Balleza Daniel, Sacchi Mattia, Vena Giulia, Galloni Debora, Puia Giulia, Facci Paolo, Alessandrini Andrea
CNR - Istituto Nanoscienze, S3, Via Campi 213/A, 41125, Italy.
Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Via Campi 213/A, 41125 Modena, Italy.
Biochim Biophys Acta. 2015 May;1848(5):1268-76. doi: 10.1016/j.bbamem.2015.01.017. Epub 2015 Feb 3.
Amphiphilic molecules supposed to affect membrane protein activity could strongly interact also with the lipid component of the membrane itself. Neurosteroids are amphiphilic molecules that bind to plasma membrane receptors of cells in the central nervous system but their effect on membrane is still under debate. For this reason it is interesting to investigate their effects on pure lipid bilayers as model systems. Using the micropipette aspiration technique (MAT), here we studied the effects of a neurosteroid, allopregnanolone (3α,5α-tetrahydroprogesterone or Allo) and of one of its isoforms, isoallopregnanolone (3β,5α-tetrahydroprogesterone or isoAllo), on the physical properties of pure lipid bilayers composed by DOPC/bSM/chol. Allo is a well-known positive allosteric modulator of GABAA receptor activity while isoAllo acts as a non-competitive functional antagonist of Allo modulation. We found that Allo, when applied at nanomolar concentrations (50-200 nM) to a lipid bilayer model system including cholesterol, induces an increase of the lipid bilayer area and a decrease of the mechanical parameters. Conversely, isoAllo, decreases the lipid bilayer area and, when applied, at the same nanomolar concentrations, it does not affect significantly its mechanical parameters. We characterized the kinetics of Allo uptake by the lipid bilayer and we also discussed its aspects in relation to the slow kinetics of Allo gating effects on GABAA receptors. The overall results presented here show that a correlation exists between the modulation of Allo and isoAllo of GABAA receptor activity and their effects on a lipid bilayer model system containing cholesterol.
据推测，能够影响膜蛋白活性的两亲性分子也可能与膜自身的脂质成分发生强烈相互作用。神经甾体是一类两亲性分子，它们可与中枢神经系统细胞的质膜受体结合，但其对膜的影响仍存在争议。因此，研究它们对作为模型系统的纯脂质双层的影响很有意思。在这里，我们使用微量移液器抽吸技术（MAT），研究了一种神经甾体别孕烯醇酮（3α,5α - 四氢孕酮或Allo）及其一种异构体异别孕烯醇酮（3β,5α - 四氢孕酮或isoAllo）对由二油酰磷脂酰胆碱/牛磺胆酸钠/胆固醇（DOPC/bSM/chol）组成的纯脂质双层物理性质的影响。Allo是一种众所周知的GABAA受体活性的正变构调节剂，而异构体isoAllo则作为Allo调节的非竞争性功能拮抗剂。我们发现，当以纳摩尔浓度（50 - 200 nM）将Allo应用于包含胆固醇的脂质双层模型系统时，会导致脂质双层面积增加以及力学参数降低。相反，isoAllo会减小脂质双层面积，并且当以相同的纳摩尔浓度应用时，它对其力学参数没有显著影响。我们表征了脂质双层摄取Allo的动力学，并讨论了其与Allo对GABAA受体门控效应的缓慢动力学相关的方面。此处呈现的总体结果表明，GABAA受体活性的Allo和isoAllo调节与其对包含胆固醇的脂质双层模型系统的影响之间存在相关性。
