title: Modeling oculopharyngeal muscular dystrophy in myotube cultures reveals reduced accumulation of soluble mutant PABPN1 protein.
abstract: Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant disease caused by an alanine tract expansion mutation in poly(A) binding protein nuclear 1 (expPABPN1). To model OPMD in a myogenic and physiological context, we generated mouse myoblast cell clones stably expressing either human wild type (WT) or expPABPN1 at low levels. Transgene expression is induced on myotube differentiation and results in formation of insoluble nuclear PABPN1 aggregates that are similar to those observed in patients with OPMD. Quantitative analysis of PABPN1 in myotube cultures revealed that expPABPN1 accumulation and aggregation is greater than that of the WT protein. We found that aggregation of expPABPN1 is more affected than WT PABPN1 by inhibition of proteasome activity. Consistent with this, in myotube cultures expressing expPABPN1, deregulation of the proteasome was identified as the most significantly perturbed pathway. Differences in the accumulation of soluble WT and expPABPN1 were consistent with differences in ubiquitination and rate of protein turnover. This study demonstrates, for the first time to our knowledge, that, in myotubes, the ratio of soluble/insoluble expPABPN1 is significantly lower compared with that of the WT protein. We suggest that this difference can contribute to muscle weakness in OPMD.
authors.affiliation: Center for Human and Clinical Genetics, Leiden University Medical Center, Leiden, the Netherlands. v.raz@lumc.nl
authors.forename: Vered
authors.initials: V
authors.lastname: Raz
authors.forename: Samantha
authors.initials: S
authors.lastname: Routledge
authors.forename: Andrea
authors.initials: A
authors.lastname: Venema
authors.forename: Hellen
authors.initials: H
authors.lastname: Buijze
authors.forename: Erik
authors.initials: E
authors.lastname: van der Wal
authors.forename: Seyedyahya
authors.initials: S
authors.lastname: Anvar
authors.forename: Kirsten R
authors.initials: KR
authors.lastname: Straasheijm
authors.forename: Rinse
authors.initials: R
authors.lastname: Klooster
authors.forename: Michael
authors.initials: M
authors.lastname: Antoniou
authors.forename: Silvère M
authors.initials: SM
authors.lastname: van der Maarel
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003893:Desmin / Q000235:genetics; D004195:Disease Models, Animal; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology*; D009132:Muscles / Q000473:pathology; D039141:Muscular Dystrophy, Oculopharyngeal / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism*; D039103:Poly(A)-Binding Protein II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025821:Polyubiquitin / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D020836:Protein Structure, Quaternary; D015398:Signal Transduction; D012995:Solubility; D059467:Transcriptome; D014162:Transfection; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D054875:Ubiquitination
chemical_list: D003893:Desmin; D050505:Mutant Proteins; D039103:Poly(A)-Binding Protein II; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex