Chung Man-Kyo, Lee Jongseok, Joseph John, Saloman Jami, Ro Jin Y
Department of Neural and Pain Sciences, Program in Neuroscience, University of Maryland School of Dentistry, Baltimore, Maryland.
Department of Neural and Pain Sciences, Program in Neuroscience, University of Maryland School of Dentistry, Baltimore, Maryland.
J Pain. 2015 Jan;16(1):67-76. doi: 10.1016/j.jpain.2014.10.008. Epub 2014 Nov 1.
Elevated glutamate levels within injured muscle play important roles in muscle pain and hyperalgesia. In this study, we hypothesized that protein kinase C (PKC)-dependent TRPV1 phosphorylation contributes to the muscle mechanical hyperalgesia following activation of Group I metabotropic glutamate receptors (mGlu1/5). Mechanical hyperalgesia induced by (R,S)-3,5-dihydroxyphenylglycine (DHPG), an mGlu1/5 agonist, in the masseter muscle was attenuated by AMG9810, a specific TRPV1 antagonist. AMG9810 also suppressed mechanical hyperalgesia evoked by pharmacologic activation of PKC. DHPG-induced mechanical hyperalgesia was suppressed by pretreatment with a decoy peptide that disrupted interactions between TRPV1 and A-kinase-anchoring protein (AKAP), which facilitates phosphorylation of TRPV1. In dissociated trigeminal ganglia, DHPG upregulated serine phosphorylation of TRPV1 (S800), during which DHPG-induced mechanical hyperalgesia was prominent. The TRPV1 phosphorylation at S800 was suppressed by a PKC inhibitor. Electrophysiologic measurements in trigeminal ganglion neurons demonstrated that TRPV1 sensitivity was enhanced by pretreatment with DHPG, and this was prevented by a PKC inhibitor, but not by a protein kinase A inhibitor. These results suggest that mGlu1/5 activation in masseter afferents invokes phosphorylation of TRPV1 serine residues including S800, and that phosphorylation-induced sensitization of TRPV1 is involved in masseter mechanical hyperalgesia. These data support a role of TRPV1 as an integrator of glutamate receptor signaling in muscle nociceptors.
This article demonstrates that activation of mGlu1/5 leads to phosphorylation of a specific TRPV1 residue via PKC and AKAP150 in trigeminal sensory neurons and that functional interactions between glutamate receptors and TRPV1 mediate mechanical hyperalgesia in the muscle tissue.
损伤肌肉内谷氨酸水平升高在肌肉疼痛和痛觉过敏中起重要作用。在本研究中，我们假设蛋白激酶C（PKC）依赖性TRPV1磷酸化促成了I组代谢型谷氨酸受体（mGlu1/5）激活后的肌肉机械性痛觉过敏。mGlu1/5激动剂（R，S）-3,5-二羟基苯甘氨酸（DHPG）在咬肌中诱导的机械性痛觉过敏被特异性TRPV1拮抗剂AMG9810减弱。AMG9810也抑制了PKC药理学激活诱发的机械性痛觉过敏。用干扰TRPV1与A激酶锚定蛋白（AKAP）相互作用的诱饵肽预处理可抑制DHPG诱导的机械性痛觉过敏，AKAP有助于TRPV1的磷酸化。在解离的三叉神经节中，DHPG上调了TRPV1的丝氨酸磷酸化（S800），在此期间DHPG诱导的机械性痛觉过敏很明显。S800处的TRPV磷酸化被PKC抑制剂抑制。三叉神经节神经元的电生理测量表明，用DHPG预处理可增强TRPV1敏感性，而PKC抑制剂可阻止这种增强，但蛋白激酶A抑制剂则不能。这些结果表明，咬肌传入纤维中的mGlu1/5激活会引发包括S800在内的TRPV1丝氨酸残基的磷酸化，并且TRPV1磷酸化诱导的敏化参与咬肌机械性痛觉过敏。这些数据支持TRPV1作为肌肉伤害感受器中谷氨酸受体信号整合器的作用。
本文证明mGlu1/5的激活通过三叉神经感觉神经元中的PKC和AKAP150导致特定TRPV1残基的磷酸化，并且谷氨酸受体与TRPV1之间的功能相互作用介导了肌肉组织中的机械性痛觉过敏。
