title: Functional diversity of voltage-sensing phosphatases in two urodele amphibians.
abstract: Voltage-sensing phosphatases (VSPs) share the molecular architecture of the voltage sensor domain (VSD) with voltage-gated ion channels and the phosphoinositide phosphatase region with the phosphatase and tensin homolog (PTEN), respectively. VSPs enzymatic activities are regulated by the motions of VSD upon depolarization. The physiological role of these proteins has remained elusive, and insights may be gained by investigating biological variations in different animal species. Urodele amphibians are vertebrates with potent activities of regeneration and also show diverse mechanisms of polyspermy prevention. We cloned cDNAs of VSPs from the testes of two urodeles; Hynobius nebulosus and Cynops pyrrhogaster, and compared their expression and voltage-dependent activation. Their molecular architecture is highly conserved in both Hynobius VSP (Hn-VSP) and Cynops VSP (Cp-VSP), including the positively-charged arginine residues in the S4 segment of the VSD and the enzymatic active site for substrate binding, yet the C-terminal C2 domain of Hn-VSP is significantly shorter than that of Cp-VSP and other VSP orthologs. RT-PCR analysis showed that gene expression pattern was distinct between two VSPs. The voltage sensor motions and voltage-dependent phosphatase activities were investigated electrophysiologically by expression in Xenopus oocytes. Both VSPs showed "sensing" currents, indicating that their voltage sensor domains are functional. The phosphatase activity of Cp-VSP was found to be voltage dependent, as shown by its ability to regulate the conductance of coexpressed GIRK2 channels, but Hn-VSP lacked such phosphatase activity due to the truncation of its C2 domain.
authors.affiliation: Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
authors.forename: Joshua
authors.initials: J
authors.lastname: Mutua
authors.affiliation: Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Jinno
authors.affiliation: Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Souhei
authors.initials: S
authors.lastname: Sakata
authors.affiliation: Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Okochi
authors.affiliation: Laboratory of Molecular Developmental Biology, Department of Applied Molecular Biosciences, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ueno
authors.affiliation: Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Tsutsui
authors.affiliation: Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kawai
authors.affiliation: Laboratory of Molecular Developmental Biology, Department of Applied Molecular Biosciences, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Iwao
authors.affiliation: Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okamura
keywords: C2 domain; phosphoinositides; testis; voltage‐sensing phosphatase