Mallipattu S K, Haidekker M A, Von Dassow P, Latz M I, Frangos J A
Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2002 Jun;188(5):409-16. doi: 10.1007/s00359-002-0315-9. Epub 2002 May 16.
Fluid shear stress has been demonstrated to affect the structure and function of various cell types. In mammalian cells, it was hypothesized that shear-induced membrane fluidization leads to activation of heterotrimetric G-proteins. The purpose of this study was to determine if a similar mechanism exists in the dinoflagellate Lingulodinium polyedrum, a single-celled eukaryotic aquatic organism that bioluminesces under shear stress. Membrane fluidity changes in L. polyedrum were monitored using the molecular rotor 9-(dicyanovinyl)-julolidine, whose fluorescence intensity changes inversely with membrane fluidity. Dual-staining with 9-(dicyanovinyl)-julolidine and the membrane dye 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate indicates membrane localization. Subjecting L. polyedrum cells to increasing shear stress reversibly decreased 9-(dicyanovinyl)-julolidine fluorescence, while autofluorescence of the cytoplasmic chlorophyll did not change. The relationship between shear stress (0.63 Pa, 1.25 Pa, 1.88 Pa, and 2.5 Pa) and membrane fluidity changes was linear and dose-dependent with a 12% increase in fluidity at 2.5 Pa. To further explore this mechanism a membrane fluidizing agent, dimethyl sulfoxide was added. Dimethyl sulfoxide decreased 9-(dicyanovinyl)-julolidine emission by 41+/-15% and elicited a dose-dependent bioluminescent response at concentrations of 0.2%, 0.5%, 1.0%, and 1.25%. This study demonstrates a link between fluid shear stress and membrane fluidity, and suggests that the membrane is an important flow mechanosensor of dinoflagellates.
流体剪切应力已被证明会影响各种细胞类型的结构和功能。在哺乳动物细胞中，有人推测剪切诱导的膜流动性增加会导致异三聚体G蛋白的激活。本研究的目的是确定在多甲藻属的夜光藻（一种在剪切应力下会发光的单细胞真核水生生物）中是否存在类似的机制。使用分子转子9-（二氰基乙烯基）-聚甲基丙烯酸甲酯监测多甲藻属的膜流动性变化，其荧光强度与膜流动性呈反比。用9-（二氰基乙烯基）-聚甲基丙烯酸甲酯和膜染料1-（4-三甲基铵苯基）-6-苯基-1,3,5-己三烯对甲苯磺酸盐进行双重染色表明其定位于膜上。对多甲藻属细胞施加逐渐增加的剪切应力会使9-（二氰基乙烯基）-聚甲基丙烯酸甲酯荧光可逆性降低，而细胞质叶绿素的自发荧光没有变化。剪切应力（0.63 Pa、1.25 Pa、1.88 Pa和2.5 Pa）与膜流动性变化之间的关系呈线性且剂量依赖性，在2.5 Pa时流动性增加12%。为了进一步探索这种机制，添加了一种膜流化剂二甲基亚砜。二甲基亚砜使9-（二氰基乙烯基）-聚甲基丙烯酸甲酯的发射降低了41±15%，并在浓度为0.2%、0.5%、1.0%和1.25%时引发了剂量依赖性的生物发光反应。本研究证明了流体剪切应力与膜流动性之间的联系，并表明膜是甲藻重要的流动机械传感器。
