报告题目：Mechanicalcuesaffects Ca2+signalingin stem cells

报 告  人：王英晓 Associate professor   Department of Bioengineering, University of California, San Diego

上海交通大学访问特聘教授

报告时间：7月8日 13:00

报告地点：闵行校区生物药学楼2-116

联 系  人：张萍 This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

个人简历

王英晓，博士，现任美国加州大学圣地亚哥分校生物工程系副教授，上海交通大学访问特聘教授。师从中国科学院外籍院士、美国国家科学院、国家工程院、国家医学科学院、国家艺术与科学学院院士ShuChien（钱煦）教授和诺贝尔奖获得者Roger Y. Tsien（钱永健）教授。从事力学生物学、生物技术、蛋白质工程和细胞分子力学生物学研究17年，在整合生物学前沿技术、新型分子传感器和荧光共振能量转移（FRET）技术发展和应用方面有很高的造诣，是一位年青有为的科学家。他在Nature、Nature Communications和PNAS等国际著名期刊发表论文50余篇，仅2008年在Ann Rev Biomed Eng发表的第1作者综述论文迄今已累计下载9353次，在国际学术会议和学术机构作邀请报告100余次，获美国NSF早期职业奖、NIH K02独立科学家奖、Grainger奖和Xerox奖等。

Abstract

Mechanical forces play crucial roles in regulating cellular functions, such as cell spreading, traction forces, and stem cell differentiation. However, it is not clear how they influence early cell signaling events such as calcium in living stem cells. Using highly-sensitive Ca2+ biosensors based on fluorescence resonance energy transfer (FRET), we investigated the molecular mechanism by which mechanical forces affect calcium signaling in human mesenchymal stem cells (HMSCs). Spontaneous Ca2+ oscillations were observed inside the cytoplasm and the endoplasmic reticulum (ER) using the FRET biosensors targeted at subcellular locations in cells plated on rigid dishes. Lowering the substrate stiffness to 1 kPa significantly inhibited both the magnitudes and frequencies of the cytoplasmic Ca2+ oscillation in comparison to stiffer or rigid substrate. This Ca2+ oscillation was shown to be dependent on ROCK, a downstream effector molecule of RhoA, but independent of actin filaments, microtubules, myosin light chain kinase, or myosin activity. Lysophosphatidic acid, which activates RhoA, also inhibited the frequency of the Ca2+ oscillation. Consistently, either a constitutive active mutant of RhoA (RhoA-V14) or a dominant negative mutant of RhoA (RhoA-N19) inhibited the Ca2+ oscillation. Further experiments revealed that HMSCs cultured on gels with low elastic moduli displayed low RhoA activities. Therefore, our results demonstrate that RhoA and its downstream molecule ROCK may mediate the substrate rigidity-regulated Ca2+ oscillation, which determines the physiological functions of HMSCs. We further investigated the molecular and biophysical mechanisms by which mechanical force regulates Ca2+ signaling at subcellular level in HMSCs, integrating optical laser tweezers and Ca2+ FRET biosensor. Laser-tweezer-traction on a fibronectin-coated bead at the plasma membrane induces intracellular Ca2+ oscillations caused by Ca2+ release from endoplasmic reticulum (ER) in the absence of extracellular Ca2+. Ca2+ oscillations produced by ER Ca2+ release upon mechanical force are mediated not only by the mechanical support of cytoskeleton and actomyosin contractility, but also by mechanosensitive Ca2+ channels on the plasma membrane, specifically TRPM7. As the ER Ca2+ release is inhibited, the mechanical force can induce intracellular Ca2+ increase via mechanosensitive Ca2+ channels in the presence of extracellular Ca2+, which is mediated by the cytoskeletal structure but not actomyosin contractility. Taken together, our results indicate that active actomyosin contractility is essential for the force transmission into the deep intracellular organelles, ER but dispensable for the mechanical regulation of plasma membrane channels. Therefore, our results clearly suggest a crucial role of mechanical force in regulating calcium signaling in live stem cells with a well-coordinated molecular hierarchy.