PECAM-1在机械信号转导的作用
The Function of Platelet Endothelial Cell Ad-hesion Molecule-1 (PECAM-1) in Mechanotransduction
DOI: 10.12677/PI.2018.72005, PDF, HTML, XML, 下载: 1,383  浏览: 3,006 
作者: 李胜存, 韩吉春, 尚 靖*：中国药科大学中药学院，江苏 南京
关键词: PECAM-1；机械敏感受体；机械信号转导；PECAM-1； Mechanoreceptors； Mechanotransduction
摘要: 动脉粥样硬化(Atherosclerosis, As)是一种慢性炎症性疾病，好发于血管分支、分叉及弯曲内侧这些血流紊乱部位。局部因素如血流动力学在动脉粥样硬化好发局部位置过程中起重要作用。内皮细胞表面有很多可以感受力刺激的机械敏感受体，机械敏感受体一旦活化会激活细胞内数条信号通路，引起某些转运因子发生磷酸化，与机械敏感响应原件结合调控机械敏感基因的表达，调节细胞功能变化。本文就机械敏感受体PECAM-1在机械信号转导中的作用进行综述。
Abstract: Atherosclerosis is a chronic, inflammatory disease form at specific regions of the arterial tree such as in the vicinity of branch points, the outer wall of bifurcations, and the inner wall of curvatures, where disturbed flow occurs. Local factors, such as hemodynamic forces, play a major role in the re-gional localization of atherosclerosis. Endothelial cell (EC) surfaces are equipped with numerous mechanoreceptors capable of detecting and responding to forces stimuli. After activation of mecha-noreceptors, a complex network of several intracellular pathways is triggered. These pathways lead to phosphorylation of several transcription factors (TFs), which bind positive or negative shear stress responsive elements (SSREs) at promoters of mechanosensitive genes, ultimately, modulat-ing cellular function and morphology. Here, we focus on the function of platelet endothelial cell ad-hesion molecule-1 (PECAM-1), one of the mechanoreceptors, in mechanotransduction.
文章引用：李胜存, 韩吉春, 尚靖. PECAM-1在机械信号转导的作用[J]. 药物资讯, 2018, 7(2): 21-26. https://doi.org/10.12677/PI.2018.72005

1. 引言

动脉粥样硬化(Atherosclerosis, As)是一种发生在大中型动脉的慢性、炎症性的纤维增厚性疾病。尽管整个血管暴露在致动脉粥样硬化的系统性危险因素中(如高脂血症，吸烟、高血压、糖尿病、慢性感染和遗传倾向)，但As病变主要发生在血管分支点附件、分岔外壁、弯曲血管的内壁这些血流紊乱的区域。局部因素如血流动力学在As发生局灶性中起主要作用 [1] 。

从动脉粥样硬化的病灶选择性入手，通过研究病灶性部位的血流动力学，人们发现动脉粥样硬化病变位置与动脉内血液的流动低速区、回流区相关，而这些区域所共有的血流动力学特点，就是低的壁面剪应力(LSS) (0~4 dyne/cm2)或交变的壁面剪应力 [2] 。目前普遍认为，低剪应力和长的粒子(如血脂质)滞留时间才是动脉疾病最危险的血流动力学因素 [3] 。低剪切力可以诱导内皮细胞功能紊乱，致动脉粥样硬化因子分泌增多而抗动脉粥样硬化因子分泌减少，促进动脉粥样硬化发生和进展。

内皮细胞(EC)的表面存在着许多可以感受和响应内皮剪切力刺激了的机械敏感受体，如血小板内皮细胞粘附分子-1 (platelet endothelial cell adhesion molecule-1, PECAM-1)、整合素家族、受体酪氨酸激酶、G蛋白及G蛋白偶联受体、离子通道等 [4] [5] [6] 。机械敏感受体活化后会激活细胞内数条信号通路 [4] [5] [7] [8] [9] [10] 。这些通路可同时被激活并进行信号转导，进而引发一系列生物学效应。本文重点阐述机械敏感受体PECAM-1在血流剪切力机械信号感受、传导及其调控的相关生物学功能。

2. PECAM-1

PECAM-1是细胞粘附分子中的免疫球蛋白超家族成员，分子量130 KD，主要在人粒细胞，单核细胞，血小板和血管内皮细胞的表面上表达 [11] ，参与多种生物学功能如血小板活化，信号转导，白细向内皮细胞迁移及炎症反应。PECAM-1胞内区有两个免疫受体酪氨酸抑制基序(immunoreceptor tyrosine-based inhibitory motif (ITIM))。PECAM-1第663位酪氨酸和第686位酪氨酸被磷酸化后，募集含Src同源域蛋白(Src homology 2)与其结合，主要是含SH2酪氨酸磷酸酶(SH2 domain-containing protein tyrosine phosphatase, SHP-2)。可与PECAM-1磷酸化ITIMs相结合的含Src同源域蛋白主要有Src家族激酶(Src family kinase, SFK)，SHP-1，磷脂酶Cγ (Phospholipase Cγ, PLCγ)等 [6] [12] 。

3. PECAM-1参与血流剪切力信号感受

PECAM-1作为机械敏感受体，其活性受机械信号调节。内皮细胞在施加剪切力后PECAM-1会发生迅速磷酸化 [13] [14] ，随即即可诱导酪氨酸磷酸酶SHP-2向内皮细胞间连接处聚集，引起下游信号通路的活化。研究发现PECAM-1、血管内皮细胞钙粘素(Vascular endothelialcell cadherin, VE-cadherin)和血管内皮生长因子受体2 (Vascular endothelial growth factor receptor 2, VEGFR2)参与形成机械敏感复合物，参与机械力的感受和传导。其中PECAM-1直接感受机械力刺激，VE-cadherin起衔接蛋白作用，VEGFR2起活化磷酸酰肌醇3-OH (Phosphatidylinositol-3-OH kinase, PI3K)作用 [6] 。

4. PECAM-1介导的血流剪切力信号转导

4.1. PECAM-1/SHP-2/Gab1

研究表明SHP2，Gab1，蛋白激酶A (Protein Kinase A, PKA)参与血流剪切了诱导的NO合酶的活化 [15] ，血流剪切力可以促进SHP2、Gab1酪氨酸磷酸化及Akt、eNOS活化。Gab1突变可抑制血流剪切力诱导的Akt的磷酸化，Gab1 Tyr627 (YF-Gab1)突变抑制Gab1与SHP2结合及血流剪切力诱导的eNOS的磷酸化。而siRNA沉默PECAM-1可抑制血流剪切力诱导的Gab1的酪氨酸磷酸化和膜转移以及Akt和eNOS的活化，同样在PECAM-1-/-小鼠中发现剪切力诱导的Gab1及eNOS磷酸化降低 [16] 。这些结果表明PECAM-1在血流诱导的Gab1磷酸化及信号转导起重要作用(图1)。

4.2. PECAM-1/SHP-2/ERK

细胞外信号调节激酶1/2 (extracellular signal-regulated kinase-1/2, ERK1/2)在剪切力诱导的内皮细胞功能紊乱中起重要作用。王志梅 [17] 研究发现低剪切力可以通过ERK/eNOS信号通路引起内皮细胞氧化应激，低剪切力促进ERK和eNOSThr495位点磷酸化，给予ERK抑制剂PD98059可以抑制低剪切力诱导的eNOSThr495的磷酸化，增加SOD活性。有研究表明血流剪切力诱导的内皮细胞ERK1/2及eNOS的活化需要PECAM-1的参与 [18] ，HUVECs或BAECs给予剪切力10分钟后ERK1/2、eNOS发生显著磷酸化，siRNA沉默PECAM-1可抑制血流剪切力诱导ERK1/2、eNOS的磷酸化。表明PECAM-1参与调节机械信号向ERK1/2的转导(图1)。

4.3. PECAM-1/PI3K/Akt

已在多种类型的细胞中发现Phosphatidylinositol-3-OH kinase (PI(3)K)参与整合素的活化 [19] 。在内皮细胞中，给予血流刺激15 s后就发现PI(3)K亚基p85发生磷酸化，并在后续时间持续增强。剪切力诱导的PI3K的活化需要PECAM-1、VE-cadherin及c-Src的参与，剪切力在数秒内即可活化c-Src [6] 。研究表明在给予血流15 s时Src激活达到最大水平，略微快于PI(3)K的磷酸化，Src抑制剂PP2或SU6656可抑制血流诱导的PI(3)K p85亚基和整合素αvβ5的活化 [7] 。因此Src家族激酶是剪切力诱导的PI(3)K依赖的整合素活化的上游。VE-cadherin-/-内皮细胞给予剪切力后PI(3)K磷酸化及AKT磷酸化并未增加，Src的活化虽然延迟并没有被抑制。然而PECAM-1-/-内皮细胞给予剪切力后PI(3)K、AKT及Src都未见活化 [6] 。因此Src的活化需要PECAM-1参与，而VE-cadherin参与PECAM-1信号向PI(3)K/Akt的传递(图1)。

4.4. PECAM-1/αvβ3/Ras

整合素家族粘附分子(integrins)整合素家族粘附分子是由α和β亚单位组成的二聚体糖蛋白，主要介

Figure 1. The mechanotransduction of shear stress induced by PECAM-1

图1. PECAM-1介导的血流剪切力信号转导

导细胞与细胞外基质(extra celluar matrix, ECM)的相互作用，在细胞粘附、细胞迁移、细胞生长分化和炎症中发挥着重要作用 [20] 。整合素家族作为内皮细胞重要的机械敏感受体介导机械信号有细胞外向细胞内的转导 [21] ，例如αvβ3是血管内皮细胞中重要的整合素分子，血流剪切力能引起它与接头分子(adaptor) Shc的结合，进一步通过Shc-Grb2-Sos激活Ras蛋白，上调ERK和JNK的活性，而抗αvβ3的特异性抗体能阻断血流剪切力对ERK和JNK的活化 [22] 。研究发现剪切力诱导的αvβ3的活化受PECAM-1的调节 [6] ，PECAM-1-/-内皮细胞给予剪切力后整合素αvβ3并未被激活，表明PECAM-1可能作为αvβ3上游信号分子参与剪切力诱导的αvβ3的活化(图1)。

5. PECAM-1介导的血流剪切力诱导的生物学效应

5.1. PECAM-1参与剪切力诱导的细胞骨架重排

机械力如血流剪切力直接作用于血管内皮细胞，调控血管内皮细胞的病理生理功能。在血管层流区域，血管内皮细胞延血流方向紧密排列，而在紊流及低剪切力区域(血管弯曲及分叉处)血管内皮细胞呈多边形或鹅卵石样排列 [23] [24] 。整合素在剪切力诱导的机械信号转导细胞骨架重排中起重要作用 [7] ，整合素的胞内域可与α-辅肌动蛋白(α-acttin)、纽蛋白(vinculin)、踝蛋白(talin)、张力蛋白(tensin)等细胞骨架蛋白连接，通过这些骨架蛋白最终连结到肌动蛋白(actin)上，引起细胞的形态变化。血流剪切了可以迅速活化αvβ3，进而通过Rho参与的细胞骨架重排。PECAM-1-/-内皮细胞给予剪切力后未见细胞骨架延剪切力方向重排，裸细胞重组PECAM-1给予剪切力后细胞骨架发生重排 [6] 。

5.2. PECAM-1参与剪切力诱导的内皮细胞炎症反应

炎症反应在动脉粥样硬化的发生发展中起重要作用，多种病理刺激都可以诱导内皮细胞细胞间粘附分子(ICAM)、血管细胞粘附分子(VCAM)及选择素(如P选择素和E选择素)表达增加，促进单核细胞向内皮细胞的粘附、浸润 [25] 。NF-κB是炎症过程中的关键调控因子，NF-κB被激活后向细胞核迁移进而促进炎症相关基因的表达，诱导炎症反应。体内研究表明 [6] ，与层流剪切力处血管相比，野生型小鼠主动脉分叉处NF-κB核转移明显增加，ICAM-1表达增多。而PECAM-1-/-小鼠血管分叉处并未发现NF-κB的活化及ICAM-1的表达。体外研究发现 [26] ，低剪切力通过PECAM-1/PARP-1通路诱导内皮细胞炎症反应。低剪切力可以诱导HMGB1由细胞核向细胞质的转移及释放，增加PECMA-1和PARP-1的表达及TNF-α、IL-1β的分泌。抑制HMGB1可抑制低剪切力诱导的炎症反应，抑制PARP-1可以通过抑制TLR4的表达及HMGB1的迁移抑制炎症反应，PECAM-1沉默后降低低剪切力诱导的PARP-1、ICAM-1的表达及TNF-α和IL-1β的分泌。表明PECAM-1参与调节剪切力诱导的内皮细胞炎症反应。

6 总结和展望

当今动脉粥样硬化性心血管疾病仍是引起死亡的最主要原因，而临床上应用的抗动脉粥样硬化性心血管疾病的药物多为调脂药、抗炎氧化或抗血小板药物，但这些药物并不能从根本上逆转动脉粥样硬化斑块的存在。充分认知机械敏感受体在动脉粥样硬化斑块形成中的作用有助于人们在动脉粥样硬化斑块形成早期进行预防，对动脉粥样硬化性心血管疾病的防治中具有重要意义。

NOTES

*通讯作者。

参考文献

[1] Chatzizisis, Y.S. Coskun, A.U., et al. (2007) Role of Endothelial Shear Stress in the Natural History of Coronary Atherosclerosis and Vascular Remodeling. Journal of the American College of Cardiology, 49, 2379-2393.
https://doi.org/10.1016/j.jacc.2007.02.059
[2] Malek, A.M., Alper, S.L. and Izumo, S. (1999) Hemodynamic Shear Stress and Its Role in Atherosclerosis. JAMA, 282, 2035-2042.
https://doi.org/10.1001/jama.282.21.2035
[3] Taylor, C.A., Hughes, T.J.R. and Zarins, C.K. (1998) Finite Element Modeling of Bloodflow in Arteries. Computer Methods in Applied Mechanics and Engineering, 158, 156-196.
[4] Traub, O. and Berk, B.C. (1998) Laminar Shear Stress: Mechanisms by Which Endothelial Cells Transduce an Atheroprotective Force. Arteriosclerosis, Thrombosis, and Vascular Biology, 18, 677-685.
https://doi.org/10.1161/01.ATV.18.5.677
[5] Lehoux, S., Castier, Y. and Tedgui, A. (2006) Molecular Mechanisms of the Vas-cular Responses to Haemodynamic Forces. Journal of Internal Medicine, 259, 381-392.
https://doi.org/10.1111/j.1365-2796.2006.01624.x
[6] Tzima, E., Irani-Tehrani, M., Kiosses, W.B., et al. (2005) A Mecha-nosensory Complex That Mediates the Endothelial Cell Response to Fluid Shears Tress. Nature, 437, 426-431.
https://doi.org/10.1038/nature03952
[7] Tzima, E., del Pozo, M.A., Shattil, S.J., Chien, S. and Schwartz, M.A. (2001) Activa-tion of Integrins in Endothelial Cells by Fluid Shear Stress Mediates Rho-Dependent Cytoskeletal Alignment. The EMBO Journal, 20, 4639-4647.
https://doi.org/10.1093/emboj/20.17.4639
[8] Shyy, J.Y. and Chien, S. (2002) Role of Integrins in Endothelial Mechanosensing of Shear Stress. Circulation Research, 91, 769-775.
https://doi.org/10.1161/01.RES.0000038487.19924.18
[9] Lehoux, S. and Tedgui, A. (1998) Signal Transduction of Mechanical Stresses in the Vascular Wall. Hypertension, 32, 338-345.
https://doi.org/10.1161/01.HYP.32.2.338
[10] Davies, P.F., Barbee, K.A., Volin, M.V., et al. (1997) Spatial Relationships in Early Signaling Events of Flow-Mediated Endothelial Mechanotransduction. Annual Review of Physiology, 59, 527-549.
https://doi.org/10.1146/annurev.physiol.59.1.527
[11] Chistiakov, D.A., Orekhov, A.N. and Bobryshev, Y.V. (2016). Endotheli-al PECAM-1 and Its Function in Vascular Physiology and Atherogenic Pathology. Experimental and Molecular Pathology, 100, 409-415.
https://doi.org/10.1016/j.yexmp.2016.03.012
[12] .Paddock, C., Lytle, B.L., Peterson, F.C., Holyst, T., Newman, P.J., Volkman, B.F. and Newman, D.K. (2011) Residues within a Lipid-Associated Segment of the PECAM-1 Cytoplasmicdomain Are Susceptible to Inducible, Sequential Phosphorylation. Blood, 117, 6012-6023.
https://doi.org/10.1182/blood-2010-11-317867
[13] Harada, N., Masuda, M. and Fujiwara, K. (1995) Fluid Flow and Osmotic Stress Induce Tyrosine Phosphorylation of an Endothelial Cell 128 k Da Surface Glycoprotein. Biochemical and Biophysical Research Communications, 214, 69-74.
https://doi.org/10.1006/bbrc.1995.2257
[14] Osawa, M., Masuda, M., Harada, N., Lopes, R.B. and Fujiwara, K. (1997) Tyrosine Phosphorylation of Platelet Endothelial Cell Adhesionmolecule-1 (PECAM-1, CD31) in Mechanically Stimulated Vascularendothelial Cells. European Journal of Cell Biology, 72, 229-237.
[15] Dixit, M., Loot, A.E., Mohamed, A., Fisslthaler, B., Boulanger, C.M., Ceacareanu, B., Hassid, A., Busse, R. and Fleming, I. (2005) Gab1, SHP2, and Protein Kinase A Are Crucial for the Activation of the Endothelial NO Synthase by Fluid Shear Stress. Circulation Research, 97, 1236-1244.
https://doi.org/10.1161/01.RES.0000195611.59811.ab
[16] Xu, S., Ha, C.H., Wang, W., Xu, X., Yin, M., Jin, F.Q., Mastrangelo, M., Koroleva, M., Fujiwara, K. and Jin, Z.G. (2016) PECAM1 Regulates Flow-Mediated Gab1 Tyrosine Phosphorylation and Signal-ing. Cellular Signalling, 28, 117-124.
https://doi.org/10.1016/j.cellsig.2015.12.007
[17] Wang, Z.M., Zhang, J.X., Li, B., Gao, X.F., Liu, Y.R., Mao, W.X. and Chen, S.L. (2014) Resveratrol Ameliorates Low Shear Stress Induced Oxidative Stress by Suppress-ing ERK/eNOS? Thr495 in Endothelial Cells. Molecular Medicine Reports, 10, 1964-1972.
https://doi.org/10.3892/mmr.2014.2390
[18] Tai, L.K., Zheng, Q., Pan, S., Jin, Z.G. and Berk, B.C. (2005) Flow Activates ERK1/2 and Endothelial Nitric Oxide Synthase via a Pathway Involving PECAM1, SHP2, and Tie2. The Journal of Biological Chem-istry, 280, 29620-29624.
[19] Hughes, P.E. and Pfaff, M. (1998) Integrin Affinity Modulation. Trends in Cell Biology, 8, 359-364.
https://doi.org/10.1016/S0962-8924(98)01339-7
[20] Miranti, C.K. and Brugge, J.S. (2002) Sensing the Environment: A Histor-ical Perspective on Integrin Signal Transduction. Nature Cell Biology, 4, E83-E90.
https://doi.org/10.1038/ncb0402-e83
[21] Li, Y.S., Haga, J.H. and Chien, S. (2005) Molecular Basis of the Effects of Shear Stress on Vascular Endothelial Cells. Journal of Biome-chanics, 38, 1949-1971.
https://doi.org/10.1016/j.jbiomech.2004.09.030
[22] 唐植辉, 汪南平, 钱煦. 血流剪切力在动脉粥样硬化形成中的作用[J]. 生理科学进展, 2007(1): 37-42.
[23] Chiu, J.J. and Chien, S. (2011) Effects of Disturbed Flow on Vascular Endothelium: Pathophysiological Basis and Clinical Perspectives. Physiological Reviews, 91, 327-387.
https://doi.org/10.1152/physrev.00047.2009
[24] Davies, P.F., Civelek, M., Fang, Y. and Fleming, I. (2013) Theatherosuscepti-ble Endothelium: Endothelial Phenotypes in Complex Haemodynamic Shear Stress Regions in Vivo. Cardiovascular Research, 99, 315-327.
https://doi.org/10.1093/cvr/cvt101
[25] Ross, R. (1999) Atherosclerosis—An Inflammatory Disease. The New England Journal of Medicine, 340, 115-126.
[26] Qin, W., Mi, S. and Li, C. (2015) Low Shear Stress Induced HMGB1 Translocation and Release via PECAM-1/PARP-1 Pathway to Induce Inflammation Response. PLoS ONE, 10, e0120586.
https://doi.org/10.1371/journal.pone.0120586