A peptide comprising the juxtamembrane C‐terminal intracellular loop 4 (IL4) of the CB₁ cannabinoid receptor possesses three serine residues (Ser402, Ser411, and Ser415). We report the effect of Ser phosphorylation on the CB₁ IL4 peptide conformation and cellular signaling functions using nuclear magnetic resonance spectroscopy, circular dichroism (CD), G protein activation, and cyclic adenosine monophosphate (cAMP) production. Phosphorylation at Ser residues induced helical structure in different environments. Helical content varies in the order of IL4p‐Ser411 > IL4pSer415 > IL4 > IL4pSer402. The efficacy of phosphorylated IL4 peptides in activating Go and Gi3 ([³⁵S]GTPγS binding) and inhibiting cAMP accumulation in N18TG2 cells was correlated with helicity changes. Bradykinin treatment, which activates protein kinase C (PKC), augmented CB₁‐mediated inhibition of cAMP accumulation, and this was reversed by a PKC inhibitor. We conclude that phosphorylation‐dependent alterations of helicity of CB₁ IL4 peptides can augment G protein signaling.

中文翻译：

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CB1大麻素受体磷酸化的第四细胞内环结构-功能关系。

包含CB ₁大麻素受体的近膜C末端细胞内环4（IL4）的肽具有三个丝氨酸残基（Ser402，Ser411和Ser415）。我们报告了使用核磁共振波谱，圆二色性（CD），G蛋白激活和环状单磷酸腺苷（cAMP）生产的Ser磷酸化对CB ₁ IL4肽构象和细胞信号传导功能的影响。Ser残基的磷酸化在不同环境下诱导螺旋结构。螺旋含量的变化顺序为：IL4p-Ser411> IL4pSer415> IL4> IL4pSer402。磷酸化的IL4肽在激活Go和Gi3（[ ³⁵S]GTPγS结合）和抑制cAMP在N18TG2细胞中的积累与螺旋度变化相关。缓激肽治疗可激活蛋白激酶C（PKC），增强CB ₁介导的cAMP积累抑制作用，而PKC抑制剂可逆转这种作用。我们得出结论，CB ₁ IL4肽的螺旋度依赖磷酸化改变可以增强G蛋白信号传导。