Dataset Information

?-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

ABSTRACT: The N-cadherin (N-cad) complex plays a crucial role in cardiac cell structure and function. Cadherins are adhesion proteins linking adjacent cardiac cells and, like integrin adhesions, are sensitive to force transmission. Forces through these adhesions are capable of eliciting structural and functional changes in myocytes. Compared to integrins, the mechanisms of force transduction through cadherins are less explored. ?-catenin is a major component of the cadherin-catenin complex, thought to provide a link to the cell actin cytoskeleton. Using N-cad micropatterned substrates in an adhesion constrainment model, the results from this study show that ?-catenin localizes to regions of highest internal stress in myocytes. This localization suggests that ?-catenin acts as an adaptor protein associated with the cadherin mechanosensory apparatus, which is distinct from mechanosensing through integrins. Myosin inhibition in cells bound by integrins to fibronectin-coated patterns disrupts myofibiril organization, whereas on N-cad coated patterns, myosin inhibition leads to better organized myofibrils. This result indicates that the two adhesion systems provide independent mechanisms for regulating myocyte structural organization.

SUBMITTER: Chopra A

PROVIDER: S-EPMC3471892 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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α-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

Chopra Anant A Patel Akash A Shieh Adrian C AC Janmey Paul A PA Kresh J Yasha JY

PloS one 20121015 10

The N-cadherin (N-cad) complex plays a crucial role in cardiac cell structure and function. Cadherins are adhesion proteins linking adjacent cardiac cells and, like integrin adhesions, are sensitive to force transmission. Forces through these adhesions are capable of eliciting structural and functional changes in myocytes. Compared to integrins, the mechanisms of force transduction through cadherins are less explored. α-catenin is a major component of the cadherin-catenin complex, thought to pro ...[more]

PMID: 23077648

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Project description:Neuronal nicotinic acetylcholine receptors (nAChRs) are widely expressed throughout the central and peripheral nervous system and are localized at synaptic and extrasynaptic sites of the cell membrane. However, the mechanisms regulating the localization of nicotinic receptors in distinct domains of the cell membrane are not well understood. N-cadherin is a cell adhesion molecule that mediates homotypic binding between apposed cell membranes and regulates the actin cytoskeleton through protein interactions with the cytoplasmic domain. At synaptic contacts, N-cadherin is commonly localized adjacent to the active zone and the postsynaptic density, suggesting that N-cadherin contributes to the assembly of the synaptic complex. To examine whether N-cadherin homotypic binding regulates the cell surface localization of nicotinic receptors, this study used heterologous expression of N-cadherin and ?3?4 nAChR subunits C-terminally fused to a myc-tag epitope in Chinese hamster ovary cells. Expression levels of ?3?4 nAChRs at cell-cell contacts and at contact-free cell membrane were analyzed by confocal microscopy. ?3?4 nAChRs were found distributed over the entire surface of contacting cells lacking N-cadherin. In contrast, N-cadherin-mediated cell-cell contacts were devoid of ?3?4 nAChRs. Cell-cell contacts mediated by N-cadherin-deleted proteins lacking the ?-catenin binding region or the entire cytoplasmic domain showed control levels of ?3?4 nAChRs expression. Inhibition of actin polymerization with latrunculin A and cytochalasin D did not affect ?3?4 nAChRs localization within N-cadherin-mediated cell-cell contacts. However, treatment with the Rho associated kinase inhibitor Y27632 resulted in a significant increase in ?3?4 nAChR levels within N-cadherin-mediated cell-cell contacts. Analysis of ?3?4 nAChRs localization in polarized Caco-2 cells showed specific expression on the apical cell membrane and colocalization with apical F-actin and the actin nucleator Arp3. These results indicate that actomyosin contractility downstream of N-cadherin homotypic binding regulates the cell surface localization of ?3?4 nAChRs presumably through interactions with a particular pool of F-actin.

Project description:Wolframin (Wfs1) is a membrane protein of the sarco/endoplasmic reticulum. Wfs1 mutations are responsible for the Wolfram syndrome, characterized by diabetic and neurological symptoms. Although Wfs1 is expressed in cardiac muscle, its role in this tissue is not clear. We have characterized the effect of invalidation of Wfs1 on calcium signaling-related processes in isolated ventricular myocytes of exon5-Wfs1 deficient rats (Wfs1-e5/-e5) before the onset of overt disease. Calcium transients and contraction were measured in field-stimulated isolated myocytes using confocal microscopy with calcium indicator fluo-3 AM and sarcomere length detection. Calcium currents and their calcium release-dependent inactivation were characterized in whole-cell patch-clamp experiments. At 4 months, Wfs1-e5/-e5 animals were euglycemic, and echocardiographic examination revealed fully compensated cardiac function. In field-stimulated isolated ventricular myocytes, both the amplitude and the duration of contraction of Wfs1-e5/-e5 animals were elevated relative to control Wfs1+/+ littermates. Increased contractility of myocytes resulted largely from prolonged cytosolic calcium transients. Neither the amplitude of calcium currents nor their voltage dependence of activation differed between the two groups. Calcium currents in Wfs1-e5/-e5 myocytes showed a larger extent of inactivation by short voltage prepulses applied to selectively induce calcium release-dependent inactivation of calcium current. Neither the calcium content of the sarcoplasmic reticulum, measured by application of 20 mmol/l caffeine, nor the expression of SERCA2, determined from Western blots, differed significantly in myocytes of Wfs1-e5/-e5 animals compared to control ones. These experiments point to increased duration of calcium release in ventricular myocytes of Wfs1-e5/-e5 animals. We speculate that the lack of functional wolframin might cause changes leading to upregulation of RyR2 channels resulting in prolongation of channel openings and/or a delay in termination of calcium release.

Dataset Information

?-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

Publications

α-Catenin localization and sarcomere self-organization on N-cadherin adhesive patterns are myocyte contractility driven.

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