title: A new interaction between proximal and distal C-terminus of Cav1.2 channels.
abstract: Cardiac Cav1.2 channels, coupling membrane stimulation to intracellular Ca2+signaling, are regulated by multiple cytoplasmic factors, such as calmodulin (CaM), phosphorylation, Ca2+, ATP and intramolecular fragments of the channel. The interaction between distal and proximal C-terminal regulatory domains (DCRD and PCRD) of Cav1.2 channel is suggested to inhibit the channel activity, while PKA-mediated phosphorylation facilitates Cav1.2 channel by releasing such an interaction. Here, we report that the interaction between the distal C-terminus (CT3) and the proximal C-terminus (CT1) are inhibited by CaM in a Ca2+-dependent manner. Furthermore, CT3D (a short CT3 with DCRD truncated) interacts with CT1B (a short CT1 with EF-hand and PCRD truncated), revealing a new interaction between distal and proximal C-terminus. Ca2+/CaM inhibited the binding of CT3D to CT1B more strongly than the binding between CT3 and CT1, implying that the interaction of DCRD/PCRD (in CT3/CT1) might cooperate with the binding of CT3D to CT1B. We name the new CT1B-binding region of CT3D as CaM-competitive domain (CCD). The electrophysiological experiments show that CT3D inhibits while CT1B facilitates Cav1.2 channel activity in inside-out patches in guinea-pig ventricular myocytes. These results suggest that distal C-terminus inhibits Cav1.2 channel through modulation of the CaM-binding property of the channels.
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan; Department of Chemical Engineering, School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110004, China.
authors.forename: Liting
authors.initials: L
authors.lastname: Lyu
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Gao
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan. Electronic address: jjxuk@m3.kufm.kagoshima-u.ac.jp.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Minobe
authors.affiliation: Department of Chemical Engineering, School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110004, China. Electronic address: ztkagoshima@yahoo.co.jp.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism / Q000502:physiology; D055724:Electrophysiological Phenomena; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D032383:Myocytes, Cardiac / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding; D000072417:Protein Domains / Q000502:physiology
chemical_list: D020746:Calcium Channels, L-Type; D002147:Calmodulin; D002118:Calcium
keywords: Calmodulin; Cardiac myocytes; Cav1.2; Patch clamp; Pull-down assay