Function of TRIM32, the ubiquitin ligase mutated in Limb Girdle Muscular Dystrophy 2H

Germana Meroni

TRIM32 is the gene responsible for Limb Girdle Muscular Dystrophy type  2H and Sarcotubular Myopathy. The TRIM32 gene product is an E3 ubiquitin  ligase for which many substrates have been reported. To unravel its  function in muscular dystrophy, it is important to understand how TRIM32  pleiotropy is achieved. TRIM32 ability to homo-interact, thus offering  several RING moieties to E2 binding, and to interact with different E2  enzymes can underlie TRIM32 potential to form different complex  combinations. As E3-E2 pairs determine the type of ubiquitin  modification, this may result in the amplification of TRIM32 spectrum of  action in regulating the fate of several targets and implication in  diverse pathological conditions.

The objective of this project is to thoroughly define TRIM32 ubiquitin E3 ligase activity by assessing the  specific TRIM32-E2 complexes and the ubiquitin chains formed for the  control of specific muscular targets, combining biochemical, biophysical  and cell biology approaches.

ESR3 will investigate TRIM32 role and  biochemistry, self-interaction requirements, and potential to catalyse  different ubiquitin chain topologies, dissecting in vitro its E3  activity with different E2 enzyme combinations. These features will be  then validated on TRIM32 natural substrates in normal and pathological  cellular systems. C2C12 cells induced to differentiate into myofibers  and fibroblasts from LGMD2H patients differentiated towards a muscular  phenotype by MyoD transduction will be employed for these studies. The  accomplishment of the proposed experiments will elucidate the ability of  TRIM32 to use different partners within the ubiquitination machinery to  produce specific ubiquitin modifications of muscular substrates. These  data will be important for the design of muscular dystrophy therapies  without interfering with non-muscular pathways.

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