Truelsen Sigurd Friis, Missel Julie Winkel, Gotfryd Kamil, Pedersen Per Amstrup, Gourdon Pontus, Lindorff-Larsen Kresten, Hélix-Nielsen Claus
Technical University of Denmark, Department of Environmental Engineering, Bygningstorvet Building 115, DK-2800 Kgs Lyngby, Denmark.
University of Copenhagen, Department of Biomedical Sciences, Nørre Allé 14, DK-2200 Copenhagen N, Denmark.
Biochim Biophys Acta Biomembr. 2022 Feb 1;1864(1):183809. doi: 10.1016/j.bbamem.2021.183809. Epub 2021 Oct 23.
Human aquaporin 10 (hAQP10) is an aquaglyceroporin that assists in maintaining glycerol flux in adipocytes during lipolysis at low pH. Hence, a molecular understanding of the pH-sensitive glycerol conductance may open up for drug development in obesity and metabolically related disorders. Control of hAQP10-mediated glycerol flux has been linked to the cytoplasmic end of the channel, where a unique loop is regulated by the protonation status of histidine 80 (H80). Here, we performed unbiased molecular dynamics simulations of three protonation states of H80 to unravel channel gating. Strikingly, at neutral pH, we identified a water coordination pattern with an inverted orientation of the water molecules in vicinity of the loop. Protonation of H80 results in a more hydrophobic loop conformation, causing loss of water coordination and leaving the pore often dehydrated. Our results indicate that the loss of such water interaction network may be integral for the destabilization of the loop in the closed configuration at low pH. Additionally, a residue unique to hAQP10 (F85) reveals structural importance by flipping into the channel in correlation with loop movements, indicating a loop-stabilizing role in the closed configuration. Taken together, our simulations suggest a unique gating mechanism combining complex interaction networks between water molecules and protein residues at the loop interface. Considering the role of hAQP10 in adipocytes, the detailed molecular insights of pH-regulation presented here will help to understand glycerol pathways in these cells and may assist in drug discovery for better management of human adiposity and obesity.
人类水通道蛋白10（hAQP10）是一种水甘油通道蛋白，在低pH值的脂肪分解过程中协助维持脂肪细胞中的甘油通量。因此，从分子层面理解pH敏感的甘油传导性可能为肥胖及代谢相关疾病的药物研发开辟道路。hAQP10介导的甘油通量控制与通道的胞质端有关，在该部位，一个独特的环受组氨酸80（H80）的质子化状态调节。在此，我们对H80的三种质子化状态进行了无偏分子动力学模拟，以揭示通道门控机制。令人惊讶的是，在中性pH值下，我们在该环附近发现了一种水分子取向倒置的水配位模式。H80质子化会导致环构象更疏水，导致水配位丧失，使孔道常常脱水。我们的结果表明，这种水相互作用网络的丧失可能是低pH值下环在关闭构型中不稳定的一个不可或缺的因素。此外，hAQP10特有的一个残基（F85）通过与环运动相关联而翻转进入通道，揭示了其结构重要性，表明在关闭构型中具有稳定环的作用。综上所述，我们的模拟结果表明了一种独特的门控机制，该机制结合了环界面处水分子与蛋白质残基之间复杂的相互作用网络。考虑到hAQP10在脂肪细胞中的作用，本文所呈现的关于pH调节的详细分子见解将有助于理解这些细胞中的甘油途径，并可能有助于发现更好管理人类肥胖症和肥胖的药物。
