C-terminal interaction of KCNQ2 and KCNQ3 K+ channels.
Coexpression of KCNQ2 and KCNQ3 channels results in a 10-fold increased current amplitude compared to that of KCNQ2 alone, suggesting the formation of heteromultimeric channels. There is no interaction of either channel with KCNQ1. We evaluated the C-terminus as a potential interaction domain by construction of chimeras with interchanged C-termini of KCNQ1, KCNQ2 and KCNQ3 and functional expression in Xenopus oocytes. The chimera of KCNQ1 with a KCNQ2 C-terminus (Q1ctQ2) showed an 8-fold increase in current amplitude, and Q1ctQ3 a 3-fold increase when coexpressed with KCNQ3 and KCNQ2, respectively, indicating that the C-terminus contains an interaction domain. To characterize this interacting region, we studied further chimeras of KCNQ1 containing different parts of the KCNQ3 C-terminus for interaction with KCNQ2. We also evaluated short sequences of the KCNQ2 C-terminus for a dominant-negative effect on Q1ctQ3. According to the results of these experiments, functional interaction of KCNQ2 and KCNQ3 requires a highly conserved region of about 80 amino acids, previously called the A-domain, plus either 40 residues downstream of the A-domain (B-domain) or the proximal C-terminus between S6 and the A-domain. Furthermore, the chimeras Q1ctQ3 and Q2ctQ3 showed > 10-fold increased current amplitudes compared to KCNQ1 or KCNQ2 alone and a strong depolarizing shift of voltage-dependent activation. The proximal part of the KCNQ3 C-terminus was necessary to produce these effects. Our results indicate that specific parts of the C-terminus enable the interaction between KCNQ2 and KCNQ3 channels and that different parts of the KCNQ3 C-terminus are important for regulating current amplitude.
Maljevic
Snezana
S
Department of Applied Physiology, University of Ulm, Germany.
Lerche
Christian
C
Seebohm
Guiscard
G
Alekov
Alexi K
AK
Busch
Andreas E
AE
Lerche
Holger
H
D000595:Amino Acid Sequence; D000818:Animals; D004594:Electrophysiology; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D051658:KCNQ2 Potassium Channel; D051659:KCNQ3 Potassium Channel; D008564:Membrane Potentials / Q000502:physiology; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014982:Xenopus laevis
D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human; D051659:KCNQ3 Potassium Channel; C496916:KCNQ3 protein, human; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins