title: The E3 ubiquitin ligase TRIM32 regulates myoblast proliferation by controlling turnover of NDRG2.
abstract: Limb girdle muscular dystrophy 2H is caused by mutations in the gene encoding the E3 ubiquitin ligase, TRIM32. Previously, we generated and characterized a Trim32 knockout mouse (T32KO) that displays both neurogenic and myopathic features. The myopathy in these mice is attributable to impaired muscle growth, associated with satellite cell senescence and premature sarcopenia. This satellite cell senescence is due to accumulation of the SUMO ligase PIASy, a substrate of TRIM32. The goal of this investigation was to identify additional substrates of TRIM32 using 2D fluorescence difference gel electrophoresis (2D-DIGE) in order to further explore its role in skeletal muscle. Because TRIM32 is an E3 ubiquitin ligase, we reasoned that TRIM32's substrates would accumulate in its absence. 2D-DIGE identified 19 proteins that accumulate in muscles from the T32KO mouse. We focused on two of these proteins, NDRG2 and TRIM72, due to their putative roles in myoblast proliferation and myogenesis. Follow-up analysis confirmed that both proteins were ubiquitinated by TRIM32 in vitro; however, only NDRG2 accumulated in skeletal muscle and myoblasts in the absence of TRIM32. NDRG2 overexpression in myoblasts led to reduced cell proliferation and delayed cell cycle withdrawal during differentiation. Thus, we identified NDRG2 as a novel target for TRIM32; these findings further corroborate the hypothesis that TRIM32 is involved in control of myogenic cells proliferation and differentiation.
authors.affiliation: Department of Neurology and.
authors.forename: Ekaterina I
authors.initials: EI
authors.lastname: Mokhonova
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
authors.forename: Nuraly K
authors.initials: NK
authors.lastname: Avliyakulov
authors.affiliation: Department of Neurology and.
authors.forename: Irina
authors.initials: I
authors.lastname: Kramerova
authors.affiliation: Department of Neurology and.
authors.forename: Elena
authors.initials: E
authors.lastname: Kudryashova
authors.affiliation: Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Haykinson
authors.affiliation: Department of Neurology and Center for Duchenne Muscular Dystrophy at UCLA, Los Angeles, CA, USA and Molecular Biology Institute, UCLA, Los Angeles, CA, USA m.spencer@ucla.edu.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Spencer
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation; D004195:Disease Models, Animal; D055786:Gene Knockout Techniques; D051379:Mice; D018345:Mice, Knockout; D049288:Muscular Dystrophies, Limb-Girdle / Q000201:enzymology / Q000235:genetics*; D032446:Myoblasts / Q000201:enzymology* / Q000502:physiology; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D057825:Two-Dimensional Difference Gel Electrophoresis; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C485172:Ndr2 protein, mouse; D011506:Proteins; C514011:TRIM32 protein, mouse; D044767:Ubiquitin-Protein Ligases