MBFT XXIX. Kongresszus - 2023, Budapest .

Összes szerző

Kiss Balázs

az alábbi absztraktok szerzői között szerepel:

Bőcskei-Antal Barnabás Super-resolution investigation of liposomal nanosystems

Aug 29 - kedd

15:30 – 17:00

I. Poszterszekció

P06

Super-resolution investigation of liposomal nanosystems

Barnabás Bőcskei-Antal, Ádám Orosz, György Török, Balázs Kiss

Semmelweis University, Budapest, Department of Biophysics and Radiation Biology

Dynamic light scattering is a method used for a long time in the study of nano-sized lipid vesicles (~100 nm in diameter). Up until now, no imaging methodology has been used that directly reveals the inner structure of vesicles in this size range. However, the use of a method that makes the structure of nanovesicles visible under physiological conditions would have significant advantages in the planning and development of therapeutic use. Several research teams have already imaged liposomes using confocal microscopy, but this microscopic method does not have a sufficiently high resolution to enable a clear separation of the membrane and the internal fluid space. Our aim was to develop a methodology that the structure of liposomal systems can be visualized in a high-resolution, robust and reproducible manner.

For our work, small unilamellar vesicles produced from DPPC molecules were labeled with fluorescent (Alexa Fluor 594) lipopolysaccharide molecules, and this system was examined by dynamic light scattering and STED microscopy.

The diameter of the liposomes extruded through the 100 nm pore opening was found to be almost the same both during the light scattering measurement and in the confocal reconstruction images (~100‑110 nm). After finding the right DPPC/LPS ratio and finding the optimal STED settings, we managed to record images with a good signal-to-noise ratio. Through the deconvolution processing of the STED images, the internal aqueous phase of the liposomes can also be successfully explored.

Our research group previously dealt with photoreactive damage of the membranes. To test our methodology, we also followed this process using our developed STED approach.

DPPC – Dipalmitoylphosphatidylcholine
LPS – Lipopolysaccharide
STED – Stimulated Emission Depletion

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 Kellermayer^1,2,3,$, Hedvig Tordai^2,$, 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.

Török György Adaptive changes in the a-band region of the giant protein titin in diseased human cardiac sarcomere

Aug 30 - szerda

15:30 – 17:00

II. Poszterszekció

P32

Adaptive changes in the A-band region of the giant protein titin in diseased human cardiac sarcomere

György Török¹, Iliza Ramazanova¹, Péter Dániel¹, András Jámbor¹, Dalma Kellermayer^1,2, Cristina M. Șulea^1,2, Zoltán Szabolcs², Miklós S. Z. Kellermayer¹ and Balázs Kiss¹

¹Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary

²Heart and Vascular Center, Semmelweis University, Budapest, Hungary

Titin, the largest protein known, spans the half-sarcomere, the contractile unit of skeletal and cardiac muscle through its Z-disk to M-line and interacts with thin and thick filaments in the I- and A-band of the muscle sarcomere, respectively. Titin’s A-band segment is not well understood but is shown to be orders of magnitude less extensible than the I-band region of the molecule. Heterozygous truncating mutations (TTNtv) affecting A-band titin are often associated with dilated cardiomyopathy (DCM). Marfan syndrome (MFS), a connective tissue disorder caused by mutations of the matrix glycoprotein fibrillin is also associated with impaired cardiac contractility but its exact pathomechanism is largely unknown.

Here, we performed STED super-resolution microscopy on sections of stretched and fixed demembranated human cardiac myofibrils carrying heterozygous TTNtv mutations or on samples originated from MFS patients. Sequence-specific anti-titin antibodies included the 1) MIR, which labels titin at the ends of the thick filaments, 2) A170, labeling titin close to the M-line (this epitope is missing in TTNtv+). Sarcomere length-dependent anti-titin epitope position, shape and intensity analysis pointed at structural defects in the I/A junction and the M-band of TTNtv+ sarcomeres. Our experiments indicate that truncated titin is able to integrate into the cardiac sarcomere. We propose that the truncated titin cannot precisely register the ends of the thick filaments, and this can ultimately lead to the manifestation of DCM by disrupting the overlapping of thin and thick filaments. In MFS sarcomeres a pronounced, ~30 nm shift away from the M-line was found in the case of the A170 titin epitope suggesting that alterations in the M-band ultrastructure might be important contributors of the impaired cardiac contractility of MFS patients.