PhD Scientific Days 2026

Poster Session 1.I - Theoretical and Translational Medicine

Ion-Dependent Modulation of Titin Proteolysis Reveals the Physiological Relevance of Short Titin forms

Name of the presenter

Balogh-Molnár, Andrea

Institute/workplace of the presenter

Semmelweis University, Department of Biophysics and Radiation Biology

Authors

Andrea Balogh-Molnár¹, Dr Hedvig Tordai¹, Dr Zsolt Mártonfalvi¹
1: Semmelweis University, Department of Biophysics and Radiation Biology

Text of the abstract

Introduction

Titin, the largest known human protein, spans from the Z-disk to the M-line and plays key structural and mechanical roles in the sarcomere, contributing to passive elasticity, integrity, and force transmission. In addition to full-length T1 titin, shorter T2 fragments are consistently observed in a muscle-specific ratio. Although T2 is generally considered a proteolytic product of T1, its physiological relevance remains unclear.

Aims
This study aimed to investigate post-mortem proteolysis of titin and determine whether this process can be modulated, thereby clarifying the origin and potential significance of T2 titin.

Methods
Whole muscle extracts from striated muscle samples were incubated under various conditions. Proteolysis was modulated using broad-spectrum protease inhibitors, chelating agents, and varying concentrations of calcium and zinc ions. Samples were analyzed by vertical agarose gel electrophoresis optimized for megadalton-sized proteins.

Results
Native muscles exhibited consistent, muscle-specific T1:T2 ratios in agreement with previous findings. Neither tissue excision nor homogenization altered this ratio. Proteolysis was strongly temperature-dependent, with increased degradation at 37°C compared to 4°C. Protease inhibitors and chelators partially reduced titin degradation, while near-complete inhibition was achieved in chemically skinned samples under specific conditions. In contrast, elevated calcium and zinc concentrations enhanced proteolysis.

Conclusion
These findings indicate that T2 titin is not merely an artifact of sample preparation but likely represents a naturally occurring form of titin. Its abundance appears regulated by ion-dependent proteolytic mechanisms, suggesting a potential physiological role in muscle function.