A highly prevalent equine glycogen storage disease is explained by constitutive activation of a mutant glycogen synthase
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Standard
A highly prevalent equine glycogen storage disease is explained by constitutive activation of a mutant glycogen synthase. / Maile, C A; Hingst, Janne Rasmuss; Mahalingan, K K; O'Reilly, A O; Cleasby, Mark E; Mickelson, James R; McCue, M E; Anderson, S M; Hurley, T D; Wojtaszewski, Jørgen; Piercy, R J.
I: B B A - General Subjects, Bind 1861, Nr. 1, Part A, 2017, s. 3388-3398.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - A highly prevalent equine glycogen storage disease is explained by constitutive activation of a mutant glycogen synthase
AU - Maile, C A
AU - Hingst, Janne Rasmuss
AU - Mahalingan, K K
AU - O'Reilly, A O
AU - Cleasby, Mark E
AU - Mickelson, James R
AU - McCue, M E
AU - Anderson, S M
AU - Hurley, T D
AU - Wojtaszewski, Jørgen
AU - Piercy, R J
N1 - CURIS 2017 NEXS 013
PY - 2017
Y1 - 2017
N2 - BACKGROUND: Equine type 1 polysaccharide storage myopathy (PSSM1) is associated with a missense mutation (R309H) in the glycogen synthase (GYS1) gene, enhanced glycogen synthase (GS) activity and excessive glycogen and amylopectate inclusions in muscle.METHODS: Equine muscle biochemical and recombinant enzyme kinetic assays in vitro and homology modelling in silico, were used to investigate the hypothesis that higher GS activity in affected horse muscle is caused by higher GS expression, dysregulation, or constitutive activation via a conformational change.RESULTS: PSSM1-affected horse muscle had significantly higher glycogen content than control horse muscle despite no difference in GS expression. GS activity was significantly higher in muscle from homozygous mutants than from heterozygote and control horses, in the absence and presence of the allosteric regulator, glucose 6 phosphate (G6P). Muscle from homozygous mutant horses also had significantly increased GS phosphorylation at sites 2+2a and significantly higher AMPKα1 (an upstream kinase) expression than controls, likely reflecting a physiological attempt to reduce GS enzyme activity. Recombinant mutant GS was highly active with a considerably lower Km for UDP-glucose, in the presence and absence of G6P, when compared to wild type GS, and despite its phosphorylation.CONCLUSIONS: Elevated activity of the mutant enzyme is associated with ineffective regulation via phosphorylation rendering it constitutively active. Modelling suggested that the mutation disrupts a salt bridge that normally stabilises the basal state, shifting the equilibrium to the enzyme's active state.GENERAL SIGNIFICANCE: This study explains the gain of function pathogenesis in this highly prevalent polyglucosan myopathy.
AB - BACKGROUND: Equine type 1 polysaccharide storage myopathy (PSSM1) is associated with a missense mutation (R309H) in the glycogen synthase (GYS1) gene, enhanced glycogen synthase (GS) activity and excessive glycogen and amylopectate inclusions in muscle.METHODS: Equine muscle biochemical and recombinant enzyme kinetic assays in vitro and homology modelling in silico, were used to investigate the hypothesis that higher GS activity in affected horse muscle is caused by higher GS expression, dysregulation, or constitutive activation via a conformational change.RESULTS: PSSM1-affected horse muscle had significantly higher glycogen content than control horse muscle despite no difference in GS expression. GS activity was significantly higher in muscle from homozygous mutants than from heterozygote and control horses, in the absence and presence of the allosteric regulator, glucose 6 phosphate (G6P). Muscle from homozygous mutant horses also had significantly increased GS phosphorylation at sites 2+2a and significantly higher AMPKα1 (an upstream kinase) expression than controls, likely reflecting a physiological attempt to reduce GS enzyme activity. Recombinant mutant GS was highly active with a considerably lower Km for UDP-glucose, in the presence and absence of G6P, when compared to wild type GS, and despite its phosphorylation.CONCLUSIONS: Elevated activity of the mutant enzyme is associated with ineffective regulation via phosphorylation rendering it constitutively active. Modelling suggested that the mutation disrupts a salt bridge that normally stabilises the basal state, shifting the equilibrium to the enzyme's active state.GENERAL SIGNIFICANCE: This study explains the gain of function pathogenesis in this highly prevalent polyglucosan myopathy.
KW - Faculty of Science
KW - PSSM1
KW - Polyglucosan
KW - Glycogen synthase
KW - Glycogen
KW - Muscle
KW - Glycogen storage disease
U2 - 10.1016/j.bbagen.2016.08.021
DO - 10.1016/j.bbagen.2016.08.021
M3 - Journal article
C2 - 27592162
VL - 1861
SP - 3388
EP - 3398
JO - B B A - General Subjects
JF - B B A - General Subjects
SN - 0304-4165
IS - 1, Part A
ER -
ID: 165710917