Wu Han, Feng Xuhui, Wang Meng, Gui Tianxiang, Fu Mingfeng, Zheng Mengmeng, Huang Zixuan, Luo Xudong, Liu Ying, Chen Li-Ming
Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science & Technology, Huazhong University of Science & Technology, Wuhan, China.
Institute of Biomedicine and Hubei Key Laboratory of Embryonic Stem Cell Research, College of Basic Medicine, Hubei University of Medicine, Shiyan, China.
Commun Biol. 2025 Aug 28;8(1):1295. doi: 10.1038/s42003-025-08713-5.
The solute carriers (SLC) superfamily comprises 66 families with more than 450 members. The Na/ cotransporter NBCe1 (SLC4A4) of SLC4 family plays critical roles in intracellular pH regulation and transepithelial transport of fluid and electrolytes. Here, we explored the structural mechanisms of NBCe1-A regulation by two phosphorylation modules: P-loop in the amino-terminal domain and H-loop in the transmembrane domain. Mimic-phosphorylation of P-loop or H-loop substantially decreases NBCe1-A activity. Inhibition of NBCe1 by P-loop is abolished by mutations to specific basic residues in the fourth intracellular loop (IL4) in the carrier domain and IL3/IL6 in the scaffold. Inhibition by H-loop is abolished by specific mutations to IL3. We conclude that: (1) P-loop inactivates NBCe1-A by binding to the carrier and the scaffold; (2) H-loop blocks NBCe1-A by interacting with IL3 in the scaffold. Our findings have implications for studying the structural mechanisms for the regulation of other SLCs by phosphorylation.
溶质载体（SLC）超家族由66个家族组成，成员超过450个。SLC4家族的Na/共转运体NBCe1（SLC4A4）在细胞内pH调节以及液体和电解质的跨上皮转运中发挥关键作用。在此，我们探讨了两个磷酸化模块对NBCe1-A的调节结构机制：氨基末端结构域中的P环和跨膜结构域中的H环。P环或H环的模拟磷酸化会显著降低NBCe1-A的活性。载体结构域中第四细胞内环（IL4）以及支架中IL3/IL6的特定碱性残基发生突变后，可消除P环对NBCe1的抑制作用。IL3的特定突变可消除H环的抑制作用。我们得出以下结论：（1）P环通过与载体和支架结合使NBCe1-A失活；（2）H环通过与支架中的IL3相互作用来阻断NBCe1-A。我们的研究结果对于研究磷酸化调节其他SLC的结构机制具有重要意义。
