On noxious desmin: functional effects of a novel heterozygous desmin insertion mutation on the extrasarcomeric desmin cytoskeleton and mitochondria.
Recent studies in desmin (-/-) mice have shown that the targeted ablation of desmin leads to pathological changes of the extrasarcomeric intermediate filament cytoskeleton, as well as structural and functional abnormalities of mitochondria in striated muscle. Here, we report on a novel heterozygous single adenine insertion mutation (c.5141_5143insA) in a 40-year-old patient with a distal myopathy. The insertion mutation leads to a frameshift and a truncated desmin (K239fs242). Using transfection studies in SW13 and BHK21 cells, we show that the K239fsX242 desmin mutant is incapable of forming a desmin intermediate filament network. Furthermore, it induces the collapse of a pre-existing desmin cytoskeleton, alters the subcellular distribution of mitochondria and leads to abnormal cytoplasmic protein aggregates reminiscent of desmin-immunoreactive granulofilamentous material seen in the ultrastructural analysis of the patient's muscle. Analysis of mitochondrial function in isolated saponin-permeablized skeletal muscle fibres from our patient showed decreased maximal rates of respiration with the NAD-dependent substrate combination glutamate and malate, as well as a higher amytal sensitivity of respiration, indicating an in vivo inhibition of complex I activity. Our findings suggest that the heterozygous K239fsX242 desmin insertion mutation has a dominant negative effect on the polymerization process of desmin intermediate filaments and affects not only the subcellular distribution, but also biochemical properties of mitochondria in diseased human skeletal muscle. As a consequence, the intermediate filament pathology-induced mitochondrial dysfunction may contribute to the degeneration/regeneration process leading to progressive muscle dysfunction in human desminopathies.
Schröder
Rolf
R
Department of Neurology, University Hospital Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. rolf.schroeder@ikb.uni-bonn.de
Goudeau
Bertrand
B
Simon
Monique Casteras
MC
Fischer
Dirk
D
Eggermann
Thomas
T
Clemen
Christoph S
CS
Li
Zhenlin
Z
Reimann
Jens
J
Xue
Zhigang
Z
Rudnik-Schöneborn
Sabine
S
Zerres
Klaus
K
van der Ven
Peter F M
PF
Fürst
Dieter O
DO
Kunz
Wolfram S
WS
Vicart
Patrick
P
D000225:Adenine / Q000737:chemistry; D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D018076:DNA, Complementary / Q000378:metabolism; D003893:Desmin / Q000235:genetics* / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D016368:Frameshift Mutation; D005799:Genes, Dominant; D006579:Heterozygote; D006801:Humans; D008297:Male; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009243:NAD / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014162:Transfection
D018076:DNA, Complementary; D003893:Desmin; D009243:NAD; D004247:DNA; D000225:Adenine