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This Article Full Text Full Text (PDF) All Versions of this Article: 586/6/1699    most recent jphysiol.2007.149500v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Wu, X. Articles by Davis, M. J. Search for Related Content PubMed PubMed Citation Articles by Wu, X. Articles by Davis, M. J. Related Collections Cardiovascular

¹ Department of Medical Pharmacology & Physiology and Dalton Cardiovascular Research Center, University of Missouri School of Medicine, Columbia, MO 65212, USA
² Department of Systems Biology & Translational Medicine, Texas A&M Health Science Center, College Station, TX 77843, USA
³ Department of Physiology, Osaka Medical College, Takatsuki, Osaka 569–8686, Japan
⁴ Smooth Muscle Research Group, University of Calgary School of Medicine, Calgary, Alberta, Canada T2N 4 N1

Injury/degradation of the extracellular matrix (ECM) is associated with vascular wall remodelling and impaired reactivity, a process in which altered ECM–integrin interactions play key roles. Previously, we found that peptides containing the RGD integrin-binding sequence produce sustained vasodilatation of rat skeletal muscle arterioles. Here, we tested the hypothesis that RGD ligands work through 5β1 integrin to modulate the activity of large conductance, Ca²⁺-activated K⁺ (BK) channels in arteriolar smooth muscle. K⁺ currents were recorded in single arteriolar myocytes using whole-cell and single-channel patch clamp methods. Activation of 5β1 integrin by an appropriate, insoluble 5β1 antibody resulted in a 30–50% increase in the amplitude of iberiotoxin (IBTX)-sensitive, whole-cell K⁺ current. Current potentiation occurred 1–8 min after bead–antibody application to the cell surface. Similarly, the endogenous 5β1 integrin ligand fibronectin (FN) potentiated IBTX-sensitive K⁺ current by 26%. Current potentiation was blocked by the c-Src inhibitor PP2 but not by PP3 (0.1–1 µM). In cell-attached patches, number of open channels x open probability (NP_o) of a 230–250 pS K⁺ channel was significantly increased after FN application locally to the external surface of cell-attached patches through the recording pipette. In excised, inside-out patches, the same method of FN application led to large, significant increases in NP_o and caused a leftward shift in the NP_o–voltage relationship at constant [Ca²⁺]. PP2 (but not PP3) nearly abolished the effect of FN on channel activity, suggesting that signalling between the integrin and channel involved an increase in Ca²⁺sensitivity of the channel via a membrane-delimited pathway. The effects of 5β1 integrin activation on both whole-cell and single-channel BK currents could be reproduced in HEK 293 cells expressing the BK channel -subunit. This is the first demonstration at the single-channel level that integrin signalling can regulate an ion channel. Our results show that 5β1 integrin activation potentiates BK channel activity in vascular smooth muscle through both Ca²⁺- and c-Src-dependent mechanisms. This mechanism is likely to play a role in the arteriolar dilatation and impaired vascular reactivity associated with ECM degradation.

(Received 6 December 2007; accepted after revision 23 January 2008; first published online 24 January 2008)
Corresponding author M. J. Davis: Department of Medical Pharmacology & Physiology, University of Missouri School of Medicine, 1 Hospital Dr, Rm M451, Columbia, MO 65212, USA. Email: davismj{at}health.missouri.edu