title: Silencing of desmoplakin decreases connexin43/Nav1.5 expression and sodium current in HL‑1 cardiomyocytes.
abstract: Desmosomes and gap junctions are situated in the intercalated disks of cardiac muscle and maintain the integrity of mechanical coupling and electrical impulse conduction between cells. The desmosomal plakin protein, desmoplakin (DSP), also plays a crucial role in the stability of these interconnected components as well as gap junction connexin proteins. In addition to cell‑to‑cell junctions, other molecules, including voltage‑gated sodium channels (Nav1.5) are present in the intercalated disk and support the contraction of cardiac muscle. Mutations in genes encoding desmosome proteins may result in fatal arrhythmias, including arrhythmogenic right ventricular cardiomyopathy (ARVC). Therefore, the aim of the present study was to determine whether the presence of DSP is necessary for the normal function and localization of gap junction protein connexin43 (Cx43) and Nav1.5. To examine this hypothesis, RNA interference was utilized to knock down the expression of DSP in HL‑1 cells and the content, distribution and function of Cx43 and Nav1.5 was assessed. Western blotting and flow cytometry experiments revealed that Cx43 and Nav1.5 expression decreased following DSP silencing. In addition, immunofluorescence studies demonstrated that a loss of DSP expression led to an abnormal distribution of Cx43 and Nav1.5, while scrape‑loading dye/transfer revealed a decrease in dye transfer in DSP siRNA‑treated cells. The sodium current was also recorded by the whole‑cell patch clamp technique. The results indicated that DSP suppression decreased sodium current and slowed conduction velocity in cultured cells. The present study indicates that impaired mechanical coupling largely affects electrical synchrony, further uncovering the pathogenesis of ARVC.
authors.affiliation: Department of Cardiology, Guangdong Cardiovascular Institute, Guangzhou, Guangdong 510080, P.R. China.
authors.forename: Qianhuan
authors.initials: Q
authors.lastname: Zhang
authors.forename: Chunyu
authors.initials: C
authors.lastname: Deng
authors.forename: Fang
authors.initials: F
authors.lastname: Rao
authors.forename: Rohan M
authors.initials: RM
authors.lastname: Modi
authors.forename: Jiening
authors.initials: J
authors.lastname: Zhu
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Liu
authors.forename: Liping
authors.initials: L
authors.lastname: Mai
authors.forename: Honghong
authors.initials: H
authors.lastname: Tan
authors.forename: Xiyong
authors.initials: X
authors.lastname: Yu
authors.forename: Qiuxiong
authors.initials: Q
authors.lastname: Lin
authors.forename: Dingzhang
authors.initials: D
authors.lastname: Xiao
authors.forename: Sujuan
authors.initials: S
authors.lastname: Kuang
authors.forename: Shulin
authors.initials: S
authors.lastname: Wu
mesh_terms: D000818:Animals; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism*; D051180:Desmoplakins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology; D008564:Membrane Potentials; D051379:Mice; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D051180:Desmoplakins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D034741:RNA, Small Interfering; C568321:Scn5a protein, mouse; D012964:Sodium