Enhanced trafficking of tetrameric Kv4.3 channels by KChIP1 clamping.
The cytoplamsic auxiliary KChIPs modulate surface expression and gating properties of Kv4 channels. Recent co-crystal structure of Kv4.3 N-terminus and KChIP1 reveals a clamping action of the complex in which a single KChIP1 molecule laterally binds two neighboring Kv4.3 N-termini at different locations, thus forming two contact interfaces involved in the protein-protein interaction. In the second interface, it functions to stabilize the tetrameric assembly, but the role it plays in channel trafficking remains elusive. In this study, we examined the effects of KChIP1 on Kv4 protein trafficking in COS-7 cells expressing EGFP-tagged Kv4.3 channels using confocal microscopy. Mutations either in KChIP1 (KChIP1 L39E-Y57A-K61A) or Kv4.3 (Kv4.3 E70A-F73E) that disrupt the protein-protein interaction within the second interface can reduce surface expression of Kv4 channel proteins. Kv4.3 C110A, the Zn2+ binding site mutation in T1 domain, that disrupts the tetrameric assembly of the channels can be rescued by WT KChIP1, but not the KChIP1 triple mutant. These results were further confirmed by whole cell current recordings in oocytes. Our findings show that key residues of second interface involved in stabilizing tetrameric assembly can regulate the channel trafficking, indicating an intrinsic link between tetrameric assembly and channel trafficking. The results also suggest that formation of octameric Kv4 and KChIP complex by KChIPs clamping takes place before their trafficking to final destination on the cell surface.
Cui
Yuan Yuan
YY
Neuroscience Research Institute and Department of Neurobiology, Key Laboratory for Neuroscience of the Ministry of Education, Center for Protein Sciences, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100083, China.
Liang
Ping
P
Wang
Ke Wei
KW
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D051605:Kv Channel-Interacting Proteins / Q000235:genetics / Q000502:physiology*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D025941:Protein Interaction Mapping; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D051672:Shal Potassium Channels / Q000235:genetics / Q000502:physiology*; D014981:Xenopus
D051605:Kv Channel-Interacting Proteins; D051672:Shal Potassium Channels