| Summary: | Members of the Kelch-like family display various functions at the cellular level, such as being involved in signalling pathways, as mediators of cytoskeletal changes and most prominently by targeting specific substrates for proteasomal degradation. Previous studies suggested a role for Kelch-like 31 (Klhl31) during myogenesis, as its expression is dependent on signals responsible for the induction of myogenesis in the somites and is slightly delayed compared to the expression of early myogenic regulatory factors. With this study we wanted to analyse the function of Klhl31 during myogenesis in more detail. Using C2C12 mouse myotubes as our model cell line to study myogenic differentiation and myofibrillogenesis, we found that Klhl31 is closely associated with Actin fibres in differentiated, multi-nucleated myotubes and that observed co-localisation can be linked to C2C12 differentiation. Furthermore, we used a Yeast-2-Hybrid screen approach and GST-pull downs to find interaction partners for Klhl31. Putative interacting proteins for Klhl31 were analysed and found to be structural components of the sarcomere with many of them also being involved in myofibrillogenesis, such as Nebulin, Actin, CapZ and tropomyosin. We also analysed a possible role of Klhl31 in proteasomal degradation, as Klhl31 was shown to negatively regulate canonical Wnt-signalling. We gathered evidence that Klhl31 might interact with components of E3-Ubiquitin ligase complexes and might target specific substrates including itself for degradation by the 26S proteasome. Furthermore, we analysed the expression of Klhl31 during heart development in chick embryos, where it was restricted to the myocardium. We concluded that Klhl31 might be important during myofibrillogenesis in striated muscles. A role for Klhl31 in mature muscle might involve providing structural stabilisation in sarcomeres and during muscle contraction.
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