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First published online 31 May 2005
doi: 10.1242/jcs.02395

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Laminin-6 assembles into multimolecular fibrillar complexes with perlecan and participates in mechanical-signal transduction via a dystroglycan-dependent, integrin-independent mechanism

¹ Division of Pulmonary Medicine, Feinberg School of Medicine, Northwestern University, Morton 4-616, 303 East Chicago Avenue, Chicago, IL 60611, USA
² Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Morton 4-616, 303 East Chicago Avenue, Chicago, IL 60611, USA
³ Howard Hughes Medical Institute, Roy J. and Lucille A. Carver College of Medicine, Department of Physiology and Biophysics, University of Iowa, 400 Eckstein Medical Research Building, Iowa City, IA 52242, USA

^* Author for correspondence (e-mail: j-jones3{at}northwestern.edu)

Accepted 22 March 2005

Mechanical ventilation is a valuable treatment regimen for respiratory failure. However, mechanical ventilation (especially with high tidal volumes) is implicated in the initiation and/or exacerbation of lung injury. Hence, it is important to understand how the cells that line the inner surface of the lung [alveolar epithelial cells (AECs)] sense cyclic stretching. Here, we tested the hypothesis that matrix molecules, via their interaction with surface receptors, transduce mechanical signals in AECs. We first determined that rat AECs secrete an extracellular matrix (ECM) rich in anastamosing fibers composed of the 3 laminin subunit, complexed with ß1 and 1 laminin subunits (i.e. laminin-6), and perlecan by a combination of immunofluorescence microscopy and immunoblotting analyses. The fibrous network exhibits isotropic expansion when exposed to cyclic stretching (30 cycles per minute, 10% strain). Moreover, this same stretching regimen activates mitogen-activated-protein kinase (MAPK) in AECs. Stretch-induced MAPK activation is not inhibited in AECs treated with antagonists to 3 or ß1 integrin. However, MAPK activation is significantly reduced in cells treated with function-inhibiting antibodies against the 3 laminin subunit and dystroglycan, and when dystroglycan is knocked down in AECs using short hairpin RNA. In summary, our results support a novel mechanism by which laminin-6, via interaction with dystroglycan, transduces a mechanical signal initiated by stretching that subsequently activates the MAPK pathway in rat AECs. These results are the first to indicate a function for laminin-6. They also provide novel insight into the role of the pericellular environment in dictating the response of epithelial cells to mechanical stimulation and have broad implications for the pathophysiology of lung injury.

Key words: Matrix adhesion, Matrix receptors, Stretching

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