Plasma Membrane Rigidity Directly Influences Cell Migration

细胞生物力学的基础知识对于理解疾病的发展和进展是重要的。例如，人们已经认识到，癌细胞与健康细胞的不同之处在于剪切刚度降低。到目前为止，人们认为细胞骨架和细胞核的结构变化只决定细胞的生物力学性质。在这方面，还没有研究质膜的结构变化所起的作用。在本项目中，我们将分析质膜的脂质成分在多大程度上影响细胞的弯曲硬度和迁移行为。通过我们从临床样本获得的全球首个GPMV闪烁光谱研究，我们已经表明，分离的质膜的弯曲刚性与健康和恶性细胞的脂体之间存在相关性。在这个项目中，将全面研究导致质膜弯曲硬度变化的分子原因，以及这对细胞迁移行为的影响程度。本文的出发点是研究“巨型质膜囊泡”(GPMVS)的弯曲刚度与其分子组成之间的关系。GPMV是从细胞中分离出来的质膜，它基本上保持了细胞的复杂脂质成分，因此代表了一种合适的生理模型。在我们的项目中，GPMV是从莱比锡大学医院的乳腺癌患者的组织样本中获得的原代细胞产生的。为了便于比较，我们还将检查同一患者的健康上皮组织。为了补充对原代细胞的研究，我们将应用代表不同癌症阶段的乳腺癌细胞小组。GPMV的弯曲硬度将通过闪烁光谱来确定，磷脂的组成将通过质谱仪和核磁共振来确定。弯曲硬度与膜组成之间的相关性将增加对磷脂类物质影响膜硬度的认识。此外，我们还将选择性地探讨氧化修饰的膜脂对膜硬度的影响，因为“活性氧物种”(ROS)的形成在癌症发病机制中也起着至关重要的作用。质膜弹性与细胞迁移的相关性将通过单个细胞通过微通道的迁移来研究。通过探测细胞能够通过不同大小的孔的百分比，将根据膜的刚性来分析挤压通过时间以及通过后的运动类型。我们预计，膜硬度的降低有利于细胞通过狭窄的通道迁移。

The fundamental knowledge of cell biomechanics is important to understand the development and advancement of diseases. For instance, it has been recognised that cancer cells differ from healthy ones by a reduced shear stiffness. It has been assumed so far that structural changes of the cytoskeleton and the nucleus solely determine the biomechanical properties of cells. In this context it has not yet been examined which role structural changes of the plasma membrane are playing. In the present project we will analyse, to which extent the lipid composition of the plasma membrane influences the bending stiffness and the migration behaviour of cells. With our worldwide first flicker spectroscopy studies of GPMVs, obtained from clinical samples, we have already shown that there is a correlation between the bending rigidity of isolated plasma membranes and the lipidome of healthy and malignant cells. Within this project the molecular reasons which lead to the alteration of the bending stiffness of the plasma membrane and how far this influences the migration behaviour of cells will be comprehensively examined. The starting point is the investigation of the correlation between the bending stiffness and the molecular composition of "Giant Plasma Membrane Vesicles" (GPMVs). GPMVs are plasma membranes isolated from cells which maintain essentially their complex lipid composition and therefore represent a suitable physiological model. In our project GPMVs are generated from primary cells from tissue samples obtained from breast cancer patients from the Leipzig University hospital. For comparative purposes we will also examine healthy epithelial tissue from the same patient. To complement the investigations with primary cells we will apply a breast cancer cell panel which represents different stages of cancer. The bending stiffness of the GPMVs will be determined by flicker spectroscopy and the (phospho)lipid composition by mass spectrometry and NMR. The correlation between bending stiffness and membrane composition will increase the knowledge which (phospho)lipid classes influence membrane stiffness. In addition we will explore selectively the influence of oxidatively modified membrane lipids on membrane rigidity since the formation of “reactive oxygen species” (ROS) plays also a crucial role in cancer pathogenesis. The correlation of the plasma membrane elasticity and cell migration will be investigated by the migration of single cells through micro channels. By probing the percentage of cells that are able to pass through apertures of various sizes, the squeeze-through time, as well as type of motion after passage will be analyzed in correspondence to membrane rigidity. We expect that a decrease in membrane rigidity facilitates the cell migration through narrow channels.