MURF-1 and MURF-2 target a specific subset of myofibrillar proteins redundantly: Towards understanding MURF-dependent muscle ubiquitination

Stephanie H. Witt, Henk Granzier, Christian C. Witt, Siegfried Labeit

Research output: Contribution to journalArticle

208 Scopus citations

Abstract

MURF-1, MURF-2 and MURF-3 are a specific class of RING finger proteins that are expressed in striated muscle tissues. MURF-1 has been suggested to act as an ubiquitin ligase, thereby controlling proteasome-dependent degradation of muscle proteins. Here, we performed yeast two-hybrid (YTH) screens of skeletal muscle cDNA libraries with MURF-1 baits to identify potential myocellular targets of MURF-1-dependent ubiquitination. This identified eight myofibrillar proteins as binding partners of MURF-1: titin, nebulin, the nebulin-related protein NRAP, troponin-I (TnI), troponin-T (TnT), myosin light chain 2 (MLC-2), myotilin and T-cap. YTH mating studies with MURF-1,2,3 baits indicated that these eight myofibrillar proteins are all targeted redundantly by both MURF-1 and MURF-2. Western blot studies on cardiac tissues from wild-type and MURF-1-deficient mice suggested that titin and nebulin were ubiquitinated at similar levels, and MLC-2 and TnI at reduced levels in MURF-1 KO mice. Mapping of the TnI and titin binding sites on MURF-1 peptide scans demonstrated their binding to motifs highly conserved between MURF-1 and MURF-2. Our data are consistent with a model in which MURF-1 and MURF-2 together target a specific set of myofibrillar proteins redundantly, most likely to control their ubiquitination-dependent degradation. Finally, our YTH screens identified the interaction of MURF-1 with 11 enzymes required for ATP/energy production in muscle including the mitochondrial ATP synthase and cytoplasmic creatine kinase. These data raise the possibility that MURF-1 may coordinately regulate the energy metabolism of mitochondrial and cytoplasmic compartments.

Original languageEnglish (US)
Pages (from-to)713-722
Number of pages10
JournalJournal of Molecular Biology
Volume350
Issue number4
DOIs
StatePublished - Jul 22 2005
Externally publishedYes

Keywords

  • Energy metabolism
  • Muscle RING finger proteins MURFs
  • Proteolysis
  • Titin
  • Ubiquitin

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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