TY  - JOUR
A1  - Kirschmer, Nadine
A1  - Bandleon, Sandra
A1  - von Ehrlich-Treuenstätt, Viktor
A1  - Hartmann, Sonja
A1  - Schaaf, Alice
A1  - Lamprecht, Anna-Karina
A1  - Miranda-Laferte, Erick
A1  - Langsenlehner, Tanja
A1  - Ritter, Oliver
A1  - Eder, Petra
T1  - TRPC4α and TRPC4β Similarly Affect Neonatal Cardiomyocyte Survival during Chronic GPCR Stimulation
JF  - PLoS ONE
N2  - The Transient Receptor Potential Channel Subunit 4 (TRPC4) has been considered as a crucial Ca\(^{2+}\) component in cardiomyocytes promoting structural and functional remodeling in the course of pathological cardiac hypertrophy. TRPC4 assembles as homo or hetero-tetramer in the plasma membrane, allowing a non-selective Na\(^{+}\) and Ca\(^{2+}\) influx. Gαq protein-coupled receptor (GPCR) stimulation is known to increase TRPC4 channel activity and a TRPC4-mediated Ca\(^{2+}\) influx which has been regarded as ideal Ca\(^{2+}\) source for calcineurin and subsequent nuclear factor of activated T-cells (NFAT) activation. Functional properties of TRPC4 are also based on the expression of the TRPC4 splice variants TRPC4α and TRPC4β. Aim of the present study was to analyze cytosolic Ca\(^{2+}\) signals, signaling, hypertrophy and vitality of cardiomyocytes in dependence on the expression level of either TRPC4α or TRPC4β. The analysis of Ca\(^{2+}\) transients in neonatal rat cardiomyocytes (NRCs) showed that TRPC4α and TRPC4β affected Ca\(^{2+}\) cycling in beating cardiomyocytes with both splice variants inducing an elevation of the Ca\(^{2+}\) transient amplitude at baseline and TRPC4β increasing the Ca\(^{2+}\) peak during angiotensin II (Ang II) stimulation. NRCs infected with TRPC4β (Ad-C4β) also responded with a sustained Ca\(^{2+}\) influx when treated with Ang II under non-pacing conditions. Consistent with the Ca\(^{2+}\) data, NRCs infected with TRPC4α (Ad-C4α) showed an elevated calcineurin/NFAT activity and a baseline hypertrophic phenotype but did not further develop hypertrophy during chronic Ang II/phenylephrine stimulation. Down-regulation of endogenous TRPC4α reversed these effects, resulting in less hypertrophy of NRCs at baseline but a markedly increased hypertrophic enlargement after chronic agonist stimulation. Ad-C4β NRCs did not exhibit baseline calcineurin/NFAT activity or hypertrophy but responded with an increased calcineurin/NFAT activity after GPCR stimulation. However, this effect was not translated into an increased propensity towards hypertrophy but rather less hypertrophy during GPCR stimulation. Further analyses revealed that, although hypertrophy was preserved in Ad-C4α NRCs and even attenuated in Ad-C4β NRCs, cardiomyocytes had an increased apoptosis rate and thus were less viable after chronic GPCR stimulation. These findings suggest that TRPC4α and TRPC4β differentially affect Ca\(^{2+}\) signals, calcineurin/NFAT signaling and hypertrophy but similarly impair cardiomyocyte viability during GPCR stimulation.
KW  - Apoptosis
KW  - calcineurin signaling cascade
KW  - small interfering RNAs
KW  - G protein coupled receptors
KW  - hyperexpression techniques
KW  - heart
KW  - adenoviruses
KW  - cardiac pacing
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178539
VL  - 11
IS  - 12
ER  - 
TY  - JOUR
A1  - Korb, Doreen
A1  - Tng, Priscilla Y.
A1  - Milenkovic, Vladimir M.
A1  - Reichhart, Nadine
A1  - Strauss, Olaf
A1  - Ritter, Oliver
A1  - Fischer, Tobias
A1  - Benz, Peter M.
A1  - Schuh, Kai
T1  - Identification of PDZ domain containing proteins interacting with \(Ca_v1.2\) and PMCA4b
JF  - ISRN Cell Biology
N2  - PDZ (PSD-95/Disc large/Zonula occludens-1) protein interaction domains bind to cytoplasmic protein C-termini of transmembrane proteins. In order to identify new interaction partners of the voltage-gated L-type \(Ca^{2+}\) channel Cav1.2 and the plasma membrane \(Ca^{2+}\) ATPase 4b (PMCA4b), we used PDZ domain arrays probing for 124 PDZ domains. We confirmed this byGST pulldowns and immunoprecipitations. In PDZ arrays, strongest interactionswith \(Ca_v1.2\) and PMCA4b were found for the PDZ domains of SAP-102, MAST-205, MAGI-1, MAGI-2, MAGI-3, and ZO-1. We observed binding of the \(Ca_v1.2\) C-terminus to PDZ domains of NHERF1/2, Mint-2, and CASK. PMCA4b was observed to interact with Mint-2 and its known interactions with Chapsyn-110 and CASK were confirmed. Furthermore, we validated interaction of \(Ca_v1.2\) and PMCA4b with NHERF1/2, CASK,MAST-205 and MAGI-3 viaimmunoprecipitation. We also verified the interaction of \(Ca_v1.2\) and nNOS and hypothesized that nNOS overexpression might reduce \(Ca^{2+}\) influx through \(Ca_v1.2\). To address this, we measured \(Ca^{2+}\) currents in HEK 293 cells co-expressing \(Ca_v1.2\) and nNOS and observed reduced voltage-dependent \(Ca_v1.2\) activation. Taken together, we conclude that \(Ca_v1.2\) and PMCA4b bind promiscuously to various PDZ domains, and that our data provides the basis for further investigation of the physiological consequences of these interactions.
KW  - Cell
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130585
IS  - Article ID 265182
ER  -