Cystamine suppresses polyalanine toxicity in a mouse model of oculopharyngeal muscular dystrophy.
Oculopharyngeal muscular dystrophy (OPMD) is caused by a trinucleotide repeat expansion mutation in the coding region of the gene encoding PABPN1 (polyadenylate-binding protein nuclear 1). Mutant PABPN1 with a polyalanine tract expansion forms aggregates within the nuclei of skeletal muscle fibers. There is currently no effective treatment. We have developed cell and mouse models of OPMD and have identified the aggregation of mutant PABPN1 and apoptosis as therapeutic targets. Here, we show that transglutaminase activity is increased in muscle from OPMD model mice. Elevated transglutaminase 2 expression enhances, whereas TG2 knockdown suppresses, the toxicity and aggregation of mutant PABPN1 in cells. Cystamine protects against the toxicity of mutant PABPN1 and exerts its effect via the inhibition of transglutaminase 2, as cystamine treatment is unable to further reduce the protective effect of transglutaminase 2 knockdown on mutant PABPN1 toxicity in cells. Cystamine also reduces the aggregation and toxicity of mutant PABPN1 in human cells. In a mouse model of OPMD, cystamine treatment reduced the elevated transglutaminase activity, attenuated muscle weakness, reduced aggregate load, and decreased apoptotic markers in muscle. Therefore, inhibitors of transglutaminase 2 should be considered as possible therapeutics for OPMD.
Department of Medical Genetics, University of Cambridge, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, UK.
Janet E
JE
Davies
Claudia
C
Rose
Sovan
S
Sarkar
David C
DC
Rubinsztein
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism; D002460:Cell Line; D003538:Cystamine / Q000494:pharmacology / Q000627:therapeutic use*; D019610:Cytoprotection / Q000187:drug effects; D004195:Disease Models, Animal; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D018908:Muscle Weakness / Q000188:drug therapy; D039141:Muscular Dystrophy, Oculopharyngeal / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D010455:Peptides / Q000235:genetics*; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019680:Trinucleotide Repeat Expansion / Q000187:drug effects / Q000235:genetics*
D015415:Biomarkers; D010455:Peptides; C019529:polyalanine; D011503:Transglutaminases; D003538:Cystamine