Cadherins Mediate Intercellular Mechanical Signaling in Fibroblasts by Activation of Stretch-sensitive Calcium-permeable Channels

Abstract

Cells in mechanically active environments form extensive, cadherin-mediated intercellular junctions that are important in tissue remodeling and differentiation. Currently, it is unknown whether adherens junctions in connective tissue fibroblasts transmit mechanical signals and coordinate multicellular adaptations to physical forces. We hypothesized that cadherins mediate intercellular mechanotransduction by activating calciumpermeable, stretch-sensitive channels. Human gingival fibroblasts in suspension were plated on established homotypic monolayer cultures. The cells formed intercellular adherens junctions. Controlled mechanical forces were applied to intercellular junctions by electromagnets acting on cells containing internalized magnetite beads. At early but not later stages of intercellular attachment, force application visibly displaced magnetite bead-loaded cells and induced robust Ca 2؉ transients (65 ؎ 9.4 nM above base line). Similar Ca 2؉ transients were induced by force application to anti-N-cadherin antibody-coated magnetite beads. Ca 2؉ responses depended on influx of extracellular Ca 2؉ through mechanosensitive channels because both Ca 2؉ chelation and gadolinium chloride abolished the response and MnCl 2 quenched fura-2 fluorescence after force application. Force application induced accumulation of microinjected rhodamine-actin at intercellular contacts; actin assembly was inhibited by buffering intracellular calcium fluxes. Our results indicate that mechanical forces applied to adherens junctions activate stretch-sensitive calcium-permeable channels and increase actin polymerization. We suggest that N-cadherins in fibroblasts are intercellular mechanotransducers.

Regulation of Intercellular Adhesion Strength in Fibroblasts

“…Our results demonstrated an influx of calcium ions through the plasma mem- brane that was localized to sites of N-cadherin ligation and that appears to be important for activating cadherin-associated gelsolin severing activity. Previous reports have shown that in fibroblasts undergoing cadherin ligation, calcium influx occurs through plasma membrane channels located at nascent but not mature N-cadherin-mediated intercellular junctions (45). We found that blockade of this calcium entry resulted in marked reductions of nascent adhesion strength in gelsolin wild-type cells but had no effect on gelsolin-null cells.…”

“…Indeed, the gelsolin-null cells exhibited measurable severing activity and actin assembly when plated on N-cadherin substrates, albeit at greatly reduced rates when compared with wild-type cells. We suggest that the intracellular calcium transients following N-cadherin ligation (45) are important in intercellular adhesion because of their role in locally activating gelsolin severing activity.…”

Mutations in the desmosomal protein plakophilin-2 are common in arrhythmogenic right ventricular cardiomyopathy

“…Desmosomal proteins also have a role in cell signaling 5,6 . At least three groups of molecules contribute to the formation of desmosomes: desmosomal cadherins, armadillo-repeat proteins and plakins 7 .…”

Signal transduction of erbB receptors in trastuzumab (Herceptin) sensitive and resistant cell lines: Local stimulation using magnetic microspheres as assessed by quantitative digital microscopy

“…Immunomagnetic microsphere separation and microparticle based flow cytometry play an important role in experimental protocols and analytical procedures (19,20). Recently, microspheres have also served as powerful tools for studying complex cell biological phenomena such as collagen phagocytosis in fibroblasts (21,22), viscoelastic responses of endothelial cells upon thrombin stimulation measured by magnetic microsphere-based microrheology (23), and re-organization of lipid rafts and signalling complexes upon various stimuli (24)(25)(26)(27)(28)(29)(30).…”