From the Department of Molecular Pharmacology, School of Pharmacy, Lanzhou University, Lanzhou, Gansu, People's Republic of China.
Anesthesiology. 2015 Mar;122(3):686-97. doi: 10.1097/ALN.0000000000000532.
The reduction of γ-aminobutyric acid (GABA) type A receptor-mediated inhibition has long been implicated in spinal sensitization of nociceptive responses. However, it is largely unknown which signaling cascades in spinal dorsal horn neurons are initiated by the reduced inhibition to trigger pain hypersensitivity.
GABAergic inhibition was manipulated by intrathecal application of GABA type A receptor antagonist bicuculline in intact mice or by GABA type A receptor agonist muscimol in complete Freund's adjuvant-injected mice. Immunoblotting, coimmunoprecipitation, immunohistochemistry, and behavioral tests were used to explore the signaling pathways downstream of the altered GABAergic tone.
The study data revealed that the 61-kD isoform of striatal-enriched protein phosphatase (STEP61) was a key molecule that relayed the signals from GABAergic neurotransmission. The authors found that STEP61 was highly expressed in dorsal horn neurons. Under physiological conditions, STEP61 tonically interacted with and negatively controlled the activities of extracellular signal-regulated kinase and Src-family protein tyrosine kinases member Fyn, two critical kinases involved in spinal sensitization. Once GABAergic inhibition was impaired, STEP61 interaction with its substrates was substantially disturbed, allowing for activation of extracellular signal-regulated kinase and Fyn (n = 4 to 6). The hyperactivities of extracellular signal-regulated kinase and Fyn, along with STEP61 dysregulation, caused the tyrosine phosphorylation and synaptic accumulation of GluN2B subunit-containing N-methyl-D-aspartate subtype of glutamate receptors (n = 6), leading to GluN2B receptor-dependent pain hypersensitivity. Overexpression of wild-type STEP61 to resume its enzymatic activity significantly blocked the mechanical allodynia evoked by bicuculline and more importantly, alleviated chronic inflammatory pain (n = 6 in each group).
These data identified STEP61 as a key intermediary for GABAergic inhibition to regulate pain sensitization.
γ-氨基丁酸（GABA）A型受体介导的抑制作用减弱与伤害性感受反应的脊髓敏化有关。然而，脊髓背角神经元中哪些信号级联反应是由抑制作用减弱引发疼痛敏化尚不清楚。
在完整小鼠中鞘内应用 GABA 型 A 受体拮抗剂荷包牡丹碱或在完全弗氏佐剂注射小鼠中应用 GABA 型 A 受体激动剂 muscimol 来操纵 GABA 能抑制。采用免疫印迹、共免疫沉淀、免疫组织化学和行为学测试来探索改变的 GABA 能张力下游的信号通路。
研究数据表明，纹状体丰富蛋白磷酸酶 61-kD 同工型（STEP61）是一种关键分子，它传递 GABA 能神经传递的信号。作者发现 STEP61 在背角神经元中高度表达。在生理条件下，STEP61 与细胞外信号调节激酶和Src 家族蛋白酪氨酸激酶成员 Fyn 这两种参与脊髓敏化的关键激酶的活性持续相互作用并负调控其活性。一旦 GABA 能抑制受损，STEP61 与其底物的相互作用会受到严重干扰，导致细胞外信号调节激酶和 Fyn 的激活（n = 4 至 6）。细胞外信号调节激酶和 Fyn 的过度激活以及 STEP61 的失调导致包含 GluN2B 亚基的 N-甲基-D-天冬氨酸型谷氨酸受体的酪氨酸磷酸化和突触累积（n = 6），导致 GluN2B 受体依赖性疼痛敏化。野生型 STEP61 的过表达以恢复其酶活性可显著阻断荷包牡丹碱引起的机械性痛觉过敏，更重要的是，缓解慢性炎症性疼痛（每组 n = 6）。
这些数据确定 STEP61 是 GABA 能抑制作用调节疼痛敏化的关键中介物。
