title: Diacylglycerol kinase-zeta localization in skeletal muscle is regulated by phosphorylation and interaction with syntrophins.
abstract: Syntrophins are scaffolding proteins that link signaling molecules to dystrophin and the cytoskeleton. We previously reported that syntrophins interact with diacylglycerol kinase-zeta (DGK-zeta), which phosphorylates diacylglycerol to yield phosphatidic acid. Here, we show syntrophins and DGK-zeta form a complex in skeletal muscle whose translocation from the cytosol to the plasma membrane is regulated by protein kinase C-dependent phosphorylation of the DGK-zeta MARCKS domain. DGK-zeta mutants that do not bind syntrophins were mislocalized, and an activated mutant of this sort induced atypical changes in the actin cytoskeleton, indicating syntrophins are important for localizing DGK-zeta and regulating its activity. Consistent with a role in actin organization, DGK-zeta and syntrophins were colocalized with filamentous (F)-actin and Rac in lamellipodia and ruffles. Moreover, extracellular signal-related kinase-dependent phosphorylation of DGK-zeta regulated its association with the cytoskeleton. In adult muscle, DGK-zeta was colocalized with syntrophins on the sarcolemma and was concentrated at neuromuscular junctions (NMJs), whereas in type IIB fibers it was found exclusively at NMJs. DGK-zeta was reduced at the sarcolemma of dystrophin-deficient mdx mouse myofibers but was specifically retained at NMJs, indicating that dystrophin is important for the sarcolemmal but not synaptic localization of DGK-zeta. Together, our findings suggest syntrophins localize DGK-zeta signaling complexes at specialized domains of muscle cells, which may be critical for the proper control of lipid-signaling pathways regulating actin organization. In dystrophic muscle, mislocalized DGK-zeta may cause abnormal cytoskeletal changes that contribute to disease pathogenesis.
authors.affiliation: Department of Cellular and Molecular Medicine, Center for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Hanan
authors.initials: H
authors.lastname: Abramovici
authors.forename: Angela B
authors.initials: AB
authors.lastname: Hogan
authors.forename: Christopher
authors.initials: C
authors.lastname: Obagi
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Topham
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Gee
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism; D016189:Dystrophin / Q000378:metabolism; D049029:Dystrophin-Associated Proteins; D006801:Humans; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011554:Pseudopodia / Q000378:metabolism; D012508:Sarcolemma / Q000378:metabolism*; D013347:Subcellular Fractions
chemical_list: D000199:Actins; D004075:Diglycerides; D016189:Dystrophin; D049029:Dystrophin-Associated Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C091824:syntrophin; D019852:Diacylglycerol Kinase; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C