Impairment of cell cycle in myotonic dystrophy

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 14570785
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Pediatrics
• Research Institution: Kurume University
• Principal Investigator: NAGAMITSU Shinichiro Kurume University of Medicine, Instructor, 医学部, 助手 (30258454)
• Project Period (FY): 2002 – 2004
• Keywords: DMPK / binding protein / ubiquilin-1 / MYPT1 / kinase assay

Research Abstract

Myotonic dystrophy type I is an autosomal dominant disease with multisystemic phenotype, which is caused by an expansion of the unstable CTG repeat in the uryotonic dystrophy protein kinase (DMPK) gene. Although the mutant DMPK mRNA containing an expanded CUG repeat appears to play a major role in the pathogenic mechanism, recent studies of DMPK deficient mice suggested that the DMPK protein also contribute to the cardiac and skeletal muscle phenotype of DM1. DMPK is a serine-threonine kinase that may regulate the myosin light chain function by phosphorylating the myosin binding subunit of myosin phosphatase (MYPT1). We have identified an ubiquitin-like protein, ubiquilin-I, as a DMPK- interacting protein by yeast two-hybrid screening, pull-down assays, and immunocyotological colocalization, and demonstrated that the Stil-like repeat element domain of ubiquilin-1 is required to bind to the kinase domain of DMPK. DMPK did not phosphorylate ubiquilin-1 ; however, equimolar or lower concentrations of ubiquilin-1 increased phosphorylation of the MYPT-1 regulatory site peptide by DMPK two to four-fold. The half-life of DMPK was increased from 41 hours to 73 hours by ubiquilin-1 co-transfection, suggesting that ubiquilin-1 inhibits the degradation of DMPK. Our results indicate that ubiquilin-1 interacts with DMPK and modulates the kinase activity and degradation of DMPK.