Data from: Structural instability and divergence from conserved residues underlie intracellular retention of mammalian odorant receptors

Mammalian odorant receptors are a diverse and rapidly evolving set of G protein-coupled receptors expressed in olfactory cilia membranes. Most odorant receptors show little to no cell surface expression in non-olfactory cells due to endoplasmic reticulum retention, which has slowed down biochemical studies. Here, we provide evidence that structural instability and divergence from conserved residues of individual odorant receptors underlie intracellular retention using a combination of large-scale screening of odorant receptors cell surface expression in heterologous cells, point mutations, structural modeling, and machine learning techniques. We demonstrate the importance of conserved residues by synthesizing "consensus" odorant receptors that show high levels of cell surface expression similar to conventional G protein-coupled receptors. Furthermore, we associate in silico structural instability with poor cell surface expression using molecular dynamics simulations. We propose an enhanced evolutionary capacitance of olfactory sensory neurons that enable the functional expression of odorant receptors with cryptic mutations.

哺乳动物气味受体是一类多样性丰富且演化迅速的G蛋白偶联受体（G protein-coupled receptors），特异性表达于嗅觉纤毛膜中。大多数气味受体因内质网滞留效应，在非嗅觉细胞中几乎无法或完全无法实现细胞表面表达，这一瓶颈极大阻碍了生物化学相关研究的推进。本研究结合异源细胞中气味受体细胞表面表达的大规模筛选、点突变、结构建模以及机器学习技术，提供了确凿证据：单个气味受体的结构不稳定性以及与保守残基的序列差异，正是其发生细胞内滞留的根本诱因。我们通过合成"consensus"型气味受体，验证了保守残基的关键作用——这类受体可实现与常规G蛋白偶联受体相当的高水平细胞表面表达。此外，我们借助分子动力学模拟，将计算机模拟（in silico）所得的结构不稳定性与细胞表面表达水平低下建立了明确关联。本研究提出：嗅觉感觉神经元具备增强的进化电容，可使携带隐秘突变的气味受体实现功能性表达。