Submitted on September 12, 2007
Accepted on November 3, 2007
Expression of the dystrophin glycoprotein complex is a marker for human airway smooth muscle phenotype maturation
Pawan Sharma1, Thai Tran2, Gerald L Stelmack3, Karol D. McNeill3, Reinoud Gosens4, Mark M Mutawe3, Helmut Unruh5, William T. Gerthoffer6, and Andrew John Halayko7*
1 Physiology, University of Manitoba, Respiratory Research Group, winnipeg, R3E3P4, Canada; CIHR National Training Program in Allergy and Asthma, University of Manitoba, Winnipeg, Canada; Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada
2 Physiology, University of Manitoba, Winnipeg, Canada; CIHR National Training Program in Allergy and Asthma, University of Manitoba, Winnipeg, Canada; Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada
3 Physiology, University of Manitoba, Winnipeg, Canada; Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada
4 Molecular Pharmacology, University of Groningen, Groningen, Netherlands; Physiology, University of Manitoba, Winnipeg, Canada; Section of Respiratory Diseases, University of Manitoba, Winnipeg, Canada; CIHR National Training Program in Allergy and Asthma, University of Manitoba, Winnipeg, Canada; Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada
5 Section of Thoracic Surgery, University of Manitoba, Winnipeg, Canada; Internal Medicine, University of Manitoba, Winnipeg, Canada
6 Department of Biochemistry & Molecular Biology, University of South Alabama, College of Medicine, Mobile, Alabama, United States
7 Physiology, University of Manitoba, Winnipeg, Canada; Internal Medicine, University of Manitoba, Winnipeg, Canada; Pediatrics and Child Health, University of Manitoba, Winnipeg, Canada; Section of Respiratory Diseases, University of Manitoba, Winnipeg, Canada; CIHR National Training Program in Allergy and Asthma, University of Manitoba, Winnipeg, Canada; Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada
* To whom correspondence should be addressed. E-mail: ahalayk{at}cc.umanitoba.ca.
Airway smooth muscle (ASM) cells may contribute to asthma pathogenesis through their capacity to switch between a synthetic/proliferative and contractile phenotype. The multimeric dystrophin glycoprotein complex (DGC) spans the sarcolemma, linking the actin cytoskeleton and extracellular matrix. The DGC is expressed in smooth muscle tissue, but its functional role is not fully established. We tested whether contractile phenotype maturation of human ASM is associated with accumulation of DGC proteins. We compared subconfluent, serum-fed cultures and confluent cultures subjected to serum deprivation, which express a contractile phenotype. Western blotting confirmed that 
-dystroglycan, -, 
- and 
- sarcoglycan, and dystrophin abundance increased 6-8 fold in association with smooth muscle myosin (smMHC) and calponin accumulation during 4-days serum deprivation. Immunocytochemistry showed that the accumulation of DGC subunits was specifically localized to a subset of cells that exhibit robust staining for smMHC. Laminin competing peptide (YIGSR, 1µM) and phosphatidylinositide-3-kinase (PI3K) inhibitors (20µM LY294002 or 100nM wortmannin) abrogated the accumulation of smMHC, calponin and DGC proteins. These studies demonstrate that the accumulation of DGC is an integral feature for phenotype maturation of human ASM cells. This provides strong rationale for future studies investigating the role of the DGC in ASM smooth muscle physiology in health and disease.
