Enterovirus infection can cause severe
cardiomyopathy in humans. The virus-encoded 2A
protease is known to cleave the cytoskeletal
protein dystrophin. It is unclear, however, whether
cardiomyopathy results from the loss of
dystrophin or is due to the emergence of a dominant-negative
dystrophin cleavage product. We show for the first time that the 2A
protease-mediated carboxyl-terminal
dystrophin cleavage fragment (CtermDys) is sufficient to cause marked dystrophic
cardiomyopathy. The sarcolemma-localized CtermDys fragment caused myocardial
fibrosis, heightened susceptibility to myocardial ischemic injury, and increased mortality during cardiac stress testing in vivo. CtermDys
cardiomyopathy was more severe than in hearts completely lacking
dystrophin. In vivo titration of CtermDys
peptide content revealed an inverse relationship between the decay of membrane-bound CtermDys and the restoration of full-length
dystrophin at the sarcolemma, in support of a physiologically relevant loss of
dystrophin function in this model. CtermDys gene titration and
dystrophin replacement studies further established a target threshold of 50% membrane-bound intact
dystrophin necessary to prevent mice from CtermDys
cardiomyopathy. Conversely, the NtermDys fragment did not compete with
dystrophin and had no pathological effect. Thus, CtermDys must be localized to the sarcolemma, with intact
dystrophin <50% of normal levels, to exert dominant-negative
peptide-dependent
cardiomyopathy. These data support a two-hit dominant-negative disease mechanism where membrane-associated CtermDys severs the link to cortical actin and inhibits both full-length
dystrophin and compensatory
utrophin from binding at the membrane. Therefore, membrane-bound CtermDys is a new potential translational target for virus-mediated
cardiomyopathy.