title: HSPB1, HSPB6, HSPB7 and HSPB8 protect against RhoA GTPase-induced remodeling in tachypaced atrial myocytes.
abstract: BACKGROUND
  We previously demonstrated the small heat shock protein, HSPB1, to prevent tachycardia remodeling in in vitro and in vivo models for Atrial Fibrillation (AF). To gain insight into its mechanism of action, we examined the protective effect of all 10 members of the HSPB family on tachycardia remodeling. Furthermore, modulating effects of HSPB on RhoA GTPase activity and F-actin stress fiber formation were examined, as this pathway was found of prime importance in tachycardia remodeling events and the initiation of AF.
  
  
  RESULTS
  Tachypacing (4 Hz) of HL-1 atrial myocytes significantly and progressively reduced the amplitude of Ca²⁺ transients (CaT). In addition to HSPB1, also overexpression of HSPB6, HSPB7 and HSPB8 protected against tachypacing-induced CaT reduction. The protective effect was independent of HSPB1. Moreover, tachypacing induced RhoA GTPase activity and caused F-actin stress fiber formation. The ROCK inhibitor Y27632 significantly prevented tachypacing-induced F-actin formation and CaT reductions, showing that RhoA activation is required for remodeling. Although all protective HSPB members prevented the formation of F-actin stress fibers, their mode of action differs. Whilst HSPB1, HSPB6 and HSPB7 acted via direct prevention of F-actin formation, HSPB8-protection was mediated via inhibition of RhoA GTPase activity.
  
  
  CONCLUSIONS
  Overexpression of HSPB1, as well as HSPB6, HSPB7 and HSPB8 independently protect against tachycardia remodeling by attenuation of the RhoA GTPase pathway at different levels. The cardioprotective role for multiple HSPB members indicate a possible therapeutic benefit of compounds able to boost the expression of single or multiple members of the HSPB family.
authors: Department of Radiation and Stress Cell Biology, University Institute for Drug Exploration (GUIDE), University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors: Lei
authors: L
authors: Ke
authors: Roelien A M
authors: RA
authors: Meijering
authors: Femke
authors: F
authors: Hoogstra-Berends
authors: Katarina
authors: K
authors: Mackovicova
authors: Michel J
authors: MJ
authors: Vos
authors: Isabelle C
authors: IC
authors: Van Gelder
authors: Robert H
authors: RH
authors: Henning
authors: Harm H
authors: HH
authors: Kampinga
authors: Bianca J J M
authors: BJ
authors: Brundel
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D020013:Calcium Signaling; D002316:Cardiotonic Agents / Q000378:metabolism; D004789:Enzyme Activation; D006325:Heart Atria / Q000473:pathology*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D032383:Myocytes, Cardiac / Q000201:enzymology*; D058105:Polymerization; D022502:Stress Fibers / Q000378:metabolism; D013610:Tachycardia / Q000201:enzymology / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D002316:Cardiotonic Agents; D006360:Heat-Shock Proteins; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein