Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Int J Mol Sci. 2024 Feb 12;25(4):2204. doi: 10.3390/ijms25042204.
Using the gramicidin A channel as a molecular probe, we show that tubulin binding to planar lipid membranes changes the channel kinetics-seen as an increase in the lifetime of the channel dimer-and thus points towards modification of the membrane's mechanical properties. The effect is more pronounced in the presence of non-lamellar lipids in the lipid mixture used for membrane formation. To interpret these findings, we propose that tubulin binding redistributes the lateral pressure of lipid packing along the membrane depth, making it closer to the profile expected for lamellar lipids. This redistribution happens because tubulin perturbs the lipid headgroup spacing to reach the membrane's hydrophobic core via its amphiphilic α-helical domain. Specifically, it increases the forces of repulsion between the lipid headgroups and reduces such forces in the hydrophobic region. We suggest that the effect is reciprocal, meaning that alterations in lipid bilayer mechanics caused by membrane remodeling during cell proliferation in disease and development may also modulate tubulin membrane binding, thus exerting regulatory functions. One of those functions includes the regulation of protein-protein interactions at the membrane surface, as exemplified by VDAC complexation with tubulin.
我们使用短杆菌肽 A 通道作为分子探针,发现微管蛋白与平面脂膜结合会改变通道动力学——表现为通道二聚体寿命的延长——这表明膜的力学性质发生了改变。在用于形成膜的脂质混合物中存在非层状脂质时,这种效应更为明显。为了解释这些发现,我们提出微管蛋白结合重新分配了脂质堆积的侧向压力沿膜深度的分布,使其更接近层状脂质的预期分布。这种重新分布是因为微管蛋白通过其两亲性α-螺旋结构域扰乱了脂质头部基团的间距,以到达膜的疏水区。具体来说,它增加了脂质头部基团之间的排斥力,并减少了疏水区的这种力。我们认为这种效应是相互的,这意味着疾病和发育过程中细胞增殖期间的膜重塑引起的脂质双层力学变化也可能调节微管蛋白与膜的结合,从而发挥调节功能。其中一个功能包括调节膜表面的蛋白质-蛋白质相互作用,例如 VDAC 与微管蛋白的复合物。