The endothelial E3 ligase HECW2 promotes endothelial cell junctions by increasing AMOTL1 protein stability via K63-linked ubiquitination

Cell-to-cell junctions are critical for the formation of endothelial barriers, and its disorganization is required for sprouting angiogenesis. Members of the angiomotin (AMOT) family have emerged as key regulators in the control of endothelial cell (EC) junction stability and permeability. However, the underlying mechanism by which the AMOT family is regulated in ECs remains unclear. Here we report that HECW2, a novel EC ubiquitin E3 ligase, plays a critical role in stabilizing endothelial cell-to-cell junctions by regulating AMOT-like 1 (AMOTL1) stability. HECW2 physically interacts with AMOTL1 and enhances its stability via lysine 63-linked ubiquitination. HECW2 depletion in human ECs decreases AMOTL1 stability, loosening the cell-to-cell junctions and altering subcellular localization of yes-associated protein (YAP) from cytoplasm into the nucleus. Knockdown of HECW2 also results in increased angiogenic sprouting, and this effect is blocked by depletion of ANG-2, a potential target of YAP. These results demonstrate that HECW2 is a novel regulator of angiogenesis and provide new insights into the mechanisms coordinating junction stability and angiogenic activation in ECs.ope

Direct endothelial junction restoration results in significant tumor vascular normalization and metastasis inhibition in mice.

Tumor blood vessels are leaky and immature, which causes inadequate blood supply to tumor tissues resulting in hypoxic microenvironment and promotes metastasis. Here we have explored tumor vessel modulating activity of Sac-1004, a recently developed molecule in our lab, which directly potentiates VE-cadherin-mediated endothelial cell junction. Sac-1004 could enhance vascular junction integrity in tumor vessels and thereby inhibit vascular leakage and enhance vascular perfusion. Improved perfusion enabled Sac-1004 to have synergistic anti-tumor effect on cisplatin-mediated apoptosis of tumor cells. Interestingly, characteristics of normalized blood vessels namely reduced hypoxia, improved pericyte coverage and decreased basement membrane thickness were readily observed in tumors treated with Sac-1004. Remarkably, Sac-1004 was also able to inhibit lung and lymph node metastasis in MMTV and B16BL6 tumor models. This was in correlation with a reduction in epithelial-to-mesenchymal transition of tumor cells with considerable diminution in expression of related transcription factors. Moreover, cancer stem cell population dropped substantially in Sac-1004 treated tumor tissues. Taken together, our results showed that direct restoration of vascular junction could be a significant strategy to induce normalization of tumor blood vessels and reduce metastasis.ope

Roles of YAP in mediating endothelial cell junctional stability and vascular remodeling

Angiogenesis is a complex process involving dynamic interaction of various cell to cell interactions. Endothelial cell interactions regulated by growth factors, inflammatory cytokines, or hemodynamic stress are critical for balancing vascular quiescence and activation. Yes-associated protein (YAP), an effector of Hippo signaling, is known to play significant roles in maintaining cellular homeostasis. However, its role in endothelial cells for angiogenic regulation remains relatively unexplored. We demonstrated the critical role of YAP in vascular endothelial cells and elucidated the underlying molecular mechanisms involved in angiogenic regulation of YAP. YAP was expressed in active angiogenic regions where endothelial cell junctions were relatively loosened. Consistently, YAP subcellular localization and activity were regulated by VE-cadherin-mediated PI3K/Akt pathway. YAP thereby regulated endothelial sprouting via angiopoietin-2 expression. These results provide an insight into a model of coordinating endothelial junctional stability and angiogenic activation through YAP.ope

LDB2 regulates the expression of DLL4 through the formation of oligomeric complexes in endothelial cells

Delta-like ligand 4 (DLL4) expression in endothelial cells is intimately associated with angiogenic sprouting and vascular remodeling, but the precise mechanism of transcriptional regulation of DLL4 remains incompletely understood. Here, we showed that LIM-domain binding protein 2 (LDB2) plays an important role in regulating basal DLL4 and VEGF-induced DLL4 expression. Knockdown of LDB2 using siRNA enhanced endothelial sprouting and tubular network formation in vitro. Injection of ldb2-morpholino resulted in defective development of intersegmental vessels in zebrafish. Reduction or overexpression of LDB2 in endothelial cells decreased or increased DLL4 expression. LDB2 regulated DLL4 promoter activity by binding to its promoter region and the same promoter region was occupied and regulated by the LMO2/TAL1/GATA2 complex. Interestingly, LDB2 also mediated VEGF-induced DLL4 expression in endothelial cells. The regulation of DLL4 by the LDB2 complex provides a novel mechanism of DLL4 transcriptional control that may be exploited to develop therapeutics for aberrant vascular remodeling.ope

Increased Thrombogenicity in Chronic Renal Failure in a Rat Model Induced by 5/6 Ablation/Infarction.

PURPOSE: Abnormalities in hemostasis and coagulation have been suggested in chronic renal failure (CRF). In this study, we compared processes of thrombus formation between rats with CRF and those with normal kidney function. MATERIALS AND METHODS: CRF was induced by 5/6 ablation/infarction of the kidneys in Sprague-Dawley rats, and surviving rats after 4 weeks were used. Ferric chloride (FeCl₃)-induced thrombosis in the carotid artery was induced to assess thrombus formation. Whole blood clot formation was evaluated using rotational thromboelastometry (ROTEM). Platelet aggregation was assessed with impedance platelet aggregometry. RESULTS: FeCl₃-induced thrombus formation was initiated faster in the CRF group than in the control group (13.2±1.1 sec vs. 17.8±1.0 sec, p=0.027). On histological examination, the maximal diameters of thrombi were larger in the CRF group than in the control group (394.2±201.1 μm vs. 114.0±145.1 μm, p=0.039). In extrinsic pathway ROTEM, the CRF group showed faster clot initiation (clotting time, 59.0±7.3 sec vs. 72.8±5.0 sec, p=0.032) and increased clot growth kinetics (α angle, 84.8±0.2° vs. 82.0±0.6°, p=0.008), compared to the control group. Maximal platelet aggregation rate was higher in the CRF group than in the control group (58.2±0.2% vs. 44.6±1.2%, p=0.006). CONCLUSION: Our study demonstrated that thrombogenicity is increased in rats with CRF. An activated extrinsic coagulation pathway may play an important role in increasing thrombogenicity in CRF.ope

TNF-α-Induced YAP/TAZ Activity Mediates Leukocyte-Endothelial Adhesion by Regulating VCAM1 Expression in Endothelial Cells

YAP/TAZ, a transcriptional co-activator of Hippo pathway, has emerged as a central player in vessel homeostasis such as sprouting angiogenesis and vascular barrier stabilization, during development. However, the role of YAP/TAZ in pathological angiogenesis remains unclear. Here, we demonstrated that YAP/TAZ is a critical mediator in leukocyte-endothelial adhesion induced by the vascular inflammatory cytokine TNF-α. YAP/TAZ was dephosphorylated, translocated from the cytosol to the nucleus, and activated by TNF-α in endothelial cells. A specific inhibitor of Rho GTPases suppressed the TNF-α-induced dephosphorylation of YAP. Knockdown of YAP/TAZ using siRNA significantly reduced the expression of the leukocyte adhesion molecule VCAM1 induced by TNF-α. The adhesion of monocytes to endothelial cells was also markedly reduced by YAP/TAZ silencing. However, knockdown of YAP/TAZ did not affect TNF-α-induced NF-κB signaling. Overall, these results suggest that YAP/TAZ plays critical roles in regulating TNF-α-induced endothelial cell adhesive properties without affecting the NF-κB pathway, and implicate YAP/TAZ as a potential therapeutic target for treating inflammatory vascular diseases.ope

Focusing on the Russian perspective

학위논문 (석사)-- 서울대학교 대학원 : 국제대학원 국제학과(국제협력전공), 2019. 2. 신성호.중국과 러시아의 관계는 협력과 경쟁이 항상 존재해왔다. 러시아는 최근 아시아로 눈을 돌리면서 신동방정책과 함께 극동지역에서의 정치적, 경제적 입지를 강화하고 있다. 이에 따라 중국과의 관계는 발전될 거라 예상하였지만 실질적인 협력의 진전이 보이지 않고 있다. 본 논문은 이를 러시아 극동지역(지역차원)과 자루비노 항만 개발프로젝트(소지역 차원)로 구분하여 두 국가간 협력이 지체되는 원인을 러시아의 입장에서 분석하였다. 우선 지역차원의 극동지역에서 러시아가 중국과 대치의 이유로는 1) 중국을 이용한 미국의 아시아 회귀정책(Pivot to Asia)에 대한 견제와 이에 따른 자국의 강대국 입지 재확보와 2) 아시아 태평양 지역에서의 중국 부상 우려가 있다. 소지역 차원의 자루비노 항만 개발에서 러시아는 1) 접경지역에서의 중국 우세 우려와 2) 이 지역개발에 대한 낮은 수준의 책임감에 있다. 극동지역에서 러시아는 국제시스템의 미국에 대한 견제와 균형, 지역적 수준에서의 중국에 대한 위험분산(hedging)의 두 가지 단계가 관찰되어진다. 지역적 및 소지역적 차원에서 러시아는 중국과의 관계에 있어 경제적인 측면보다는 자국의 안보를 더 중시하고 있다. 그 결과 현재 러시아는 다른 주요 동아시아 국가들의 참여를 유도하는 등 투자의 다양화를 하는 노력을 하고 있다. 한국은 극동지역에서의 개발참여를 통해 동아시아에 대한 영향력을 강화하고 추후에 북한과 러시아간 3국 경제협력에 동참할 수 있는 기회가 있기 때문에 적극적으로 개발참여를 모색할 필요가 있다.Cooperation and Competition simultaneously existed in the Sino-Russian relations. As Russia turned its attention to Asia and prioritized the Turn to the East policy and tried to increase its political influence and economic presence in the Russian Far East (RFE), Sino-Russian economic relations were expected to develop. However, cooperation was not showing much progress. This paper analyzed the hindrance factors from the Russian perspective by dividing in to two approaches: RFE (Regional level) and Zarubino Port Development project (Sub-regional level). In the RFE, the main hindrance factors were 1) Balancing US pivot to Asia and resurging their status of super power, 2) Wary of China's emergence in the Asia Pacific region. In the Sino-Russian border areas, the hindrance factors were 1) Wary of China's domination in the Sino- Russian border areas, 2) Low commitment to develop the border areas. In the China-Russia relations, we can observe two levels: Balancing against US on the international system and hedging to one another to its regional level. Both regional and sub-regional level approach show Russia is more concerned to security rather than economic cooperation when dealing with China in the RFE. Accordingly, Russia is trying to diversify its source of investment by inviting other main North East Asian (NEA) countries. For Korea, this is an opportunity to improve its influence in NEA and later attract North Korea(NK) to participate in the trilateral economic cooperation between two Koreas and Russia. Therefore, it is important to consider participating the RFE development, if conditions allow.I. Introduction 1 1. Research Purpose and Significance 2 2. Research Design 4 2-1. Literature Review 4 2-2. Research Question 8 2-3. Research Outline 9 II. China- Russia Relationship in the Russian Far East (RFE) 11 1. Strategic Value and Regional Development of Russia Far East 11 2. Strategic Partnership between China and Russia 18 3. China- Russia Interactions in the RFE 21 3-1. Hindrance Factors 25 3-1-1. Balancing US pivot to Asia 25 3-1-2. Wary of China's emergence in the Asia Pacific region 27 4. Assessment of Russias position in RFE 30 III. Cross-border cooperation in the Russian Far East (RFE) 31 1. Construction of transport network in the Sino-Russian border areas 31 2. China - Russia interactions in the Sino- Russian border areas 32 3. Sino - Russian cooperative project: Zarubino Port Development Project 37 3-1. Hindrance Factors 43 3-1-1. Wary of China's dominance in the Sino - Russian border areas 43 3-1-2. Low Commitment to develop the border areas 46 4. Assessment of Russias position in border areas 47 IV. Implications for Korea and the Regional cooperation in NEA 49 1. Regional cooperation in North East Asia 49 2. Implication for Korea 52 V. Conclusion 55 VI. Reference 59 VII. Abstract in Korean 77Maste

EJC에서의 Aly의 역할과 Y14과의 상호작용에 관한 연구

학위논문(석사)--서울대학교 대학원 :협동과정 유전공학전공,2003.Maste

한국 청소년의 식품 및 영양소 섭취실태가 골밀도에 미치는 영향

학위논문(석사)--서울대학교 보건대학원 :보건학과 보건영양전공,2006.Maste