title: Coiled-coil interactions modulate multimerization, mitochondrial binding and kinase activity of myotonic dystrophy protein kinase splice isoforms.
abstract: The myotonic dystrophy protein kinase polypeptide repertoire in mice and humans consists of six different splice isoforms that vary in the nature of their C-terminal tails and in the presence or absence of an internal Val-Ser-Gly-Gly-Gly motif. Here, we demonstrate that myotonic dystrophy protein kinase isoforms exist in high-molecular-weight complexes controlled by homo- and heteromultimerization. This multimerization is mediated by coiled-coil interactions in the tail-proximal domain and occurs independently of alternatively spliced protein segments or myotonic dystrophy protein kinase activity. Complex formation was impaired in myotonic dystrophy protein kinase mutants in which three leucines at positions a and d in the coiled-coil heptad repeats were mutated to glycines. These coiled-coil mutants were still capable of autophosphorylation and transphosphorylation of peptides, but the rates of their kinase activities were significantly lowered. Moreover, phosphorylation of the natural myotonic dystrophy protein kinase substrate, myosin phosphatase targeting subunit, was preserved, even though binding of the myotonic dystrophy protein kinase to the myosin phosphatase targeting subunit was strongly reduced. Furthermore, the association of myotonic dystrophy protein kinase isoform C to the mitochondrial outer membrane was weakened when the coiled-coil interaction was perturbed. Our findings indicate that the coiled-coil domain modulates myotonic dystrophy protein kinase multimerization, substrate binding, kinase activity and subcellular localization characteristics.
authors.affiliation: Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, the Netherlands.
authors.forename: René E M A
authors.initials: RE
authors.lastname: van Herpen
authors.forename: Jorrit V
authors.initials: JV
authors.lastname: Tjeertes
authors.forename: Susan A M
authors.initials: SA
authors.lastname: Mulders
authors.forename: Ralph J A
authors.initials: RJ
authors.lastname: Oude Ophuis
authors.forename: Bé
authors.initials: B
authors.lastname: Wieringa
authors.forename: Derick G
authors.initials: DG
authors.lastname: Wansink
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism*; D065636:Myotonin-Protein Kinase; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014162:Transfection
chemical_list: C585517:DMPK protein, human; C585516:DMPK protein, mouse; D020033:Protein Isoforms; D011494:Protein Kinases; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases; D043263:Myosin-Light-Chain Phosphatase; C490372:PPP1R12A protein, human