Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY.
Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY.
J Gen Physiol. 2019 Mar 4;151(3):342-356. doi: 10.1085/jgp.201812263. Epub 2019 Feb 22.
The two major classes of antidepressants, tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), inhibit neurotransmitter reuptake at synapses. They also have off-target effects on proteins other than neurotransmitter transporters, which may contribute to both desired changes in brain function and the development of side effects. Many proteins modulated by antidepressants are bilayer spanning and coupled to the bilayer through hydrophobic interactions such that the conformational changes underlying their function will perturb the surrounding lipid bilayer, with an energetic cost (Δ ) that varies with changes in bilayer properties. Here, we test whether changes in Δ caused by amphiphilic antidepressants partitioning into the bilayer are sufficient to alter membrane protein function. Using gramicidin A (gA) channels to probe whether TCAs and SSRIs alter the bilayer contribution to the free energy difference for the gramicidin monomer⇔dimer equilibrium (representing a well-defined conformational transition), we find that antidepressants alter gA channel activity with varying potency and no stereospecificity but with different effects on bilayer elasticity and intrinsic curvature. Measuring the antidepressant partition coefficients using isothermal titration calorimetry (ITC) or cLogP shows that the bilayer-modifying potency is predicted quite well by the ITC-determined partition coefficients, and channel activity is doubled at an antidepressant/lipid mole ratio of 0.02-0.07. These results suggest a mechanism by which antidepressants could alter the function of diverse membrane proteins by partitioning into cell membranes and thereby altering the bilayer contribution to the energetics of membrane protein conformational changes.
两类主要的抗抑郁药，三环抗抑郁药（TCAs）和选择性 5-羟色胺再摄取抑制剂（SSRIs），在突触处抑制神经递质的再摄取。它们也对除神经递质转运体以外的蛋白质有非靶向作用，这可能有助于大脑功能的理想变化和副作用的发展。许多受抗抑郁药调节的蛋白质是双层跨膜的，并通过疏水性相互作用与双层连接，使得其功能的构象变化将扰乱周围的脂质双层，具有不同的能量成本（Δ），这取决于双层性质的变化。在这里，我们测试了通过双层分配进入双层的两亲性抗抑郁药引起的Δ变化是否足以改变膜蛋白的功能。使用短杆菌肽 A（gA）通道来探测 TCAs 和 SSRIs 是否改变了对革兰氏单体⇔二聚体平衡的自由能差的双层贡献（代表一个明确的构象转变），我们发现抗抑郁药以不同的效力和非立体特异性改变 gA 通道的活性，但对双层弹性和固有曲率有不同的影响。使用等温滴定微量热法（ITC）或 cLogP 测量抗抑郁药的分配系数，发现双层修饰效力可以通过 ITC 确定的分配系数很好地预测，并且在抗抑郁药/脂质摩尔比为 0.02-0.07 时，通道活性增加一倍。这些结果表明了一种机制，即抗抑郁药可以通过分配到细胞膜中来改变不同膜蛋白的功能，从而改变双层对膜蛋白构象变化的能量贡献。
