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This Article Full Text Full Text (PDF) All Versions of this Article: 289/6/H2526    most recent 00658.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Sun, Z. Articles by Meininger, G. A. Search for Related Content PubMed PubMed Citation Articles by Sun, Z. Articles by Meininger, G. A.

Mechanical properties of the interaction between fibronectin and ₅₁-integrin on vascular smooth muscle cells studied using atomic force microscopy

¹Department of Medical Physiology, ²Department of Pharmacology and Toxicology, and ³Department of Pathology and Laboratory Medicine, Cardiovascular Research Institute-Division of Vascular Biology, Texas A&M University System Health Science Center, College Station, Texas; and ⁴Institute of Physiology, Ludwig Maximilians University, Munich, Germany

Submitted 2 July 2004 ; accepted in final form 4 August 2005

The mechanical properties of integrin-extracellular matrix (ECM) interactions are important for the mechanotransduction of vascular smooth muscle cells (VSMC), a process that is associated with focal adhesions, and can be of particular significance in cardiovascular disease. In this study, we characterized the unbinding force and binding activity of the initial fibronectin (FN)-₅₁ interaction on the surface of VSMC using atomic force microscopy (AFM). It is postulated that these initial binding events are important to the subsequent focal adhesion assembly. FN-VSMC adhesions were selectively blocked by antibodies against ₅- and ₁-integrins as well as RGD-containing peptides but not by antibodies against ₄- and ₃-integrins, indicating that FN primarily bound to ₅₁. A characteristic unbinding force of 39 ± 8 pN was observed and interpreted to represent the FN-₅₁ single-bond strength. The ability of FN to adhere to VSMC (binding probability) was significantly reduced by integrin antagonists, serum starvation, and platelet-derived growth factor (PDGF)-BB, whereas lysophosphatidic acid (LPA) increased FN binding. However, no significant change in the resolved unbinding force was observed. After engagement, the force required to dislodge the FN-coated bead from VSMC increased with increasing of contact time, suggesting a time-dependent increase in number of adhesions and/or altered binding affinity. LPA enhanced this process, whereas PDGF reduced it, suggesting that these factors also affect the multimolecular process of focal contact assembly. Thus AFM is a powerful tool for the characterization of the mechanical properties of integrin-ECM interactions and their regulation. Our results indicate that the functional activity of ₅₁ and focal contact assembly can be rapidly regulated.

bond strength; lysophosphatidic acid; platelet-derived growth factor; mechanical forces; mechanobiology; focal adhesions; focal contacts

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