TY  - JOUR
A1  - Seidlmayer, Lea K.
A1  - Mages, Christine
A1  - Berbner, Annette
A1  - Eder-Negrin, Petra
A1  - Arias-Loza, Paula Anahi
A1  - Kaspar, Mathias
A1  - Song, Moshi
A1  - Dorn, Gerald W.
A1  - Kohlhaas, Michael
A1  - Frantz, Stefan
A1  - Maack, Christoph
A1  - Gerull, Brenda
A1  - Dedkova, Elena N.
T1  - Mitofusin 2 is essential for IP3-mediated SR/Mitochondria metabolic feedback in ventricular myocytes
JF  - Frontiers in Physiology
N2  - Aim: Endothelin-1 (ET-1) and angiotensin II (Ang II) are multifunctional peptide hormones that regulate the function of the cardiovascular and renal systems. Both hormones increase the intracellular production of inositol-1,4,5-trisphosphate (IP\(_3\)) by activating their membrane-bound receptors. We have previously demonstrated that IP\(_3\)-mediated sarcoplasmic reticulum (SR) Ca\(^{2+}\) release results in mitochondrial Ca\(^{2+}\) uptake and activation of ATP production. In this study, we tested the hypothesis that intact SR/mitochondria microdomains are required for metabolic IP\(_3\)-mediated SR/mitochondrial feedback in ventricular myocytes.
Methods: As a model for disrupted mitochondrial/SR microdomains, cardio-specific tamoxifen-inducible mitofusin 2 (Mfn2) knock out (KO) mice were used. Mitochondrial Ca\(^{2+}\) uptake, membrane potential, redox state, and ATP generation were monitored in freshly isolated ventricular myocytes from Mfn2 KO mice and their control wild-type (WT) littermates.
Results: Stimulation of ET-1 receptors in healthy control myocytes increases mitochondrial Ca\(^{2+}\) uptake, maintains mitochondrial membrane potential and redox balance leading to the enhanced ATP generation. Mitochondrial Ca\(^{2+}\) uptake upon ET-1 stimulation was significantly higher in interfibrillar (IFM) and perinuclear (PNM) mitochondria compared to subsarcolemmal mitochondria (SSM) in WT myocytes. Mfn2 KO completely abolished mitochondrial Ca\(^{2+}\) uptake in IFM and PNM mitochondria but not in SSM. However, mitochondrial Ca2+ uptake induced by beta-adrenergic receptors activation with isoproterenol (ISO) was highest in SSM, intermediate in IFM, and smallest in PNM regions. Furthermore, Mfn2 KO did not affect ISO-induced mitochondrial Ca\(^{2+}\) uptake in SSM and IFM mitochondria; however, enhanced mitochondrial Ca\(^{2+}\) uptake in PNM. In contrast to ET-1, ISO induced a decrease in ATP levels in WT myocytes. Mfn2 KO abolished ATP generation upon ET-1 stimulation but increased ATP levels upon ISO application with highest levels observed in PNM regions.
Conclusion: When the physical link between SR and mitochondria by Mfn2 was disrupted, the SR/mitochondrial metabolic feedback mechanism was impaired resulting in the inability of the IP\(_3\)-mediated SR Ca\(^{2+}\) release to induce ATP production in ventricular myocytes from Mfn2 KO mice. Furthermore, we revealed the difference in Mfn2-mediated SR-mitochondrial communication depending on mitochondrial location and type of communication (IP\(_3\)R-mRyR1 vs. ryanodine receptor type 2-mitochondrial calcium uniporter).
KW  - mitofusin 2
KW  - IP3
KW  - SR/mitochondria metabolic feedback
KW  - mitochondrial mRyR1
KW  - ATP generation
KW  - endothelin-1
KW  - Mfn2 KO mice
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199141
SN  - 1664-042X
VL  - 10
IS  - 733
ER  - 
TY  - JOUR
A1  - Brodehl, Andreas
A1  - Pour Hakimi, Seyed Ahmad
A1  - Stanasiuk, Caroline
A1  - Ratnavadivel, Sandra
A1  - Hendig, Doris
A1  - Gaertner, Anna
A1  - Gerull, Brenda
A1  - Gummert, Jan
A1  - Paluszkiewicz, Lech
A1  - Milting, Hendrik
T1  - Restrictive cardiomyopathy is caused by a novel homozygous desmin (DES) mutation p.Y122H leading to a severe filament assembly defect
JF  - Genes
N2  - Here, we present a small Iranian family, where the index patient received a diagnosis of restrictive cardiomyopathy (RCM) in combination with atrioventricular (AV) block. Genetic analysis revealed a novel homozygous missense mutation in the DES gene (c.364T > C; p.Y122H), which is absent in human population databases. The mutation is localized in the highly conserved coil-1 desmin subdomain. In silico, prediction tools indicate a deleterious effect of the desmin (DES) mutation p.Y122H. Consequently, we generated an expression plasmid encoding the mutant and wildtype desmin formed, and analyzed the filament formation in vitro in cardiomyocytes derived from induced pluripotent stem cells and HT-1080 cells. Confocal microscopy revealed a severe filament assembly defect of mutant desmin supporting the pathogenicity of the DES mutation, p.Y122H, whereas the wildtype desmin formed regular intermediate filaments. According to the guidelines of the American College of Medical Genetics and Genomics, we classified this mutation, therefore, as a novel pathogenic mutation. Our report could point to a recessive inheritance of the DES mutation, p.Y122H, which is important for the genetic counseling of similar families with restrictive cardiomyopathy caused by DES mutations.
KW  - cardiovascular genetics
KW  - restrictive cardiomyopathy
KW  - desmin
KW  - intermediate filaments
KW  - desmin-related myopathy
KW  - cardiomyopathy
KW  - desminopathy
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193121
SN  - 2073-4425
VL  - 10
IS  - 11
ER  -