Curvature and Composition Regulation in Tubular Lipid Membranes: A Biophysical Investigation

管状脂质膜的曲率和成分调节：生物物理研究

• 批准号: 0718569
• 负责人: Tobias Baumgart
• 金额: $ 75.98万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0718569&HistoricalAwards=false
• 关键词: Curvature; Composition; Regulation; Tubular; Lipid

Remarkable progress has recently been made in uncovering phenomena that are related to the shape of lipid and lipid/protein membranes. Biological science has recognized the importance of membrane curvature: rather than being a passive matrix that is shaped by external factors, its active participation in processes as important as membrane sorting and trafficking has been realized. Findings from theoretical membrane physics and cell membrane biology have generated an urge to fill the gap between quantitative theories (with insufficient experimental realization) and qualitative descriptions (with missing biophysical measurements). The current impasse is particularly evident in research centered on a recently discovered, potentially ubiquitously important, curvature generating and sensing module, the BAR domain. This banana shaped protein domain is qualitatively observed to cause membranes to assume the shape of cylindrical tubes with varying curvature, but with incompletely understood mechanism and absence of elucidation of the mechanics involved. These and other types of isolated modules will serve as a starting point for systematic investigation of membrane shaping factors. A hiatus of membrane curvature research has been the focus on microscopically resolvable curvature radii of multiple micron sized (giant) vesicles. Technically significantly more challenging (and hence under-explored), but relevant for biological membrane curvatures, is the investigation of mechanical aspects of membrane tubes, where high precision measurement of nanometer scale curvature can be conveniently combined with the measurement of mechanical force/moment equilibria modulated by lipid/protein interactions. Membrane tubes pulled from giant vesicles represent a mechanically controllable membrane system with a steep, precisely adjustable curvature gradient. These tubes will allow addressing a second fundamental problem where theoretical and biological models have not been sufficiently connected through quantitative data. The question to be explored regards to what extent, and based on which molecular details, membrane components are sorted in membrane curvature gradients, to clarify how this biophysical sorting could be involved in intracellular membrane sorting and trafficking. Beginning with curvature dependent lateral sorting of fluorescent lipids, and extending to peripheral and transmembrane protein sorting, the PI will quantify aspects of curvature sorting and characterize and develop curvature sensors that may be used in the cellular context. Synergistically coupled to the PI's research objectives is the involvement and education particularly of undergraduate level students in research projects, enriched by research opportunities for high school students, including minority groups, and teachers, an activity which is harmoniously integrated into long established outreach programs of the NSF funded UPenn MRSEC center, as well as an ACS funded project SEED. Further educational objectives include the integration of the teaching of science ethics into classes directed towards undergraduate and graduate students. This aspect will include discussion of scientific misconduct examples that received media coverage, as well as common gray area cases like opportunities and boundaries of image processing techniques. Furthermore, the PI will integrate methods to use the scientific software Matlab for illustrating both statistical concepts, as well as fundamental aspects of image analysis in teaching and research.

最近在揭示与脂膜和脂膜/蛋白膜形状有关的现象方面取得了显著进展。生物科学已经认识到膜弯曲的重要性：它不是一个由外部因素塑造的被动基质，而是实现了它主动参与与膜分类和贩运一样重要的过程。理论膜物理和细胞膜生物学的发现促使人们迫切需要填补定量理论(实验认识不足)和定性描述(缺少生物物理测量)之间的空白。目前的僵局在以最近发现的、可能无处不在的重要曲率生成和传感模块--杆域为中心的研究中尤为明显。这种香蕉状的蛋白质结构域被定性地观察到导致膜呈现不同曲率的圆柱管的形状，但机制尚不完全清楚，所涉及的机制也缺乏阐明。这些和其他类型的分离组件将作为系统研究膜成形因素的起点。多微米大小(巨型)囊泡的显微可分辨曲率半径一直是膜曲率研究的一个空白。在技术上更具挑战性(因此未被探索)，但与生物膜曲率相关的是膜管的机械方面的研究，其中纳米级曲率的高精度测量可以方便地与由脂质/蛋白质相互作用调节的机械力/力矩平衡的测量相结合。从巨大的囊泡中拉出的膜管代表了一种机械可控的膜系统，具有陡峭的、精确可调的曲率梯度。这些试管将解决第二个根本问题，即理论模型和生物模型没有通过定量数据充分联系起来。需要探索的问题是，膜组分在多大程度上，以及基于哪些分子细节，在膜曲率梯度中进行分类，以澄清这种生物物理分类如何参与细胞内膜的分类和运输。从依赖曲率的荧光脂类横向分选开始，扩展到外周和跨膜蛋白质分选，PI将量化曲率分选的各个方面，并表征和开发可用于细胞环境的曲率传感器。与PI的研究目标协同结合的是参与和教育研究项目，特别是本科生参与研究项目，为高中生，包括少数群体和教师提供研究机会，这一活动和谐地整合到NSF资助的UPenn MRSEC中心的长期推广计划中，以及ACS资助的项目种子。进一步的教育目标包括将科学伦理学教学纳入针对本科生和研究生的课堂。这方面将包括讨论受到媒体报道的科学不端行为例子，以及图像处理技术的机会和边界等常见的灰色地带案例。此外，PI将整合各种方法，使用科学软件MatLab来说明统计概念以及图像分析在教学和研究中的基本方面。