title: Divergent mitochondrial and endoplasmic reticulum association of DMPK splice isoforms depends on unique sequence arrangements in tail anchors.
abstract: Myotonic dystrophy protein kinase (DMPK) is a Ser/Thr-type protein kinase with unknown function, originally identified as the product of the gene that is mutated by triplet repeat expansion in patients with myotonic dystrophy type 1 (DM1). Alternative splicing of DMPK transcripts results in multiple protein isoforms carrying distinct C termini. Here, we demonstrate by expressing individual DMPKs in various cell types, including C(2)C(12) and DMPK(-/-) myoblast cells, that unique sequence arrangements in these tails control the specificity of anchoring into intracellular membranes. Mouse DMPK A and C were found to associate specifically with either the endoplasmic reticulum (ER) or the mitochondrial outer membrane, whereas the corresponding human DMPK A and C proteins both localized to mitochondria. Expression of mouse and human DMPK A-but not C-isoforms in mammalian cells caused clustering of ER or mitochondria. Membrane association of DMPK isoforms was resistant to alkaline conditions, and mutagenesis analysis showed that proper anchoring was differentially dependent on basic residues flanking putative transmembrane domains, demonstrating that DMPK tails form unique tail anchors. This work identifies DMPK as the first kinase in the class of tail-anchored proteins, with a possible role in organelle distribution and dynamics.
authors.affiliation: Department of Cell Biology, NCMLS, Geert Grooteplein 28, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: René E M A
authors.initials: RE
authors.lastname: van Herpen
authors.forename: Ralph J A
authors.initials: RJ
authors.lastname: Oude Ophuis
authors.forename: Mietske
authors.initials: M
authors.lastname: Wijers
authors.forename: Miranda B
authors.initials: MB
authors.lastname: Bennink
authors.forename: Fons A J
authors.initials: FA
authors.lastname: van de Loo
authors.forename: Jack
authors.initials: J
authors.lastname: Fransen
authors.forename: Bé
authors.initials: B
authors.lastname: Wieringa
authors.forename: Derick G
authors.initials: DG
authors.lastname: Wansink
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology / Q000648:ultrastructure; D051379:Mice; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D032446:Myoblasts / Q000201:enzymology* / Q000648:ultrastructure; D009223:Myotonic Dystrophy / Q000378:metabolism; D065636:Myotonin-Protein Kinase; D041681:NIH 3T3 Cells; D020033:Protein Isoforms / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D019680:Trinucleotide Repeat Expansion / Q000502:physiology
chemical_list: C585517:DMPK protein, human; C585516:DMPK protein, mouse; D020033:Protein Isoforms; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases