apoptosis.[50]

The first strategy has been viewed and tested by looking at dose-response antitumor effects in autophagy-inducing therapies. These therapies have shown that autophagy extent increases in a dose-dependent manner. This is directly related to the growth of cancer cells in a dose-dependent manner as well.[49] Therefore, this data supports the development of therapies that will encourage autophagy. Inhibiting the protein pathways directly known to induce autophagy may serve as another anticancer therapy.[50] Lastly, overexpression of autophagy genes can be used.[50]

The second strategy is based on the idea that autophagy is a protein degradation system used to maintain homeostasis and the findings that inhibition of autophagy often leads to apoptosis. Inhibition of autophagy is riskier because it may lead to cell survival instead of the desired cell death.[49] This method requires much more testing.

See also[edit]

References[edit]

  1. ^ a b c Lin NY, Beyer C, Gießl A, et al. (September 2012). "Autophagy regulates TNFα-mediated joint destruction in experimental arthritis". Ann. Rheum. Dis. 72 (5): 761–8. doi:10.1136/annrheumdis-2012-201671. PMID 22975756. 
  2. ^ a b Patel AS, Lin L, Geyer A, et al. (2012). "Autophagy in idiopathic pulmonary fibrosis". In Eickelberg, Oliver. PLoS ONE 7 (7): e41394. doi:10.1371/journal.pone.0041394. PMC 3399849. PMID 22815997. 
  3. ^ Peracchio C, Alabiso O, Valente G, Isidoro C (September 2012). "Involvement of autophagy in ovarian cancer: a working hypothesis". J Ovarian Res 5 (1): 22. doi:10.1186/1757-2215-5-22. PMC 3506510. PMID 22974323. 
  4. ^ a b Klionsky, DJ (2008). "Autophagy revisited: A conversation with Christian de Duve". Autophagy 4 (6): 740–3. PMID 18567941. 
  5. ^ Ashford, TP; Porter, KR (1962). "Cytoplasmic components in hepatic cell lysosomes". The Journal of Cell Biology 12 (1): 198–202. doi:10.1083/jcb.12.1.198. PMC 2106008. PMID 13862833. 
  6. ^ Deter, RL; Baudhuin, P; De Duve, C (1967). "Participation of lysosomes in cellular autophagy induced in rat liver by glucagon". The Journal of Cell Biology 35 (2): C11–6. PMC 2107130. PMID 6055998. 
  7. ^ Deter, RL; De Duve, C (1967). "Influence of glucagon, an inducer of cellular autophagy, on some physical properties of rat liver lysosomes". The Journal of Cell Biology 33 (2): 437–49. PMC 2108350. PMID 4292315. 
  8. ^ De Duve, C (1983). "Lysosomes revisited". European journal of biochemistry / FEBS 137 (3): 391–7. doi:10.1111/j.1432-1033.1983.tb07841.x. PMID 6319122. 
  9. ^ William A. Dunn Jr., Laura A. Schroder, John P. Aris (2013). "Historical overview of autophagy". In Hong-Gang Wang. Autophagy and Cancer. Springer. pp. 3–4. ISBN 9781461465614. 
  10. ^ a b Lee J, Giordano S, Zhang J (January 2012). "Autophagy, mitochondria and oxidative stress: cross-talk and redox signalling". Biochem. J. 441 (2): 523–40. doi:10.1042/BJ20111451. PMC 3258656. PMID 22187934. 
  11. ^ a b c d Mizushima N, Ohsumi Y, Yoshimori T (December 2002). "Autophagosome formation in mammalian cells". Cell Struct. Funct. 27 (6): 421–9. doi:10.1247/csf.27.421. PMID 12576635. 
  12. ^ a b Levine B, Mizushima N, Virgin HW (January 2011). "Autophagy in immunity and inflammation". Nature 469 (7330): 323–35. doi:10.1038/nature09782. PMC 3131688. PMID 21248839. 
  13. ^ a b c Česen MH, Pegan K, Spes A, Turk B (July 2012). "Lysosomal pathways to cell death and their therapeutic applications". Exp. Cell Res. 318 (11): 1245–51. doi:10.1016/j.yexcr.2012.03.005. PMID 22465226. 
  14. ^ Lee JS, Kim YJ, Kim CL, Lee GM (September 2012). "Differential induction of autophagy in caspase-3/7 down-regulating and Bcl-2 overexpressing recombinant CHO cells subjected to sodium butyrate treatment". J. Biotechnol. 161 (1): 34–41. doi:10.1016/j.jbiotec.2012.05.011. PMID 22728390. 
  15. ^ Zhu, JH; Horbinski, C; Guo, F; Watkins, S; Uchiyama, Y; Chu, CT (January 2007). "Regulation of autophagy by extracellular signal-regulated protein kinases during 1-methyl-4-phenylpyridinium-induced cell death". The American journal of pathology 170 (1): 75–86. doi:10.2353/ajpath.2007.060524. PMC 1762689. PMID 17200184. 
  16. ^ a b Homma, K.S. et al (2011). Autophagy Database http://tp-apg.genes.nig.ac.jp/autophagy/list/GeneList.html |url= missing title (help). Retrieved 2012-10-08 
  17. ^ "The Discovery of Lysosomes and Autophagy". 49 3: 49. 2010 
  18. ^ Bandyopadhyay U, Kaushik S, Varticovski L, Cuervo AM (September 2008). "The chaperone-mediated autophagy receptor organizes in dynamic protein complexes at the lysosomal membrane". Mol. Cell. Biol. 28 (18): 5747–63. doi:10.1128/MCB.02070-07. PMC 2546938. PMID 18644871. 
  19. ^ a b c Perry, A. (2010). Wiley & Sons Ltd, Chichester 115 (11): 0 
  20. ^ Jung CH, Jun CB, Ro SH, Kim YM, Otto NM, Cao J et al. (2009). "ULK-Atg13-FIP200 complexes mediate mTOR signaling to the autophagy machinery". Mol Biol Cell 20 (7): 1992–2003. doi:10.1091/mbc.E08-12-1249. PMC 2663920. PMID 19225151. 
  21. ^ Mizushima N (2010). "The role of the Atg1/ULK1 complex in autophagy regulation". Curr Opin Cell Biol 22 (2): 132–9. doi:10.1016/j.ceb.2009.12.004. PMID 20056399. 
  22. ^ a b c Pattingre S, Espert L, Biard-Piechaczyk M, Codogno P (2008). "Regulation of macroautophagy by mTOR and Beclin 1 complexes". Biochimie 90 (2): 313–23. doi:10.1016/j.biochi.2007.08.014. PMID 17928127. 
  23. ^ a b Matsushita M, Suzuki NN, Obara K, Fujioka Y, Ohsumi Y, Inagaki F (2007). "Structure of Atg5.Atg16, a complex essential for autophagy". J Biol Chem 282 (9): 6763–72. doi:10.1074/jbc.M609876200. PMID 17192262. 
  24. ^ Maiuri MC, Malik SA, Morselli E, Kepp O, Criollo A, Mouchel PL et al. (2009). "Stimulation of autophagy by the p53 target gene Sestrin2". Cell Cycle 8 (10): 1571–6. doi:10.4161/cc.8.10.8498. PMID 19377293. 
  25. ^ Tasdemir E, Maiuri MC, Galluzzi L, Vitale I, Djavaheri-Mergny M, D'Amelio M et al. (2008). "Regulation of autophagy by cytoplasmic p53". Nat Cell Biol 10 (6): 676–87. doi:10.1038/ncb1730. PMC 2676564. PMID 18454141. 
  26. ^ Reggiori F, Klionsky DJ (February 2002). "Autophagy in the eukaryotic cell". Eukaryotic Cell 1 (1): 11–21. doi:10.1128/EC.01.1.11-21.2002. PMC 118053. PMID 12455967. 
  27. ^ N.Y. (2000). "Autophagy as a regulated pathway of cellular degradation". Klionsky, D. J. & Emr, S. D. Autophagy as a regulated pathway of cellular degradation 290: 1717–1721 
  28. ^ Levine B, Klionsky DJ (April 2004). "Development by self-digestion: molecular mechanisms and biological functions of autophagy". Dev. Cell 6 (4): 463–77. doi:10.1016/S1534-5807(04)00099-1. PMID 15068787. 
  29. ^ Kuma A, Hatano M, Matsui M, et al. (December 2004). "The role of autophagy during the early neonatal starvation period". Nature 432 (7020): 1032–6. doi:10.1038/nature03029. PMID 15525940. 
  30. ^ a b Mizushima N, Yamamoto A, Matsui M, Yoshimori T, Ohsumi Y (March 2004). "In vivo analysis of autophagy in response to nutrient starvation using transgenic mice expressing a fluorescent autophagosome marker". Mol. Biol. Cell 15 (3): 1101–11. doi:10.1091/mbc.E03-09-0704. PMC 363084. PMID 14699058. 
  31. ^ a b Tsukada M, Ohsumi Y (October 1993). "Isolation and characterization of autophagy-defective mutants of Saccharomyces cerevisiae". FEBS Lett. 333 (1–2): 169–74. doi:10.1016/0014-5793(93)80398-E. PMID 8224160. 
  32. ^ Deretic V, Delgado M, Vergne I, et al. (2009). "Autophagy in immunity against mycobacterium tuberculosis: a model system to dissect immunological roles of autophagy". Curr. Top. Microbiol. Immunol. Current Topics in Microbiology and Immunology 335: 169–88. doi:10.1007/978-3-642-00302-8_8. ISBN 978-3-642-00301-1. PMC 2788935. PMID 19802565. 
  33. ^ Jackson WT, Giddings TH, Taylor MP, et al. (May 2005). "Subversion of cellular autophagosomal machinery by RNA viruses". PLoS Biol. 3 (5): e156. doi:10.1371/journal.pbio.0030156. PMC 1084330. PMID 15884975. 
  34. ^ Thurston TL, Wandel MP, von Muhlinen N, Foeglein A, Randow F (February 2012). "Galectin 8 targets damaged vesicles for autophagy to defend cells against bacterial invasion". Nature 482 (7385): 414–8. doi:10.1038/nature10744. PMC 3343631. PMID 22246324. 
  35. ^ Cuervo AM, Bergamini E, Brunk UT, Dröge W, Ffrench M, Terman A (2005). "Autophagy and aging: the importance of maintaining "clean" cells". Autophagy 1 (3): 131–40. doi:10.4161/auto.1.3.2017. PMID 16874025. 
  36. ^ a b c Tsujimoto Y, Shimizu S (November 2005). "Another way to die: autophagic programmed cell death". Cell Death Differ. 12 (Suppl 2): 1528–34. doi:10.1038/sj.cdd.4401777. PMID 16247500. 
  37. ^ Schwartz LM, Smith SW, Jones ME, Osborne BA (February 1993). "Do all programmed cell deaths occur via apoptosis?". Proc. Natl. Acad. Sci. U.S.A. 90 (3): 980–4. doi:10.1073/pnas.90.3.980. PMC 45794. PMID 8430112. 
  38. ^ a b Morselli E, Maiuri MC, Markaki M, et al. (2010). "Caloric restriction and resveratrol promote longevity through the Sirtuin-1-dependent induction of autophagy". Cell Death Dis 1 (1): e10–. doi:10.1038/cddis.2009.8. PMC 3032517. PMID 21364612. 
  39. ^ a b c d e He C, Bassik MC, Moresi V, et al. (January 2012). "Exercise-induced BCL2-regulated autophagy is required for muscle glucose homeostasis". Nature 481 (7382): 511–5. doi:10.1038/nature10758. PMC 3518436. PMID 22258505. 
  40. ^ a b c Nair U, Klionsky DJ (December 2011). "Activation of autophagy is required for muscle homeostasis during physical exercise". Autophagy 7 (12): 1405–6. doi:10.4161/auto.7.12.18315. PMC 3288013. PMID 22082869. 
  41. ^ a b c Grumati P, Coletto L, Schiavinato A, et al. (December 2011). "Physical exercise stimulates autophagy in normal skeletal muscles but is detrimental for collagen VI-deficient muscles". Autophagy 7 (12): 1415–23. doi:10.4161/auto.7.12.17877. PMC 3288016. PMID 22024752. 
  42. ^ a b Arndt V, Dick N, Tawo R, Dreiseidler M, Wenzel D, Hesse M, Fürst DO, Saftig P, Saint R, Fleischmann BK, Hoch M, Höhfeld J (January 2010). "Chaperone-assisted selective autophagy is essential for muscle maintenance". Curr Biol 20 (2): 143–8. doi:10.1016/j.cub.2009.11.022. PMID 20060297. 
  43. ^ Ulbricht A, Eppler FJ, Tapia VE, van der Ven PF, Hampe N, Hersch N, Vakeel P, Stadel D, Haas A, Saftig P, Behrends C, Fürst DO, Volkmer R, Hoffmann B, Kolanus W, Höhfeld J. (February 2013). "Cellular Mechanotransduction Relies on Tension-Induced and Chaperone-Assisted Autophagy". Curr Biol 23 (5): 430–5. doi:10.1016/j.cub.2013.01.064. PMID 23434281. 
  44. ^ a b Furuya, N., Liang, X.H., and Levin, B. 2004. Autophagy and cancer. In Autophagy. D.J. Klionsky editor. Landes Bioscience. Georgetown, Texas, USA. 244-253.
  45. ^ a b c d e Mathew R, Karp CM, Beaudoin B, Vuong N, Chen G, Chen HY et al. (2009). "Autophagy suppresses tumorigenesis through elimination of p62". Cell 137 (6): 1062–75. doi:10.1016/j.cell.2009.03.048. PMC 2802318. PMID 19524509. 
  46. ^ Qu X, Yu J, Bhagat G, Furuya N, Hibshoosh H, Troxel A et al. (2003). "Promotion of tumorigenesis by heterozygous disruption of the beclin 1 autophagy gene". J Clin Invest 112 (12): 1809–20. doi:10.1172/JCI20039. PMC 297002. PMID 14638851. 
  47. ^ Liang XH, Jackson S, Seaman M, Brown K, Kempkes B, Hibshoosh H et al. (1999). "Induction of autophagy and inhibition of tumorigenesis by beclin 1". Nature 402 (6762): 672–6. doi:10.1038/45257. PMID 10604474. 
  48. ^ Duran A, Linares JF, Galvez AS, Wikenheiser K, Flores JM, Diaz-Meco MT et al. (2008). "The signaling adaptor p62 is an important NF-kappaB mediator in tumorigenesis". Cancer Cell 13 (4): 343–54. doi:10.1016/j.ccr.2008.02.001. PMID 18394557. 
  49. ^ a b c Paglin S, Hollister T, Delohery T, Hackett N, McMahill M, Sphicas E, Domingo D, Yahalom J. A novel response of cancer cells to radiation involves autophagy and formation of acidic vesicles" Cancer Res 2001; 61:439-44.
  50. ^ a b c d Jin S, White E. Role of autophagy in cancer: management of metabolic stress" Autophagy2007;3:28–31.
  51. ^ a b c Yang ZJ, Chee CE, Huang S, Sinicrope FA. The role of autophagy in cancer: therapeutic implications. Mol Cancer Ther. 2011;10:1533–1541. doi:10.1158/1535-7163.MCT-11-0047

External links[edit]

Further reading[edit]

External links[edit]