  In the peripheral nervous system, utrophin and the short dystrophin isoform
(Dp116) are co-localized at the outermost layer of the myelin sheath of nerve
fibers; together with the dystroglycan complex. In peripheral nerve, matrix
metalloproteinase (MMP) creates a 30 kDa fragment of beta-dystroglycan, leading
to a disruption of the link between the extracellular matrix and the cell
membrane. Here we asked if the processing of the beta-dystroglycan could
influence the anchorage of Dp116 or/and utrophin in normal and mdx Schwann cell
membrane. We showed that MMP-9 was more activated in mdx nerve than in
wild-type one. This activation leads to an accumulation of the 30 kDa
beta-dystroglycan isoform and have an impact on the anchorage of Dp116 and
utrophin isoforms in mdx Schwann cells membrane. Our results showed that Dp116
had greater affinity to the full length form of beta-dystroglycan than the 30
kDa form. Moreover, we showed for the first time that the short isoform of
utrophin (Up71) was over-expressed in mdx Schwann cells compared to wild-type.
In addition, this utrophin isoform (Up71) seems to have greater affinity to the
30 kDa beta-dystroglycan which could explain a more stabilization of this 30
kDa at the membrane compartment. Our results highlight the potential
participation of the short utrophin isoform and the cleaved form of
beta-dystroglycan in mdx Schwann cell membrane architecture.
