Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Elife. 2022 Mar 15;11:e71931. doi: 10.7554/eLife.71931.
The growth plates are cartilage tissues found at both ends of developing bones, and vital proliferation and differentiation of growth plate chondrocytes are primarily responsible for bone growth. C-type natriuretic peptide (CNP) stimulates bone growth by activating natriuretic peptide receptor 2 (NPR2) which is equipped with guanylate cyclase on the cytoplasmic side, but its signaling pathway is unclear in growth plate chondrocytes. We previously reported that transient receptor potential melastatin-like 7 (TRPM7) channels mediate intermissive Ca influx in growth plate chondrocytes, leading to activation of Ca/calmodulin-dependent protein kinase II (CaMKII) for promoting bone growth. In this report, we provide evidence from experiments using mutant mice, indicating a functional link between CNP and TRPM7 channels. Our pharmacological data suggest that CNP-evoked NPR2 activation elevates cellular cGMP content and stimulates big-conductance Ca-dependent K (BK) channels as a substrate for cGMP-dependent protein kinase (PKG). BK channel-induced hyperpolarization likely enhances the driving force of TRPM7-mediated Ca entry and seems to accordingly activate CaMKII. Indeed, ex vivo organ culture analysis indicates that CNP-facilitated bone growth is abolished by chondrocyte-specific gene ablation. The defined CNP signaling pathway, the NPR2-PKG-BK channel-TRPM7 channel-CaMKII axis, likely pinpoints promising target proteins for developing new therapeutic treatments for divergent growth disorders.
生长板是位于发育中骨骼两端的软骨组织,生长板软骨细胞的重要增殖和分化是骨骼生长的主要原因。C 型利钠肽 (CNP) 通过激活具有细胞质侧鸟苷酸环化酶的利钠肽受体 2 (NPR2) 刺激骨骼生长,但在生长板软骨细胞中其信号通路尚不清楚。我们之前的研究报道,瞬时受体电位 melastatin 样 7 型 (TRPM7) 通道介导生长板软骨细胞间歇性的 Ca2+内流,导致 Ca2+/钙调蛋白依赖性蛋白激酶 II (CaMKII) 的激活,从而促进骨骼生长。在本报告中,我们通过使用突变小鼠的实验提供了证据,表明 CNP 和 TRPM7 通道之间存在功能联系。我们的药理学数据表明,CNP 诱导的 NPR2 激活会增加细胞内 cGMP 含量,并刺激大电导钙依赖性 K (BK) 通道作为 cGMP 依赖性蛋白激酶 (PKG) 的底物。BK 通道诱导的超极化可能增强了 TRPM7 介导的 Ca2+内流的驱动力,并似乎相应地激活了 CaMKII。事实上,离体器官培养分析表明,CNP 促进的骨骼生长被软骨细胞特异性基因缺失所消除。定义明确的 CNP 信号通路,即 NPR2-PKG-BK 通道-TRPM7 通道-CaMKII 轴,可能为开发治疗不同生长障碍的新治疗方法指明了有希望的靶蛋白。
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