Enhanced Trafficking of Tetrameric Kv4.3 Channels by KChIP1 Clamping |
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Authors: | Yuan Yuan Cui Ping Liang Ke Wei Wang |
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Institution: | (1) 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 |
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Abstract: | 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.
Special issue article in honor of Dr. Ji-Sheng Han. |
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Keywords: | KChIP1 Kv4 3 T1 zinc binding site Trafficking Tetrameric assembly |
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