HIPPO Signaling in Pulmonary Arterial Hypertension

肺动脉高压（PAH）是一种进行性致死性疾病，表现为肺动脉重构， 动脉粥样硬化（PA），导致PA压力增加，右心衰竭和死亡。PA重塑的关键组成部分 PA血管平滑肌细胞（PAVSMC）的增殖和存活增加与过量的 细胞外基质（ECM）的产生。我们最近发现了LATS 1的功能障碍，LATS 1是生长因子的一个成员， 抑制HIPPO盒，作为支持增殖性/抗增殖性PAH PAVSMC表型的关键事件， 型，通过上调雅普/Taz-ILK 1，剖析了LATS 1失活的机制，并证明了本- ILK 1抑制对恢复LATS 1功能、逆转肺血管重构和降低PH的作用。 其他HIPPO组分、蛋白激酶MST 1/2在PAH中的作用仍有待确定。我们发现 MST 1/2在PAH中发挥独特促增殖/促存活作用，并支持增殖和存活增加， 小鼠肺动脉高压、肺血管平滑肌细胞存活、肺血管重构和肺动脉高压。我们报告说， MST 1/2依赖于Akt和独特的PAH特异性与细胞周期蛋白BUB 3的相互作用。此外，我们表明， MST 1/2和BUB 3通过支持细胞分裂周期蛋白CDC 20的过表达而起作用， 促凋亡Bim，Akt、mTORC 1和雅普/Taz的激活，增殖、存活和过度促凋亡Bim的增加， ECM的引入。反过来，由人PAH PAVSMC产生的ECM上调BUB 3、Akt-mTORC 1、雅普/Taz， 和PAVSMC增殖，并诱导PA内皮细胞（PAEC）和外膜成纤维细胞的生长 （PAAF）。最后，我们的数据表明，药物抑制MST 1/2逆转PAH特异性信号传导异常， 恶性并选择性抑制人PAH PAVSMC的增殖和/或促进凋亡，而不影响 非病变细胞。在下一个拨款期内，我们建议阐明监管的角色、机制， MST 1/2在PAH中的功能，并探索靶向MST 1/2信号传导以纠正机制异常的益处。 具体而言，我们将：（1）严格评估MST 1和2的作用， 相互作用伴侣BUB 3和下游效应物CDC 20在调节Akt、mTORC 1和雅普/Taz网络中的作用， PAVSMC增殖和存活、肺血管重塑和PH使用人PAH和非病变 组织和PAVSMC以及VSM特异性Mst 1/2敲除小鼠;（2）确定病理功能是否 PAH PAVSMC中的MST 1/2由Akt直接或通过Akt-BUB 3-雅普/Taz前馈环路支持，并评估 MST 1/2在PAEC和PAAF的ECM重塑和ECM依赖性增殖中的作用;和（3）测试po- 通过药理学抑制MST 1/2激酶、Akt或（alterna-Akt）来靶向MST 1/2信号传导的潜在益处 目的）CDC 20选择性抑制增殖、诱导凋亡和减少病理性ECM产生 通过人PAH PAVSMC，减少随后的PAEC和PAAF的过度增殖，并逆转实验性 肺血管重构和PH。拟议的研究将确定一个新的关键机制， 血管重塑和解剖新的重塑聚焦分子靶点用于治疗干预。 .

Pulmonary arterial hypertension (PAH), a progressive fatal disease, manifests by remodeling of pulmonary ar- teries (PA), leading to increased PA pressure, right heart failure and death. Key components of PA remodeling are increased proliferation and survival of PA vascular smooth muscle cells (PAVSMC) associated with exces- sive extracellular matrix (ECM) production. We recently identified dysfunction of LATS1, a member of growth- suppressor HIPPO cassette, as a key event supporting proliferative/apoptosis-resistant PAH PAVSMC pheno- type, dissected the mechanism of LATS1 inactivation via up-regulation of Yap/Taz-ILK1, and demonstrated ben- efits of ILK1 inhibition to restore LATS1 function, reverse pulmonary vascular remodeling and reduce PH. The role of other HIPPO components, protein kinases MST1/2, in PAH remains to be established. We have found that MST1/2 in PAH play a unique pro-proliferative/pro-survival role and support increased proliferation and sur- vival of human PAH PAVSMC, pulmonary vascular remodeling and PH in mice. We report that this function of MST1/2 depend on Akt and unique PAH-specific interaction with cell cycle protein BUB3. Further, we show that MST1/2 and BUB3 act via supporting overexpression of cell-division cycle protein CDC20, consequent deficiency of pro-apoptotic Bim, activation of Akt, mTORC1, and Yap/Taz, increased proliferation, survival, and over-pro- duction of ECM. In turn, ECM, produced by human PAH PAVSMC, up-regulates BUB3, Akt-mTORC1, Yap/Taz, and PAVSMC proliferation, and induces growth of PA endothelial cells (PAEC) and adventitial fibroblasts (PAAF). Lastly, our data show that pharmacological inhibition of MST1/2 reverses PAH-specific signaling abnor- malities and selectively inhibits proliferation and/or promotes apoptosis in human PAH PAVSMC without affecting non-diseased cells. During the next funding period, we propose to elucidate roles, mechanisms of regulation and function of MST1/2 in PAH, and explore the benefits of targeting MST1/2 signaling to correct mechanistic abnor- malities and reverse PA remodeling and PH. Specifically, we will: (1) critically evaluate roles of MST1 and 2, its interacting partner BUB3 and downstream effector CDC20 in regulating Akt, mTORC1 and Yap/Taz networks, PAVSMC proliferation and survival, pulmonary vascular remodeling and PH using human PAH and non-diseased tissues and PAVSMC and mice with VSM-specific Mst1/2 knockout; (2) determine whether pathological function of MST1/2 in PAH PAVSMC is supported by Akt directly or via Akt-BUB3-Yap/Taz fed-forward loop, and evaluate the role of MST1/2 in ECM remodeling and ECM-dependent proliferation of PAEC and PAAF; and (3) test po- tential benefits of targeting MST1/2 signaling by pharmacological inhibition of MST1/2 kinase, Akt, or (alterna- tively) CDC20 to selectively suppress proliferation, induce apoptosis and reduce pathological ECM production by human PAH PAVSMC, reduce consequent hyper-proliferation of PAEC and PAAF, and reverse experimental pulmonary vascular remodeling and PH. The proposed study will identify a new critical mechanism of pulmonary vascular remodeling and dissect new remodeling-focused molecular target(s) for therapeutic intervention. .