Uchiyama Makoto, Nakao Akito, Kurita Yuki, Fukushi Isato, Takeda Kotaro, Numata Tomohiro, Tran Ha Nam, Sawamura Seishiro, Ebert Maximilian, Kurokawa Tatsuki, Sakaguchi Reiko, Stokes Alexander J, Takahashi Nobuaki, Okada Yasumasa, Mori Yasuo
Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
Clinical Research Center, Murayama Medical Center, Musashimurayama, Tokyo 208-0011, Japan; Faculty of Health Sciences, Uekusa Gakuen University, Chiba 264-0007, Japan.
Curr Biol. 2020 Sep 7;30(17):3378-3396.e7. doi: 10.1016/j.cub.2020.06.047. Epub 2020 Jul 16.
Hypoxia sensors are essential for regulating local oxygen (O) homeostasis within the body. This is especially pertinent within the CNS, which is particularly vulnerable to O deprivation due to high energetic demand. Here, we reveal hypoxia-monitoring function exerted by astrocytes through an O-regulated protein trafficking mechanism within the CNS. Strikingly, cultured mouse astrocytes isolated from the parafacial respiratory group (pFRG) and retrotrapezoid nucleus (RTN) region are capable of rapidly responding to moderate hypoxia via the sensor cation channel transient receptor potential (TRP) A1 but, unlike multimodal sensory neurons, are inert to hyperoxia and other TRPA1 activators (carbon dioxide, electrophiles, and oxidants) in normoxia. Mechanistically, O suppresses TRPA1 channel activity by protein internalization via O-dependent proline hydroxylation and subsequent ubiquitination by an E3 ubiquitin ligase, NEDD4-1 (neural precursor cell-expressed developmentally down-regulated protein 4). Hypoxia inhibits this process and instantly accumulates TRPA1 proteins at the plasma membrane, inducing TRPA1-mediated Ca influx that triggers ATP release from pFRG/RTN astrocytes, potentiating respiratory center activity. Furthermore, astrocyte-specific Trpa1 disruption in a mouse brainstem-spinal cord preparation impedes the amplitude augmentation of the central autonomic respiratory output during hypoxia. Thus, reversible coupling of the TRPA1 channels with O-dependent protein translocation allows astrocytes to act as acute hypoxia sensors in the medullary respiratory center.
缺氧传感器对于调节体内局部氧（O）稳态至关重要。这在中枢神经系统（CNS）中尤为相关，由于高能量需求，中枢神经系统特别容易受到氧剥夺的影响。在这里，我们揭示了星形胶质细胞通过中枢神经系统内一种受氧调节的蛋白质转运机制发挥的缺氧监测功能。令人惊讶的是，从面神经旁呼吸组（pFRG）和延髓背外侧网状核（RTN）区域分离的培养小鼠星形胶质细胞能够通过传感器阳离子通道瞬时受体电位（TRP）A1对中度缺氧做出快速反应，但与多模式感觉神经元不同，在常氧条件下对高氧和其他TRPA1激活剂（二氧化碳、亲电试剂和氧化剂）无反应。从机制上讲，氧通过依赖氧的脯氨酸羟化作用使蛋白质内化，并随后由E3泛素连接酶NEDD4-1（神经前体细胞表达的发育下调蛋白4）进行泛素化，从而抑制TRPA1通道活性。缺氧抑制这一过程，并使TRPA1蛋白立即在质膜上积累，诱导TRPA1介导的Ca内流，触发pFRG/RTN星形胶质细胞释放ATP，增强呼吸中枢活动。此外，在小鼠脑干-脊髓制剂中星形胶质细胞特异性Trpa1破坏会阻碍缺氧期间中枢自主呼吸输出的幅度增加。因此，TRPA1通道与依赖氧的蛋白质转运的可逆偶联使星形胶质细胞能够作为延髓呼吸中枢中的急性缺氧传感器。
