The Arabidopsis heterotrimeric G protein α subunit binds to and inhibits the inward rectifying potassium channel KAT1

• Published in: Plant science (Limerick) 2024-12, Vol.352, p.112363, Article 112363
• Main Authors: Guo, Jiang-Fan, Zhou, Hui, Hu, Zhuo-Ran, Yang, Ya-Lan, Wang, Wen-Bin, Zhang, Yan-Ru, Li, Xue, Mulati, Nuerkaimaier, Li, Ying-Xin, Wu, Lu, Long, Yu, He, Jun-Min
• Format: Article
• Language: English
• Subjects: Gα subunit; heterotrimer G proteins; interaction; inward-rectifying K+ channels; potassium channel in Arabidopsis thaliana 1; transmembrane domains
• ISSN: 0168-9452; 1873-2259; 1873-2259
• DOI: 10.1016/j.plantsci.2024.112363

In animal cells, Gα subunit of the heterotrimeric G proteins can bind to both the N-terminal and C-terminal domains of G-protein-activated inwardly rectifying K+ channels (GIRKs) to inhibit their activities. In Arabidopsis guard cells, the Gα subunit GPA1 mediates multiple stimuli-regulated stomatal movements via inhibiting guard cell inward-rectifying K+ (K+in) current, but it remains unclear whether GPA1 directly interacts with and inhibits the activities of K+in channels. Here, we found that GPA1 interacted with the transmembrane domain rather than the intracellular domain of the Shaker family K+in channel KAT1. Two-Electrode Voltage-Clamp experiments in Xenopus oocytes demonstrated that GPA1 significantly inhibited KAT1 channel activity. However, GPA1 could not inhibit the assembly of KAT1 as well as KAT2 as homo- and hetero-tetramers and alter the subcellular localization and protein stability of these channels. In conclusion, these findings reveal a novel regulatory mechanism for Gα inhibition of the Shaker family K+in channel KAT1 via binding to its channel transmembrane domains but without affecting its subcellular localization, protein stability and the formation of functional homo- and hetero-tetramers. This suggests that in both animal and plant cells, Gα can regulate K+in channels through physical interaction, albeit with differing mechanisms of interaction and regulation. •The G protein α subunit GPA1 in Arabidopsis can bind to the transmembrane domain of the inward rectifying potassium channel KAT1 and inhibit its channel activity without affecting its subcellular localization, protein stability or assembly as homo- or hetero-tetramers.