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Kellermayer MIklós
Truncated titin is integrated into the human dilated cardiomyopathic sarcomere

Aug 29 - kedd

08:30 – 08:50

Molekuláris biofizika

E01

Truncated titin is integrated into the human dilated cardiomyopathic sarcomere

Dalma Kellermayer1,2,3,$, Hedvig Tordai2,$, Balázs Kiss2, György Török2, Dániel M. Péter2, Alex Ali Sayour1, Miklós Pólos1, István Hartyánszky1, Bálint Szilveszter1, Siegfried Labeit4, Ambrus Gángó3, Gábor Bedics3, Csaba Bödör3, Tamás Radovits1, Béla Merkely1 and Miklós S.Z. Kellermayer2

1Heart and Vascular Center, Semmelweis University, Budapest, Hungary

2Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary

31st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary

4DZHK Partnersite Mannheim-Heidelberg, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany

Heteroyzgous truncating mutations in the TTN gene (TTNtv) encoding the giant protein titin are the most common genetic cause of dilated cardiomyopathy (DCM). However, the molecular mechanisms by which TTNtv mutations induce DCM are controversial. Here we investigated 118 clinically identified DCM human cardiac samples with next-generation sequencing, high-resolution gel electrophoresis, Western blot analysis and super-resolution microscopy in order to dissect the structural and functional consequences of TTNtv mutations. The occurrence of TTNtv was found to be 15% in the DCM cohort. Truncated titin proteins matching, by molecular weight, the gene-sequence predictions were detected in the majority of the TTNtv samples. The total amount of expressed titin, which includes the truncated fragments, was comparable in the TTNtv+ and TTNtv- samples, indicating that titin haploinsufficiency may not be the leading cause of the molecular pathogenesis. Proteomic analysis of washed cardiac myofibrils and STED super-resolution microscopy of myocardial sarcomeres labeled with sequence-specific anti-titin antibodies revealed that truncated titin is structurally integrated in the sarcomere. Sarcomere length-dependent anti-titin epitope position, shape and intensity analysis pointed at structural disarrangements in the I/A junction and the M-band of TTNtv+ sarcomeres, which may play a role, via faulty mechanosensor function, in the development of manifest DCM.

Acknowledgments

This research was funded by the ÚNKP-19-3-I New National Excellence Program of The Ministry for Innovation and Technology to D.K. and grants from the Hungarian National Research, Development and Innovation Office (K135360 to M.K., FK135462 to B.K., K135076 to B.M., Project no. NVKP_16-1–2016-0017 ’National Heart Program’, and the 2020-1.1.6-JÖVŐ-2021-00013 grant) and the Thematic Excellence Programme (2020-4.1.1.-TKP2020) of the Ministry for Innovation and Technology in Hungary, within the framework of the Therapeutic Development and Bioimaging thematic programs of Semmelweis University.