title: The Eag domain regulates the voltage-dependent inactivation of rat Eag1 K+ channels.
abstract: Eag (Kv10) and Erg (Kv11) belong to two distinct subfamilies of the ether-à-go-go K+ channel family (KCNH). While Erg channels are characterized by an inward-rectifying current-voltage relationship that results from a C-type inactivation, mammalian Eag channels display little or no voltage-dependent inactivation. Although the amino (N)-terminal region such as the eag domain is not required for the C-type inactivation of Erg channels, an N-terminal deletion in mouse Eag1 has been shown to produce a voltage-dependent inactivation. To further discern the role of the eag domain in the inactivation of Eag1 channels, we generated N-terminal chimeras between rat Eag (rEag1) and human Erg (hERG1) channels that involved swapping the eag domain alone or the complete cytoplasmic N-terminal region. Functional analyses indicated that introduction of the homologous hERG1 eag domain led to both a fast phase and a slow phase of channel inactivation in the rEag1 chimeras. By contrast, the inactivation features were retained in the reverse hERG1 chimeras. Furthermore, an eag domain-lacking rEag1 deletion mutant also showed the fast phase of inactivation that was notably attenuated upon co-expression with the rEag1 eag domain fragment, but not with the hERG1 eag domain fragment. Additionally, we have identified a point mutation in the S4-S5 linker region of rEag1 that resulted in a similar inactivation phenotype. Biophysical analyses of these mutant constructs suggested that the inactivation gating of rEag1 was distinctly different from that of hERG1. Overall, our findings are consistent with the notion that the eag domain plays a critical role in regulating the inactivation gating of rEag1. We propose that the eag domain may destabilize or mask an inherent voltage-dependent inactivation of rEag1 K+ channels.
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ting-Feng
authors.initials: TF
authors.lastname: Lin
authors.affiliation: School of Medicine, Fu-Jen Catholic University, Hsin-Chuang, New Taipei City, Taiwan.
authors.forename: Guey-Mei
authors.initials: GM
authors.lastname: Jow
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hsin-Yu
authors.initials: HY
authors.lastname: Fang
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ssu-Ju
authors.initials: SJ
authors.lastname: Fu
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hao-Han
authors.initials: HH
authors.lastname: Wu
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Mei-Miao
authors.initials: MM
authors.lastname: Chiu
authors.affiliation: Institute of Anatomy and Cell Biology, School of Medicine, National Yang-Ming University, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Chung-Jiuan
authors.initials: CJ
authors.lastname: Jeng
mesh_terms: D000818:Animals; D051638:Ether-A-Go-Go Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D051379:Mice; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary; D018075:RNA, Complementary / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014162:Transfection; D014981:Xenopus / Q000254:growth & development
chemical_list: D051638:Ether-A-Go-Go Potassium Channels; D018075:RNA, Complementary; D011993:Recombinant Fusion Proteins