粒腺體動力學由融合和裂變狀態組成，它們不僅調節粒腺體的質量和形態，而且還決定細胞的命運，例如細胞凋亡和細胞週期。因此，在本篇研究我們將重點放在研究粒腺體動力學上。我們利用光遺傳學方法來觸發粒腺體動力學。我們將光誘導蛋白通道鈣轉位通道視紫紅質（CatCh）轉染到細胞膜上，並利用刺激470 nm藍光照射來模擬鈣離子進入細胞內產生鈣離子振盪。我們可以透過各種參數（例如功率密度，頻率和作用時間）來精確控制光刺激。更詳細地講，利用定制的光刺激條件可以觸發獨特的鈣離子振盪波，從而觸發特定的信號通路。在這項研究中，作者以一個特定的條件區間去刺激帶有CatCh的細胞，並觀察透過光遺傳誘導的粒腺體動力學。結果證實進行光刺激刺激，粒腺體可以從融合狀態轉變為裂變狀態。不只如此，光刺激還觸發粒腺體裂變蛋白Drp1在Ser 616位點的磷酸化，並且不使抗粒腺體裂變蛋白Drp1-S637磷酸化。結果也指出，光刺激對粒腺體融合蛋白Mfn1和Mfn2沒有影響。此外，我們也找出了導致光遺傳學誘導的粒腺體裂變的上游信號途徑。總而言之，這項研究提供了一種有效且創新的方法來誘導粒腺體動態變化，在時間和空間維度上都具有更精確的控制以及分辨率

Mitochondrial dynamics consists of fusion and fission states, which regulate the quality and morphology of mitochondria in addition to determining the cellular events such as apoptosis and the cell cycle. Therefore, we focused on investigating mitochondrial dynamics in this study. We applied an optogenetic method to trigger mitochondrial dynamics and transfected the photo-inducible protein channel calcium translocating channelrhodopsin (CatCh) onto the cell membrane to mimic cytosolic calcium oscillation by 470-nm blue light illumination. The illumination could be precisely controlled by modifying various parameters such as power density, frequency, and duty cycle; more specifically, customized illumination conditions could trigger unique calcium oscillation waves to trigger specific signal pathways. In this study, the mitochondria were illuminated under optimal intervals of illumination parameters to observe optogenetic-induced mitochondrial dynamics. The results showed that application of illumination to cells expressing CatCh changed the mitochondrial dynamics from the fusion state to the fission state. Moreover, the illumination triggered phosphorylation at the Ser616 site of the mitochondrial fission protein Drp1 but did not phosphorylate the anti-mitochondrial fission protein Drp1-S637 and had no effects on the mitochondrial fusion proteins mitofusin-1 (Mfn1) and Mfn2. The results also allowed us to identify the candidate upstream signal pathways that cause optogenetics-induced mitochondrial fission. Thus, this study provides an effective and innovative method to control mitochondrial dynamics with a more precise resolution in both temporal and spatial dimensions.

Bo, T., Yamamori, T., Suzuki, M., Sakai, Y., Yamamoto, K., & Inanami, O. (2018). Calmodulin-dependent protein kinase II (CaMKII) mediates radiation-induced mitochondrial fission by regulating the phosphorylation of dynamin-related protein 1 (Drp1) at serine 616. Biochemical and Biophysical Research Communications, 495(2), 1601-1607.
Bossy, E., Barsoum, M. J., Godzik, A., Schwarzenbacher, R., & Lipton, S. A. (2003). Mitochondrial fission in apoptosis, neurodegeneration and aging. Current Opinion in Cell Biology, 15(6), 706-716.
Berridge, M., Michael, J., Martin, D., Bootman, H., & Llewelyn, R. H. (2003) Calcium signaling: dynamics, homeostasis and remodeling. Nature Reviews Molecular Cell Biology 4.7, 517-529.
Cereghetti, G. M., Stangherlin, A., De Brito, O. M., Chang, C. R., Blackstone, C., Bernardi, P., & Scorrano, L. (2008). Dephosphorylation by calcineurin regulates translocation of Drp1 to mitochondria. Proceedings of the National Academy of Sciences United States of America, 105(41), 15803-15808.
Chang, C. R., & Blackstone, C. (2007). Drp1 phosphorylation and mitochondrial regulation. EMBO Reports, 8(12), 1088-1089.
Chen, H., & Chan, D. C. (2009). Mitochondrial dynamics–fusion, fission, movement, and mitophagy in neurodegenerative diseases. Human Molecular Genetics, 18(R2), R169-R176.
Chen, H., & Chan, D. C. (2017). Mitochondrial dynamics in regulating the unique phenotypes of cancer and stem cells. Cell Metabolism, 26(1), 39-48.
Choi, S. Y., Huang, P., Jenkins, G. M., Chan, D. C., Schiller, J., & Frohman, M. A. (2006). A common lipid links Mfn-mediated mitochondrial fusion and SNARE-regulated exocytosis. Nature Cell Biology, 8(11), 1255-1262.
Cribbs, J.T. & Strack, S. (2007) Reversible phosphorylation of Drp1 by cyclic AMP-dependent protein kinase and calcineurin regulates mitochondrial fission and cell death. EMBO Reports, 8, 939-94.
Deisseroth, K. (2011) Optogenetics. Nature Methods 8, 26-29.
Deng, H., Dodson, M. W., Huang, H., & Guo, M. (2008). The Parkinson's disease genes pink1 and parkin promote mitochondrial fission and/or inhibit fusion in Drosophila. Proceedings of the National Academy of Sciences, 105(38), 14503-14508.
Gunter, T. E., Yule, D. I., Gunter, K. K., Eliseev, R. A., & Salter, J. D. (2004). Calcium and mitochondria. FEBS Letters, 567(1), 96-102.
Hama, N., Paliogianni, F., Fessler, B. J., & Boumpas, D. T. (1995). Calcium/calmodulin-dependent protein kinase II downregulates both calcineurin and protein kinase C-mediated pathways for cytokine gene transcription in human T cells. The Journal of Experimental Medicine, 181(3), 1217-1222.
Jiang, S., Chow, S. C., Nicotera, P., & Orrenius, S. (1994). Intracellular Ca2+ signals activate apoptosis in thymocytes: studies using the Ca2+-ATPase inhibitor thapsigargin. Experimental Cell Research, 212(1), 84-92.
Kaufman, R. J., & Jyoti, D. M. (2014). Calcium trafficking integrates endoplasmic reticulum function with mitochondrial bioenergetics. Biochimica et Biophysica Acta (BBA)-Molecular Cell Research, 1843.10, 2233-2239.
Khan, I., Tang, E., & Arany, P. (2015). Molecular pathway of near-infrared laser phototoxicity involves ATF-4 orchestrated ER stress. Scientific Reports, 5, 10581.
Kleinlogel, S., Feldbauer, K., Dempski, R. E., Fotis, H., Wood, P. G., Bamann, C., & Bamberg, E. (2011). Ultra light-sensitive and fast neuronal activation with the
Ca2+-permeable channelrhodopsin CatCh. Nature Neuroscience, 14(4), 513-518.
Ko, A. R., Hyun, H. W., Min, S. J., & Kim, J. E. (2016). The differential DRP1 phosphorylation and mitochondrial dynamics in the regional specific astroglial death induced by status epilepticus. Frontiers in Cellular Neuroscience, 10, 124.
Levskaya, A., Weiner, O. D., Lim, W. A., & Voigt, C. A. (2009). Spatiotemporal control of cell signaling using a light-switchable protein interaction. Nature, 461(7266), 997-1001.
Mohapatra, D. P., & Nau, C. (2005). Regulation of Ca2+-dependent desensitization in the vanilloid receptor TRPV1 by calcineurin and cAMP-dependent protein kinase. Journal of Biological Chemistry, 280(14), 13424-13432.
Nagel, G., Szellas, T., Huhn, W., Kateriya, S., Adeishvili, N., Berthold, P., & Bamberg, E. (2003). Channelrhodopsin-2, a directly light-gated cation-selective membrane channel. Proceedings of the National Academy of Sciences, 100(24), 13940-13945.
Parfitt, A.M., & Kleerekofer, M. (1980) The divalent ion homeostasis system: physiology and metabolism of calcium, phosphorus, magnesium, and bone. In: Maxwell M.H., Kleeman C.R., editors. Clinical Disorders of Fluid and Electrolyte Metabolism. McGraw-Hill, New York. 269-398.
Parone, P. A., Cruz, S., Tondera, D., Mattenberger, Y., James, D. I., Maechler, P., & Martinou, J. C. (2008). Preventing mitochondrial fission impairs mitochondrial function and leads to loss of mitochondrial DNA. PLoS ONE, 3(9), e3257.
Pastrana, E. (2011). Optogenetics: controlling cell function with light. Nature Methods, 8, 24–25.
Peng, J. Y., Lin, C. C., Chen, Y. J., Kao, L. S., Liu, Y. C., Chou, C. C., Huang, Y. H., Chang, F. R., Wu, Y. C., Tsai, Y. S., & Hsu, C. N. (2011). Automatic morphological subtyping reveals new roles of caspases in mitochondrial dynamics. PLoS Computational Biology, 7(10), e1002212.
Pinton, P., Giorgi, C., Siviero, R., Zecchini, E., & Rizzuto, R. (2008). Calcium and apoptosis: ER-mitochondria Ca2+ transfer in the control of apoptosis. Oncogene, 27(50), 6407-6418.
Rizzuto, R., De Stefani, D., Raffaello, A., & Mammucari, C. (2012). Mitochondria as sensors and regulators of calcium signaling. Nature Reviews Molecular Cell Biology, 13(9), 566-578.
Roe, A. J., & Qi, X. (2018). Drp1 phosphorylation by MAPK1 causes mitochondrial dysfunction in cell culture model of Huntington's disease. Biochemical and Biophysical Research Communications, 496(2), 706-711.
Sabouny, R., & Shutt, T. E. (2020). Reciprocal regulation of mitochondrial fission and fusion. Trends in Biochemical Sciences, 15, 235-259.
Spencer, D. M., Graef, I., Austin, D. J., Schreiber, S. L. & Crabtree, G. R. (1995). Proceedings of the National Academy of Sciences of the United States of America, 92, 9805-9809.
Toettcher, J., Voigt, C., Weiner, O. (2011). The promise of optogenetics in cell biology: interrogating molecular circuits in space and time. Nature Methods, 8, 35-38.
Wang, Z., Fan, M., Candas, D., Zhang, T. Q., Qin, L., Eldridge, A., & Duru, N. (2014). Cyclin B1/Cdk1 coordinates mitochondrial respiration for cell-cycle G2/M progression. Developmental Cell, 29(2), 217-232.
Westermann, B. (2010). Mitochondrial fusion and fission in cell life and death. Nature Reviews Molecular Cell Biology, 11(12), 872-884.
Wong, J., Abilez, O. J., & Kuhl, E. (2012). Computational optogenetics: a novel continuum framework for the photoelectrochemistry of living systems. Journal of the Mechanics and Physics of Solids, 60(6), 1158-1178.
Youle, R. J., & Karbowski, M. (2005). Mitochondrial fission in apoptosis. Nature reviews Molecular Cell Biology, 6(8), 657-663.
Youle, R. J., & Van Der Bliek, A. M. (2012). Mitochondrial fission, fusion, and stress. Science, 337(6098), 1062-1065.
Yu, T., Jhun, B. S., & Yoon, Y. (2011). High-glucose stimulation increases reactive oxygen species production through the calcium and mitogen-activated protein kinase-mediated activation of mitochondrial fission. Antioxidants & Redox Signaling, 14(3), 425-437.
Yu, X., Jia, L., Yu, W., & Du, H. (2019). Dephosphorylation by calcineurin regulates translocation of dynamin-related protein 1 to mitochondria in hepatic ischemia reperfusion induced hippocampus injury in young mice. Brain Research, 1711, 68-76.
Zhang, F., Vierock, J., Yizhar, O., Fenno, L. E., Tsunoda, S., Kianianmomeni, A., & Magnuson, J. (2011). The microbial opsin family of optogenetic tools. Cell, 147(7), 1446-1457.
Zunino, R., Braschi, E., Xu, L., & McBride, H. M. (2009). Translocation of SenP5 from the nucleoli to the mitochondria modulates DRP1-dependent fission during mitosis. Journal of Biological Chemistry, 284(26), 17783-17795.