Dysferlin and Acute Membrane Resealing; Is This its Real Job?

Angela Lek 1,2, Frances J Evesson 1,2, Joanne Hawkes 1, Frances A Lemckert 1,2, Fabienne Brillot 1,2, Russell C Dale 1,2, North N Kathryn 1, Sandra T. Cooper 1,2

1 Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, Australia;  2 Discipline of Paediatrics and Child Health, University of Sydney, Australia

  We have studied the consequences of dysferlin deficiency and dysferlin overexpression upon acute membrane resealing in cultured skeletal myotubes.  Our studies employ mechanical (microparticle ballistics) and detergent-based (saponin) membrane damage. Our detergent-based damage assay demonstrates that dysferlin knock-down cells have a modest resealing defect, most profoundly observed at extremes of damage.  In contrast, dysferlin overexpression significantly impairs membrane resealing, as does expression of dysferlin mutants.  Using ballistics, we have studied the calcium- and dysferlin-dependent recruitment of dysferlin-interacting proteins MG53 and annexin A1 to sites of membrane injury.  We have no evidence that dysferlin is subject to regulated exocytosis in response to a membrane injury event.  Our data therefore suggests that it is dysferlin already localised within the plasma membrane that plays a key role in membrane resealing at the time of injury, and/or, that other functions of dysferlin secondarily impact membrane resealing.