title: Reciprocal control of hERG stability by Hsp70 and Hsc70 with implication for restoration of LQT2 mutant stability.
abstract: BACKGROUND
  The human ether-a-go-go-related gene (hERG) encodes the α subunit of the potassium current I(Kr). It is highly expressed in cardiomyocytes and its mutations cause long QT syndrome type 2. Heat shock protein (Hsp)70 is known to promote maturation of hERG. Hsp70 and heat shock cognate (Hsc70) 70 has been suggested to play a similar function. However, Hsc70 has recently been reported to counteract Hsp70.
  
  
  OBJECTIVE
  We investigated whether Hsc70 counteracts Hsp70 in the control of wild-type and mutant hERG stability.
  
  
  RESULTS
  Coexpression of Hsp70 with hERG in HEK293 cells suppressed hERG ubiquitination and increased the levels of both immature and mature forms of hERG. Immunocytochemistry revealed increased levels of hERG in the endoplasmic reticulum and on the cell surface. Electrophysiological studies showed increased I(Kr). All these effects of Hsp70 were abolished by Hsc70 coexpression. Heat shock treatment of HL-1 mouse cardiomyocytes induced endogenous Hsp70, switched mouse ERG associated with Hsc70 to Hsp70, increased I(Kr), and shortened action potential duration. Channels with disease-causing missense mutations in intracellular domains had a higher binding capacity to Hsc70 than wild-type channels and channels with mutations in the pore region. Knockdown of Hsc70 by small interfering RNA or heat shock prevented degradation of mutant hERG proteins with mutations in intracellular domains.
  
  
  CONCLUSIONS
  These results indicate reciprocal control of hERG stability by Hsp70 and Hsc70. Hsc70 is a potential target in the treatment of LQT2 resulting from missense hERG mutations.
authors.affiliation: Department of Genetic Medicine and Regenerative Therapeutics, Institute of Regenerative Medicine and Biofunction, Tottori University, Japan.
authors.forename: Peili
authors.initials: P
authors.lastname: Li
authors.forename: Haruaki
authors.initials: H
authors.lastname: Ninomiya
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kurata
authors.forename: Masaru
authors.initials: M
authors.lastname: Kato
authors.forename: Junichiro
authors.initials: J
authors.lastname: Miake
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Igawa
authors.forename: Akira
authors.initials: A
authors.lastname: Nakai
authors.forename: Katsumi
authors.initials: K
authors.lastname: Higaki
authors.forename: Futoshi
authors.initials: F
authors.lastname: Toyoda
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Minoru
authors.initials: M
authors.lastname: Horie
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsuura
authors.forename: Akio
authors.initials: A
authors.lastname: Yoshida
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Shirayoshi
authors.forename: Masayasu
authors.initials: M
authors.lastname: Hiraoka
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D004721:Endoplasmic Reticulum / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D057809:HEK293 Cells; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D020125:Mutation, Missense / Q000235:genetics*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: D051638:Ether-A-Go-Go Potassium Channels; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D034741:RNA, Small Interfering