title: MG53's new identity.
abstract: Mitsugumin 53 (MG53) is a relatively newly identified tripartite motif-containing (TRIM) family muscle-specific E3 ubiquitin ligase that is expressed in skeletal muscle and the heart. It has been postulated to facilitate repair by targeting the site of an injury, and acting as a scaffold for assembly of a repair complex made up of dysferlin, annexin V, caveolin-3, and polymerase I and transcript release factor (PTRF). A recent letter published in Nature by Song et al. proposes an alternate function for MG53: as an E3 ligase that targets the insulin receptor and insulin receptor substrate 1 (IRS1) for degradation, therefore regulating muscle insulin signaling. This work is exciting, as it not only presents a novel role for MG53, but also suggests that muscle insulin signaling has a systemic influence on insulin resistance and the metabolic syndrome.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Levy
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Campbell
authors.affiliation: Novartis Institutes for Biomedical Research, 100 Technology Square, Cambridge, MA 02139, USA. david.glass@novartis.com.
authors.forename: David J
authors.initials: DJ
authors.lastname: Glass