Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana.
Makromolekulare Chemie, TU Dresden, Dresden, Germany.
Biophys J. 2018 Jan 9;114(1):158-167. doi: 10.1016/j.bpj.2017.11.005.
The influence of cholesterol (CHOL) level on integrin sequestration in raft-mimicking lipid mixtures forming coexisting liquid-ordered (l) and liquid-disordered (l) lipid domains is investigated using complementary, single-molecule-sensitive, confocal detection methods. Systematic analysis of membrane protein distribution in such a model membrane environment demonstrates that variation of CHOL level has a profound influence on l-l sequestration of integrins, thereby exhibiting overall l preference in the absence of ligands and l affinity upon vitronectin addition. Accompanying photon-counting histogram analysis of integrins in the different model membrane mixtures shows that the observed changes of integrin sequestration in response to variations of membrane CHOL level are not associated with altering integrin oligomerization states. Instead, our experiments suggest that the strong CHOL dependence of integrin sequestration can be attributed to CHOL-mediated changes of lipid packing and bilayer thickness in coexisting l and l domains, highlighting the significance of a biophysical mechanism of CHOL-mediated regulation of integrin sequestration. We envision that this model membrane study may help clarify the influence of CHOL in integrin functionality in plasma membranes, thus providing further insight into the role of lipid heterogeneities in membrane protein distribution and function in a cellular membrane environment.
使用互补的、单分子敏感的共焦检测方法研究了胆固醇（CHOL）水平对拟筏脂质混合物中整合素隔离的影响，这些混合物形成共存的有序液体（l）和无序液体（l）脂质域。在这种模型膜环境中对膜蛋白分布的系统分析表明，CHOL 水平的变化对整合素的 l-l 隔离有深远的影响，因此在没有配体的情况下表现出整体 l 偏好，并且在添加 vitronectin 后表现出 l 亲和力。对不同模型膜混合物中整合素的光子计数直方图分析表明，观察到的整合素隔离响应膜 CHOL 水平变化的变化与改变整合素寡聚状态无关。相反，我们的实验表明，整合素隔离的强烈 CHOL 依赖性可归因于共存的 l 和 l 域中 CHOL 介导的脂质堆积和双层厚度的变化，突出了 CHOL 介导的整合素隔离调节的生物物理机制的重要性。我们设想，这项模型膜研究可能有助于阐明 CHOL 对质膜中整合素功能的影响，从而进一步了解脂质异质性在细胞膜环境中对膜蛋白分布和功能的作用。
