| Clin Res Cardiol (2021). 10.1007/s00392-021-01933-9 |
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Abstract-Preis der Segnitz-Ackermann-Stiftung: |
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| N. J. Paulke1, S. Amlaz1, T. Kohl1, D. Kownatzki-Danger1, D. Uhlenkamp1, G. Hasenfuß1, S. E. Lehnart1, S. Brandenburg1, für die Studiengruppe: DZHK | ||
| 1Cellular Biophysics and Translational Cardiology Section, Heart Research Center Göttingen, University Medical Center Göttingen, Göttingen; | ||
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Introduction: The Ferlin protein family comprises transmembrane proteins with multiple C2 domains thought to be involved in vesicle fusion, trafficking, and membrane repair. Dysferlin may molecularly mediate different Ca2+-dependent membrane fusion and repair events in cardiomyocytes (CM), and Dysferlin deficiency was associated with cardiac dysfunction. Here we provide evidence for the critical involvement of Dysferlin in tubular membrane biogenesis and cellular remodelling in cardiac hypertrophy. Methods and Results: Among Ferlins, only Dysferlin and Myoferlin are abundantly expressed in CM as analysed by RNA sequencing. SDS-PAGE revealed that mouse ventricular myocytes (VM) predominantly express Dysferlin, whereas atrial myocytes showed 41% lower protein levels. Confocal and STimulated Emission Depletion (STED) nanoscopy spatially resolved the subcellular organization of Dysferlin in CM nanodomains through immunofluorescent staining and visualized punctual Dysferlin clusters next to and decorating the transverse-axial tubule system of isolated mouse and human CM. Dysferlin clusters were specifically localized at junctions of the tubular endomembrane system with the sarcoplasmic reticulum in nanometric proximity to RyR2 Ca2+ release units. Notably, complexome profiling (LC-MS/MS) found similar running behaviours for Dysferlin, RyR2 and L-type Ca2+ channels subunits, proposing protein-protein interactions in a high molecular weight complex. Moreover, we studied the remodelling and repair of the tubular endomembrane system by live-cell STED imaging in Dysferlin knockout (KO) mice and a mouse model of cardiac hypertrophy and heart failure induced by transaortic constriction (TAC). Untreated VM of KO mice presented with reduced network density and fewer network junctions, indicating a role for Dysferlin in proper tubule network formation. Unexpectedly, mortality four weeks post TAC was not increased in KO mice. In contrast, echocardiography revealed that Dysferlin deficiency prevents from left-ventricular hypertrophy in response to pressure overload. Analysis of single cell dimensions confirmed the absence of cellular hypertrophy in KO compared to wildtype VM (cell area: WT 3559 ± 120 µm2 vs. KO 2671 ± 87 µm2, n=163/158 VM, p<0.0001). Importantly, Dysferlin protein levels were significantly increased to 158% in wildtype VM post TAC. Since previous studies have shown that pressure-overload induced hypertrophy provokes a tubular network reorganization, we assumed Dysferlin to be involved in the de novo biogenesis of tubular membranes. Indeed, STED nanoscopy visualized highly abundant Dysferlin clusters that preferentially decorated newly shaped axial tubules in VM four weeks post TAC, which was quantified by subsequent component-specific tubule network analysis. While Dysferlin was mostly located at transverse tubule components in VM of sham-operated mice, VM four weeks post TAC showed Dysferlin primarily located at newly shaped axial tubule membranes. Conclusion: Our data indicate that Dysferlin may stabilize the cardiac tubule system and its junctions with the sarcoplasmic reticulum. Dysferlin is required for the de novo biogenesis of axial tubule membranes in differentiated CM, and pressure overload induced hypertrophic remodelling critically depends on the Dysferlin-mediated tubule network reorganization. Hence, Dysferlin may emerge as potential therapeutic approach to control the (sub)cellular membrane remodelling in cardiac diseases. |
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https://dgk.org/kongress_programme/ht2021/BS1016.htm |