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Expression of a dystrophin-related protein associated with the skeletal muscle cell membrane
H Tanaka1, T Ishiguro, C Eguchi
1National Institute of Neuroscience NCNP, Tokyo, Japan.
Abstract:
We previously reported that a protein which has immunological cross-reactivity with and a molecular weight similar to dystrophin, the Duchenne muscular dystrophy (DMD) gene product, is expressed on the muscle cell membrane (Tanaka et al. 1989b). To examine if this is the translation product of the autosomal transcript with homology to dystrophin mRNA identified by Love et al. (1989), we raised an antibody (PDRP) against a synthetic peptide corresponding to the putative protein (DRP) and examined its expression and cellular localization in human and murine skeletal muscle samples. In immunoblotting, PDRP stained a band with a similar molecular weight to dystrophin in samples from DMD and Becker muscular dystrophy (BMD) patients and control (non-DMD/BMD) human. PDRP was expected not to cross-react with dystrophin because the antigenic peptide was not homologous to dystrophin. In fact, PDRP did not cross-react with dystrophin present in a BMD patient. Immunohistochemically, PDRP stained the muscle cell membrane in samples from DMB and BMD patients and from mdx mice. Only a slight staining was observed in muscles from control human and wild type mice. Our results confirm the presence of DRP in human and murine skeletal muscles, and further demonstrate that it is localized on the cell membrane. The abundance of DRP in dystrophin deficient muscles might be related to some compensatory mechanisms.
Insights
Researchers identified a novel protein, DRP, in muscle cell membranes, distinct from dystrophin. Its presence in dystrophin-deficient muscles suggests a compensatory role in muscular dystrophy.
Area of Science:
- Molecular Biology
- Cell Biology
- Neuromuscular Disorders
Background:
- A protein immunologically similar to dystrophin is found on muscle cell membranes.
- Dystrophin is the gene product associated with Duchenne muscular dystrophy (DMD).
- An autosomal transcript homologous to dystrophin mRNA has been identified.
Purpose of the Study:
- To determine if the identified protein (DRP) is the translation product of the autosomal transcript.
- To examine the expression and cellular localization of DRP in human and murine skeletal muscle.
Main Methods:
- Raised an antibody (PDRP) against a synthetic peptide of the putative protein (DRP).
- Performed immunoblotting and immunohistochemistry on human and murine skeletal muscle samples.
- Analyzed samples from Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and control individuals, as well as mdx mice.
Main Results:
- PDRP detected a dystrophin-like band in immunoblotting of DMD, BMD, and control human samples.
- PDRP did not cross-react with dystrophin in Becker muscular dystrophy patients.
- Immunohistochemistry showed PDRP localized to the muscle cell membrane in DMD, BMD patients, and mdx mice, with minimal staining in controls.
Conclusions:
- Confirmed the presence and muscle cell membrane localization of DRP in humans and mice.
- DRP is distinct from dystrophin, as indicated by the lack of cross-reactivity.
- Increased DRP abundance in dystrophin-deficient muscles may indicate a compensatory mechanism.