Calpain cleavage within dysferlin exon 40a releases a synaptotagmin-like module for membrane repair.
Bottom Line: Here we show that injury-activated cleavage of dysferlin is mediated by the ubiquitous calpains via a cleavage motif encoded by alternately spliced exon 40a.Of importance, we reveal that myoferlin and otoferlin are also cleaved enzymatically to release similar C-terminal modules, bearing two C2 domains and a transmembrane domain.Evolutionary preservation of this feature highlights its functional importance and suggests that this highly conserved C-terminal region of ferlins represents a functionally specialized vesicle fusion module.
Affiliation: Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Sydney, NSW 2145, Australia Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, Australia.Show MeSH
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Mentions: We next investigated whether calpain cleavage was a unique property of dysferlin or whether other members of the ferlin family share this property. We derived expression constructs of myoferlin and otoferlin and immunopurified each ferlin paralogue from transfected HEK293 cells using a luminal FLAG tag conjugated to the C-terminus. In vitro calpain cleavage revealed that exon 40a–containing dysferlin, myoferlin, and otoferlin were rapidly cleaved at a single, dominant cleavage site, releasing C-terminal (Figure 7A, top) and N-terminal (Figure 7A, bottom) fragments. In each case, the predicted products bear two C2 domains anchored by their transmembrane domain, a structure similar to that of the synaptotagmin family of vesicle fusion proteins (Figure 7C).
Affiliation: Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Sydney, NSW 2145, Australia Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, Australia.