Stretch of β1 Integrin Activates an Outwardly Rectifying Chloride Current via FAK and Src in Rabbit Ventricular Myocytes

Abstract

Osmotic swelling of cardiac myocytes and other types of cells activates an outwardly rectifying, tamoxifen-sensitive Cl− current, ICl,swell, but it is unclear whether Cl− currents also are activated by direct mechanical stretch. We tested whether specific stretch of β1-integrin activates a Cl− current in rabbit left ventricular myocytes. Paramagnetic beads (4.5-μm diameter) coated with mAb to β1-integrin were applied to the surface of myocytes and pulled upward with an electromagnet while recording whole-cell current. In solutions designed to isolate anion currents, β1-integrin stretch elicited an outwardly rectifying Cl− current with biophysical and pharmacological properties similar to those of ICl,swell. Stretch-activated Cl− current activated slowly (t1/2 = 3.5 ± 0.1 min), partially inactivated at positive voltages, reversed near ECl, and was blocked by 10 μM tamoxifen. When stretch was terminated, 64 ± 8% of the stretch-induced current reversed within 10 min. Mechanotransduction involved protein tyrosine kinase. Genistein (100 μM), a protein tyrosine kinase inhibitor previously shown to suppress ICl,swell in myocytes, inhibited stretch-activated Cl− current by 62 ± 6% during continued stretch. Because focal adhesion kinase and Src are known to be activated by cell swelling, mechanical stretch, and clustering of integrins, we tested whether these tyrosine kinases mediated the response to β1-integrin stretch. PP2 (10 μM), a selective blocker of focal adhesion kinase and Src, fully inhibited the stretch-activated Cl− current as well as part of the background Cl− current, whereas its inactive analogue PP3 (10 μM) had no significant effect. In addition to activating Cl− current, stretch of β1-integrin also appeared to activate a nonselective cation current and to suppress IK1. Integrins are the primary mechanical link between the extracellular matrix and cytoskeleton. The present results suggest that integrin stretch may contribute to mechano-electric feedback in heart, modulate electrical activity, and influence the propensity for arrhythmogenesis.

Big Signals from Small Particles: Regulation of Cell Signaling Pathways by Nanoparticles

“…5F). 96 Data suggest that integrin stretching may contribute to a mechano-electric feedback in the heart by modulating electrical activity. In a vascular endothelial cell model, integrin-linked magnetic beads were used to demonstrate that the transduction of local mechanical forces into biological signals is mediated through the activation of focal adhesion sites.…”

Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

“…Gramicidin was added as indicated by the arrow to ensure high cation permeability, i.e., to establish conditions where the rate of RVD is dictated by the Cl -permeability. cardiac ventricular myocytes is shown to regulate VRAC, 38 it is likely that inhibition of RVD by integrin b 1 knockdown in ELA cells involves inhibition of VRAC. VRAC current can in most cell types be activated under conditions with strongly buffered intracellular Ca 2C .…”

“…9D), (iv) sensitivity to membrane potential (VSOAC inhibited by depolarization / VRAC shows outward rectification and varying degree of inactivation at positive potentials 7 ), and (v) regulation via integrin b 1 , i.e., VSOAC is unaffected by integrin b 1 knockdown 37 whereas VRAC is activated by integrin b 1 stretch. 34,38,92 Variation in stoichiometry of LRRC8 components and their regulation / localization to subdomain in the plasma membrane could explain differences between VSOAC and VRAC activities (see below).…”

ICln, a Novel Integrin αIIbβ3-Associated Protein, Functionally Regulates Platelet Activation

“…A number of groups have demonstrated that integrins regulate potassium, calcium, or chloride fluxes either indirectly (17)(18)(19)(20)(21)(22) or directly (19, 21, 23, 26 -28). Vitronectin, but not fibrinonectin or laminin, selectively affects potassium currents in an Arg-Gly-Asp sequence-dependent manner in developing mouse hippocampal neurons (29).…”

“…It is found in the cytosol in cells-at-rest but is associated with the cell membrane following a hypotonic challenge. Thus, physiological cell swelling stimulates cytosol to membrane transposition of ICln (21). However, controversy arises over this hypothesis (38).…”