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SIRT3 deregulation is linked to mitochondrial dysfunction in Alzheimer's disease
Lee, Junghee,Kim, Yunha,Liu, Tian,Hwang, Yu Jin,Hyeon, Seung Jae,Im, Hyeonjoo,Lee, Kyungeun,Alvarez, Victor E.,McKee, Ann C.,Um, Soo‐,Jong,Hur, Manwook,Mook‐,Jung, Inhee,Kowall, Neil W.,Ry John Wiley and Sons Inc. 2018 Aging cell Vol.17 No.1
<P><B>Summary</B></P><P>Alzheimer's disease (AD) is the leading cause of dementia in the elderly. Despite decades of study, effective treatments for AD are lacking. Mitochondrial dysfunction has been closely linked to the pathogenesis of AD, but the relationship between mitochondrial pathology and neuronal damage is poorly understood. Sirtuins (SIRT, silent mating type information regulation 2 homolog in yeast) are NAD‐dependent histone deacetylases involved in aging and longevity. The objective of this study was to investigate the relationship between SIRT3 and mitochondrial function and neuronal activity in AD. SIRT3 mRNA and protein levels were significantly decreased in AD cerebral cortex, and Ac‐p53 K320 was significantly increased in AD mitochondria. SIRT3 prevented p53‐induced mitochondrial dysfunction and neuronal damage in a deacetylase activity‐dependent manner. Notably, mitochondrially targeted p53 (mito‐p53) directly reduced mitochondria DNA‐encoded ND2 and ND4 gene expression resulting in increased reactive oxygen species (ROS) and reduced mitochondrial oxygen consumption. ND2 and ND4 gene expressions were significantly decreased in patients with AD. p53‐ChIP analysis verified the presence of p53‐binding elements in the human mitochondrial genome and increased p53 occupancy of mitochondrial DNA in AD. SIRT3 overexpression restored the expression of ND2 and ND4 and improved mitochondrial oxygen consumption by repressing mito‐p53 activity. Our results indicate that SIRT3 dysfunction leads to p53‐mediated mitochondrial and neuronal damage in AD. Therapeutic modulation of SIRT3 activity may ameliorate mitochondrial pathology and neurodegeneration in AD.</P>
김도헌(Dohun Kim),박재현(Jaehyeon Park),유명곤(Myunggon Yu),이경은(Kyungeun Lee),구자예(Jaye Koo) 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12
아산화질소/에탄올 추진제 조합을 사용하는 50N급 추력기의 shadowgraphy 기법을 사용한 분사기 인접 영역에서의 연소 유동장 가시화가 수행되었다. 설계 작동조건에서 폭발성 점화가 일어났으며, 급격히 팽창하는 연소가스에 의해 순간적으로 소염되었다. 최초 점화로부터 약 83 ms 뒤 추진제 분무는 재점화 되었으며, 그로부터 약 23 ms 후 화염이 안정화되는 것이 관찰되었다. 동일한 시퀀스에서 설계 조건보다 산화제 유량을 증가시킨 경우 소염 현상 없이 완만한 연소 압력 과도 특성을 보였으며, 약 17 ms의 빠른 화염 안정화가 이루어져다. 점화 직전의 연소기 내부 미연 추진제 혼합 향상에 의한 것으로 생각되었다. The combustion flowfield at the near-injector region of a 50N scale N2O/C2H5OH thruster was visualized using shadowgraphy technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.
Yang, Seo-Yun,Lee, Jae-Jin,Lee, Jin-Hee,Lee, Kyungeun,Oh, Seung ,Hoon,Lim, Yu-Mi,Lee, Myung-Shik,Lee, Kong-Joo Portland Press Ltd. 2016 Biochemical journal Vol.473 No.12
<P>Secretagogin (SCGN), a Ca2+-binding protein having six EF-hands, is selectively expressed in pancreatic beta-cells and neuroendocrine cells. Previous studies suggested that SCGN enhances insulin secretion by functioning as a Ca2+-sensor protein, but the underlying mechanism has not been elucidated. The present study explored the mechanism by which SCGN enhances glucose-induced insulin secretion in NIT-1 insulinoma cells. To determine whether SCGN influences the first or second phase of insulin secretion, we examined how SCGN affects the kinetics of insulin secretion in NIT-1 cells. We found that silencing SCGN suppressed the second phase of insulin secretion induced by glucose and H2O2, but not the first phase induced by KCl stimulation. Recruitment of insulin granules in the second phase of insulin secretion was significantly impaired by knocking down SCGN in NIT-1 cells. In addition, we found that SCGN interacts with the actin cytoskeleton in the plasma membrane and regulates actin remodelling in a glucose-dependent manner. Since actin dynamics are known to regulate focal adhesion, a critical step in the second phase of insulin secretion, we examined the effect of silencing SCGN on focal adhesion molecules, including FAK (focal adhesion kinase) and paxillin, and the cell survival molecules ERK1/2 (extracellular-signal-regulated kinase 1/2) and Akt. We found that glucose-and H2O2-induced activation of FAK, paxillin, ERK1/2 and Akt was significantly blocked by silencing SCGN. We conclude that SCGN controls glucose-stimulated insulin secretion and thus may be useful in the therapy of Type 2 diabetes.</P>
50 N급 아산화질소/에탄올 추력기의 점화 과도 유동장 가시화
김도헌(Dohun Kim),박재현(Jaehyeon Park),유명곤(Myunggon Yu),이경은(Kyungeun Lee),구자예(Jaye Koo) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.6
The combustion flowfield at the near-injector region of a 50 N scale N₂O/C₂H?OH thruster was visualized using shadowgraph technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.