title: Transgenic expression of beta-APP in fast-twitch skeletal muscle leads to calcium dyshomeostasis and IBM-like pathology.
abstract: Intracellular deposition of the beta-amyloid (Abeta) peptide is an increasingly recognized pathological hallmark associated with neurodegeneration and muscle wasting in Alzheimer's disease (AD) and inclusion body myositis (IBM), respectively. Previous reports have implicated dysregulation of beta-amyloid precursor protein (betaAPP) expression in IBM. Accumulation of full-length betaAPP, its various proteolytic derivatives including Abeta, and phospho-tau into vacuolated inclusions is an early pathogenic event. We previously reported on a statistical tendency favoring fast twitch fiber involvement in IBM, reminiscent of the tissue specific patterns of misfolded protein deposition seen in neurodegenerative diseases. To test this principle, we generated an animal model in which human wild-type (WT) betaAPP expression was limited to postnatal type II skeletal muscle. Hemizygous transgenic mice harboring increased levels of holo betaAPP751 and Abeta in skeletal muscle fibers became significantly weaker with age compared with nontransgenic littermates and exhibited typical myopathic features. A subpopulation of dissociated muscle fibers from transgenic mice exhibited a 2-fold increase in resting calcium and membrane depolarization compared with nontransgenic littermates. Taken together, these data indicate that overexpression of human betaAPP in fast twitch skeletal muscle of transgenic mice is sufficient for the development of some features characteristic of IBM, including abnormal tau histochemistry. The increase in resting calcium and depolarization are novel findings, suggesting both a mechanism for the weakness and an avenue for therapeutic intervention in IBM.
authors.affiliation: Department of Neurology, Caritas St. Elizabeth's Medical Center of Boston, Tufts University School of Medicine, 736 Cambridge St., Boston, MA, USA.
authors.forename: Charbel E-H
authors.initials: CE
authors.lastname: Moussa
authors.forename: Qinghao
authors.initials: Q
authors.lastname: Fu
authors.forename: Pravir
authors.initials: P
authors.lastname: Kumar
authors.forename: Alexander
authors.initials: A
authors.lastname: Shtifman
authors.forename: Jose R
authors.initials: JR
authors.lastname: Lopez
authors.forename: Paul D
authors.initials: PD
authors.lastname: Allen
authors.forename: Frank
authors.initials: F
authors.lastname: LaFerla
authors.forename: David
authors.initials: D
authors.lastname: Weinberg
authors.forename: Jordi
authors.initials: J
authors.lastname: Magrane
authors.forename: Tamar
authors.initials: T
authors.lastname: Aprahamian
authors.forename: Kenneth
authors.initials: K
authors.lastname: Walsh
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Rosen
authors.forename: Henry W
authors.initials: HW
authors.lastname: Querfurth
mesh_terms: D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008822:Mice, Transgenic; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000378:metabolism; D018979:Myositis, Inclusion Body / Q000473:pathology*; D014018:Tissue Distribution
chemical_list: D016564:Amyloid beta-Protein Precursor; D002118:Calcium