Altered cytoskeleton signaling in cardiac disease determines defective cellular cargo internalization
Yuanyuan Dai1, Nadezda Ignatyeva1, Hang Xu1, Christof Lenz2, Henning Urlaub3, Stephan Lehnart1, Gerd Hasenfuss4, Antje Ebert1,5
1Department of Cardiology and Pneumology, Heart Research Center, University Medical Center Goettingen, Goettingen University, Göttingen, Germany,
2Institute of Clinical Chemistry, Proteomics Core, University Medical Center Goettingen, Göttingen, Germany,
3Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry Goettingen, Göttingen, Germany,
4Department of Cardiology and Pneumology, Heart Center, University Medical Center Goettingen, Göttingen, Germany,
5University Medical Center Goettingen, Goettingen University, Germany
Disturbed signal transduction from the cytoskeleton to the plasma membrane (PM) can cause severe disease, and its role in cardiac disease is incompletely understood. To study these signaling defects at the organelle but also nanoscale levels, we employed a human model of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Human iPSC-CMs carried inherited cardiac disease-specific mutations (MUT) in proteins of the sarcomere, a key functional component of the cytoskeleton in cardiomyocytes. We detected in MUT iPSC-CM patho-phenotypic signaling defects such as abnormal calcium handling and impaired contractile force transduction. Using this system in combination with isogenic CRISPR/Cas9 engineered controls, biochemical methods, and high-resolution STED imaging, we found disrupted interactions of sarcomeres with other cytoskeleton filaments and the PM in MUT iPSC-CMs. As a result, cargo internalization and endosome functions were found to be altered in MUT iPSC- CMs compared to WT controls. Of note, these defects were reversed in isogenic, mutation- corrected iPSC-CMs. Our studies showed these molecular signaling defects to be connected to disrupted sarcomere function in presence of cardiac disease-specific mutations. Chemical or genetic manipulation of these dysfunctions could, to different extend, reverse the observed defects. Moreover, we found that rescue of cargo internalization and altered endosome functions in MUT iPSC-CMs also recovered cardiomyopathy endpoint phenotypes such as sarcomere protein organization. Together, a better understanding of signaling defects in human cardiac disease models may reveal potential druggable targets for future therapeutic directions.