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      Forever Young: Mechanisms of Natural Anoxia Tolerance and Potential Links to Longevity

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      Oxidative Medicine and Cellular Longevity
      Informa UK Limited

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          Abstract

          While mammals cannot survive oxygen deprivation for more than a few minutes without sustaining severe organ damage, some animals have mastered anaerobic life. Freshwater turtles belonging to the Trachemys and Chrysemys genera are the champion facultative anaerobes of the vertebrate world, often surviving without oxygen for many weeks at a time. The physiological and biochemical mechanisms that underlie anoxia tolerance in turtles include profound metabolic rate depression, post-translational modification of proteins, strong antioxidant defenses, activation of specific stress-responsive transcription factors, and enhanced expression of cyto-protective proteins. Turtles are also known for their incredible longevity and display characteristics of “negligible senescence.” We propose that the robust stress-tolerance mechanisms that permit long term anaerobiosis by turtles may also support the longevity of these animals. Many of the mechanisms involved in natural anoxia tolerance, such as hypometabolism or the induction of various protective proteins/pathways, have been shown to play important roles in mammalian oxygen-related diseases and improved understanding of how cells survive without oxygen could aid in the understanding and treatment of various pathological conditions that involve hypoxia or oxidative stress. In the present review we discuss the recent advances made in understanding the molecular nature of anoxia tolerance in turtles and the potential links between this tolerance and longevity.

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          Hsp70 chaperones: Cellular functions and molecular mechanism

          Abstract. Hsp70 proteins are central components of the cellular network of molecular chaperones and folding catalysts. They assist a large variety of protein folding processes in the cell by transient association of their substrate binding domain with short hydrophobic peptide segments within their substrate proteins. The substrate binding and release cycle is driven by the switching of Hsp70 between the low-affinity ATP bound state and the high-affinity ADP bound state. Thus, ATP binding and hydrolysis are essential in vitro and in vivo for the chaperone activity of Hsp70 proteins. This ATPase cycle is controlled by co-chaperones of the family of J-domain proteins, which target Hsp70s to their substrates, and by nucleotide exchange factors, which determine the lifetime of the Hsp70-substrate complex. Additional co-chaperones fine-tune this chaperone cycle. For specific tasks the Hsp70 cycle is coupled to the action of other chaperones, such as Hsp90 and Hsp100.
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            Bcl-2 functions in an antioxidant pathway to prevent apoptosis.

            Bcl-2 inhibits most types of apoptotic cell death, implying a common mechanism of lethality. Bcl-2 is localized to intracellular sites of oxygen free radical generation including mitochondria, endoplasmic reticula, and nuclear membranes. Antioxidants that scavenge peroxides, N-acetylcysteine and glutathione peroxidase, countered apoptotic death, while manganese superoxide dismutase did not. Bcl-2 protected cells from H2O2- and menadione-induced oxidative deaths. Bcl-2 did not prevent the cyanide-resistant oxidative burst generated by menadione. Two model systems of apoptosis showed no increment in cyanide-resistant respiration, and generation of endogenous peroxides continued at an inherent rate that was unaltered by Bcl-2. Following an apoptotic signal, cells sustained progressive lipid peroxidation. Overexpression of Bcl-2 functioned to suppress lipid peroxidation completely. We propose a model in which Bcl-2 regulates an antioxidant pathway at sites of free radical generation.
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              Proteotoxic stress and inducible chaperone networks in neurodegenerative disease and aging.

              The long-term health of the cell is inextricably linked to protein quality control. Under optimal conditions this is accomplished by protein homeostasis, a highly complex network of molecular interactions that balances protein biosynthesis, folding, translocation, assembly/disassembly, and clearance. This review will examine the consequences of an imbalance in homeostasis on the flux of misfolded proteins that, if unattended, can result in severe molecular damage to the cell. Adaptation and survival requires the ability to sense damaged proteins and to coordinate the activities of protective stress response pathways and chaperone networks. Yet, despite the abundance and apparent capacity of chaperones and other components of homeostasis to restore folding equilibrium, the cell appears poorly adapted for chronic proteotoxic stress when conformationally challenged aggregation-prone proteins are expressed in cancer, metabolic disease, and neurodegenerative disease. The decline in biosynthetic and repair activities that compromises the integrity of the proteome is influenced strongly by genes that control aging, thus linking stress and protein homeostasis with the health and life span of the organism.
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                Author and article information

                Journal
                Oxidative Medicine and Cellular Longevity
                Oxidative Medicine and Cellular Longevity
                Informa UK Limited
                1942-0900
                1942-0994
                2010
                2010
                : 3
                : 3
                : 186-198
                Article
                10.4161/oxim.3.3.12356
                20716943
                1acdf894-c644-495a-9299-fb6c80636f89
                © 2010

                http://creativecommons.org/licenses/by/3.0/

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