Comparison of the subcellular localization of phosphodiesterase (PDE4) of normal and dystrophic mouse skeletal muscle

Abstract

There are four genes that encode members of the cyclic nucleotide phosphodiesterase 4 (PDE4) family. Earlier work in the lab has shown that there is a decrease in particulate PDE4 activity between 5 and 15 weeks of age in skeletal muscle from the muscular dystrophy model mdx. Western blot bands in particulate fractions from mdx muscle show an age‐related decrease in PDE4 protein. In this study, PDE4 was examined immunohistochemically to determine whether the expression changes correspond to an alteration in subcellular localization. Skeletal muscle from hind legs was harvested and frozen in Neg‐50 tissue sectioning media, and sectioned in 10 µm thick longitudinal and cross‐sections. Sections were probed with an antiserum specific for PDE4A or an antiserum that recognizes multiple PDE4 families. Bound antibodies were visualized by confocal microscopy using a fluorescently‐tagged secondary antibody. The anti‐PDE4A antibody showed staining at the sarcolemma of 5 week‐old normal and mdx muscle. This staining was retained through 15 weeks. Imaging with the non‐selective PDE4 antiserum showed a stronger signal for PDE4 localized along the sarcolemma in 5 week‐old normal muscle compared to mdx muscle. These observations suggest that a PDE4 other than PDE4A is responsible for the observed age‐related differences in PDE4 expression seen in mdx muscle. This project was supported by NIH Grant 1R15AR050408‐01A2 from NIAMS.