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Lu Y, Hao BX, Graeff R, Wong CWM, Wu WT, Yue J. Two pore channel 2 (TPC2) inhibits autophagosomal-lysosomal fusion by alkalinizing lysosomal pH. J Biol Chem 2013; 288:24247-63. [PMID: 23836916 PMCID: PMC3745369 DOI: 10.1074/jbc.m113.484253] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Autophagy is an evolutionarily conserved lysosomal degradation pathway, yet the underlying mechanisms remain poorly understood. Nicotinic acid adenine dinucleotide phosphate (NAADP), one of the most potent Ca2+ mobilizing messengers, elicits Ca2+ release from lysosomes via the two pore channel 2 (TPC2) in many cell types. Here we found that overexpression of TPC2 in HeLa or mouse embryonic stem cells inhibited autophagosomal-lysosomal fusion, thereby resulting in the accumulation of autophagosomes. Treatment of TPC2 expressing cells with a cell permeant-NAADP agonist, NAADP-AM, further induced autophagosome accumulation. On the other hand, TPC2 knockdown or treatment of cells with Ned-19, a NAADP antagonist, markedly decreased the accumulation of autophagosomes. TPC2-induced accumulation of autophagosomes was also markedly blocked by ATG5 knockdown. Interestingly, inhibiting mTOR activity failed to increase TPC2-induced autophagosome accumulation. Instead, we found that overexpression of TPC2 alkalinized lysosomal pH, and lysosomal re-acidification abolished TPC2-induced autophagosome accumulation. In addition, TPC2 overexpression had no effect on general endosomal-lysosomal degradation but prevented the recruitment of Rab-7 to autophagosomes. Taken together, our data demonstrate that TPC2/NAADP/Ca2+ signaling alkalinizes lysosomal pH to specifically inhibit the later stage of basal autophagy progression.
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Affiliation(s)
- Yingying Lu
- Department of Physiology, University of Hong Kong, Hong Kong, China
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152
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Tsuzuki T, Sakaguchi N, Kudoh T, Takano S, Uehara M, Murayama T, Sakurai T, Hashii M, Higashida H, Weber K, Guse AH, Kameda T, Hirokawa T, Kumaki Y, Potter BVL, Fukuda H, Arisawa M, Shuto S. Design and Synthesis of Cyclic ADP-4-Thioribose as a Stable Equivalent of Cyclic ADP-Ribose, a Calcium Ion-Mobilizing Second Messenger. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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153
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Abstract
Cytoplasmic Ca(2+) is an universal intracellular messenger that activates cellular responses over a broad temporal range, from neurotransmitter release to cell growth and proliferation. Inherent to the use of the multifarious Ca(2+) signal is the question of specificity: how can some Ca(2+)-dependent responses be activated in a cell and not others? A rise in cytoplasmic Ca(2+) can evoke a response either by binding directly to the target (as occurs with certain Ca(2+)-activated K(+) and Cl(-) channels, for example) or through recruitment of intermediary proteins, such as calmodulin and troponin C. A substantial body of evidence has now established that Ca(2+)-binding proteins differ both in their affinities for Ca(2+) and in their on- and off-rates for Ca(2+) binding/unbinding. Furthermore, different Ca(2+)-binding proteins often occupy distinct locations within the cell. Therefore, the size, kinetics and spatial profile of a cytoplasmic Ca(2+) signal are all important in determining which Ca(2+)-dependent response will be activated, when and for how long.
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Affiliation(s)
- Pulak Kar
- Department of Physiology, Anatomy and Genetics; University of Oxford; Oxford, UK
| | - Anant Parekh
- Department of Physiology, Anatomy and Genetics; University of Oxford; Oxford, UK
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154
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Zhang ZH, Lu YY, Yue J. Two pore channel 2 differentially modulates neural differentiation of mouse embryonic stem cells. PLoS One 2013; 8:e66077. [PMID: 23776607 PMCID: PMC3680454 DOI: 10.1371/journal.pone.0066077] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 05/01/2013] [Indexed: 12/15/2022] Open
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) is an endogenous Ca2+ mobilizing nucleotide presented in various species. NAADP mobilizes Ca2+ from acidic organelles through two pore channel 2 (TPC2) in many cell types and it has been previously shown that NAADP can potently induce neuronal differentiation in PC12 cells. Here we examined the role of TPC2 signaling in the neural differentiation of mouse embryonic stem (ES) cells. We found that the expression of TPC2 was markedly decreased during the initial ES cell entry into neural progenitors, and the levels of TPC2 gradually rebounded during the late stages of neurogenesis. Correspondingly, TPC2 knockdown accelerated mouse ES cell differentiation into neural progenitors but inhibited these neural progenitors from committing to neurons. Overexpression of TPC2, on the other hand, inhibited mouse ES cell from entering the early neural lineage. Interestingly, TPC2 knockdown had no effect on the differentiation of astrocytes and oligodendrocytes of mouse ES cells. Taken together, our data indicate that TPC2 signaling plays a temporal and differential role in modulating the neural lineage entry of mouse ES cells, in that TPC2 signaling inhibits ES cell entry to early neural progenitors, but is required for late neuronal differentiation.
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Affiliation(s)
- Zhe-Hao Zhang
- Department of Physiology, University of Hong Kong, Hong Kong, China
| | - Ying-Ying Lu
- Department of Physiology, University of Hong Kong, Hong Kong, China
| | - Jianbo Yue
- Department of Physiology, University of Hong Kong, Hong Kong, China
- * E-mail:
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155
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Mouchiroud L, Houtkooper RH, Auwerx J. NAD⁺ metabolism: a therapeutic target for age-related metabolic disease. Crit Rev Biochem Mol Biol 2013; 48:397-408. [PMID: 23742622 DOI: 10.3109/10409238.2013.789479] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Nicotinamide adenine dinucleotide (NAD) is a central metabolic cofactor by virtue of its redox capacity, and as such regulates a wealth of metabolic transformations. However, the identification of the longevity protein silent regulator 2 (Sir2), the founding member of the sirtuin protein family, as being NAD⁺-dependent reignited interest in this metabolite. The sirtuins (SIRT1-7 in mammals) utilize NAD⁺ to deacetylate proteins in different subcellular compartments with a variety of functions, but with a strong convergence on optimizing mitochondrial function. Since cellular NAD⁺ levels are limiting for sirtuin activity, boosting its levels is a powerful means to activate sirtuins as a potential therapy for mitochondrial, often age-related, diseases. Indeed, supplying excess precursors, or blocking its utilization by poly(ADP-ribose) polymerase (PARP) enzymes or CD38/CD157, boosts NAD⁺ levels, activates sirtuins and promotes healthy aging. Here, we discuss the current state of knowledge of NAD⁺ metabolism, primarily in relation to sirtuin function. We highlight how NAD⁺ levels change in diverse physiological conditions, and how this can be employed as a pharmacological strategy.
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Affiliation(s)
- Laurent Mouchiroud
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Riekelt H Houtkooper
- Laboratory Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands
| | - Johan Auwerx
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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156
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Dölle C, Rack JGM, Ziegler M. NAD and ADP-ribose metabolism in mitochondria. FEBS J 2013; 280:3530-41. [PMID: 23617329 DOI: 10.1111/febs.12304] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/18/2013] [Accepted: 04/23/2013] [Indexed: 12/29/2022]
Abstract
Mitochondrial metabolism is intimately connected to the universal coenzyme NAD. In addition to its role in redox reactions of energy transduction, NAD serves as substrate in regulatory reactions that lead to its degradation. Importantly, all types of the known NAD-consuming signalling reactions have been reported to take place in mitochondria. These reactions include the generation of second messengers, as well as post-translational protein modifications such as ADP-ribosylation and protein deacetylation. Therefore, the availability and redox state of NAD emerged as important factors in the regulation of mitochondrial metabolism. Molecular mechanisms and targets of mitochondrial NAD-dependent protein deacetylation and mono-ADP-ribosylation have been established, whereas poly-ADP-ribosylation and NAD-derived messenger generation in the organelles await in-depth characterization. In this review, we highlight the major NAD-dependent reactions occurring within mitochondria and describe their metabolic and regulatory functions. We also discuss the metabolic fates of the NAD-degradation products, nicotinamide and ADP-ribose, and how the mitochondrial NAD pool is restored.
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Affiliation(s)
- Christian Dölle
- Department of Molecular Biology, University of Bergen, Bergen, Norway
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157
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Tsuzuki T, Sakaguchi N, Kudoh T, Takano S, Uehara M, Murayama T, Sakurai T, Hashii M, Higashida H, Weber K, Guse AH, Kameda T, Hirokawa T, Kumaki Y, Potter BVL, Fukuda H, Arisawa M, Shuto S. Design and synthesis of cyclic ADP-4-thioribose as a stable equivalent of cyclic ADP-ribose, a calcium ion-mobilizing second messenger. Angew Chem Int Ed Engl 2013; 52:6633-7. [PMID: 23670921 PMCID: PMC3738939 DOI: 10.1002/anie.201302098] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Indexed: 11/23/2022]
Affiliation(s)
- Takayoshi Tsuzuki
- Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-ku, Sapporo 060-0812, Japan
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158
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Ramos I, Wessel GM. Calcium pathway machinery at fertilization in echinoderms. Cell Calcium 2012; 53:16-23. [PMID: 23218671 DOI: 10.1016/j.ceca.2012.11.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/07/2012] [Accepted: 11/09/2012] [Indexed: 01/01/2023]
Abstract
Calcium signaling in cells directs diverse physiological processes. The calcium waves triggered by fertilization is a highly conserved calcium signaling event essential for egg activation, and has been documented in every egg tested. This activity is one of the few highly conserved events of egg activation through the course of evolution. Echinoderm eggs, as well as many other cell types, have three main intracellular Ca(2+) mobilizing messengers - IP3, cADPR and NAADP. Both cADPR and NAADP were identified as Ca(2+) mobilizing messengers using the sea urchin egg homogenate, and this experimental system, along with the intact urchin and starfish oocyte/egg, continues to be a vital tool for investigating the mechanism of action of calcium signals. While many of the major regulatory steps of the IP3 pathway are well resolved, both cADPR and NAADP remain understudied in terms of our understanding of the fundamental process of egg activation at fertilization. Recently, NAADP has been shown to trigger Ca(2+) release from acidic vesicles, separately from the ER, and a new class of calcium channels, the two-pore channels (TPCs), was identified as the likely targets for this messenger. Moreover, it was found that both cADPR and NAADP can be synthesized by the same family of enzymes, the ADP-rybosyl cyclases (ARCs). In this context of increasing amount of information, the potential coupling and functional roles of different messengers, intracellular stores and channels in the formation of the fertilization calcium wave in echinoderms will be critically evaluated.
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Affiliation(s)
- Isabela Ramos
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, RI 02912, USA
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