Regulation of G protein-coupled cAMP receptor activation by a hydrophobic residue in transmembrane helix 3.
Regulation of G protein-coupled cAMP receptor activation by a hydrophobic residue in transmembrane helix 3.
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跨膜螺旋 3 中疏水残基对 G 蛋白偶联 cAMP 受体激活的调节。
DOI：
10.1111/j.1365-2958.2007.05803.x
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发表时间：
2007
影响因子：
3.6
通讯作者：
Hereld,Dale
中科院分区：
文献类型：
--
作者：
Zhang,Minghang;Goswami,Mousumi;Sawai,Satoshi;Cox,EdwardC;Hereld,Dale
cAR1 是一种 G 蛋白偶联 cAMP 受体，对于盘基网柄菌的多细胞发育至关重要。我们之前发现了一种 cAR1‐Ile104 突变体，由于其组成型磷酸化、对 cAMP 的亲和力升高、对发育的显性负效应以及需要适应的特定 cAR1 通路，该突变体似乎被组成型激活。为了研究 Ile104 如何调节 cAR1 激活，我们评估了用所有其他氨基酸替代它的后果。这些 Ile104 突变体的组成型磷酸化变化很大，表明它们被不同程度地激活，并且与取代氨基酸残基的极性相关。值得注意的是，除了最保守的替换之外，所有 Ile104 替换都显着提高了受体的 cAMP 亲和力。然而，只有三分之一的突变体（具有最多极性取代的突变体）阻碍了发育。这些发现与一个模型一致，其中极性 Ile104 取代扰乱了非活性和活性 cAR1 构象之间的平衡，有利于后者。基于与视紫红质的同源性，Ile104 可能埋藏在非活性 cAR1 内，并在激活后暴露于细胞质。我们认为疏水效应通常会促进 Ile104 的埋藏，从而促进 cAR1 失活，而 Ile104 的极性取代会减轻这种效应，从而导致 cAR1 活化。
cAR1, a G protein‐coupled cAMP receptor, is essential for multicellular development ofDictyostelium. We previously identified a cAR1‐Ile104mutant that appeared to be constitutively activated based on its constitutive phosphorylation, elevated affinity for cAMP, and dominant‐negative effects on development as well as specific cAR1 pathways that are subject to adaptation. To investigate how Ile104might regulate cAR1 activation, we assessed the consequences of substituting it with all other amino acids. Constitutive phosphorylation of these Ile104mutants varied broadly, suggesting that they are activated to varying extents, and was correlated with polarity of the substituting amino acid residue. Remarkably, all Ile104substitutions, except for the most conservative, dramatically elevated the receptor's cAMP affinity. However, only a third of the mutants (those with the most polar substitutions) blocked development. These findings are consistent with a model in which polar Ile104substitutions perturb the equilibrium between inactive and active cAR1 conformations in favour of the latter. Based on homology with rhodopsin, Ile104is likely buried within inactive cAR1 and exposed to the cytoplasm upon activation. We propose that the hydrophobic effect normally promotes burial of Ile104and hence cAR1 inactivation, while polar substitution of Ile104mitigates this effect, resulting in activation.