Decreased Intranuclear Cardiac Troponin I Impairs Cardiac Autophagy through FOS/ATG5 in Ageing Hearts

Abstract Objective In our previous study, intranuclear cardiac troponin I (cTnI) was demonstrated may function as a co-factor of YY1. Here, we aimed to explore the role of intranuclear cTnI in ageing hearts. Methods and Results Nuclear translocation of cTnI was demonstrated by using Wester-blot and Immunofluorencence. The potential nucleolar localization sequences (NLSs) of cTnI were predicted by a web server, and then verified in 293t cells by putative NLS-eGFP-GST and NLS-mutant transfection. Ratio of Nuclear cTnI/ Total cTnI (Nu/T) decreased significantly in ageing hearts, accompanied with ATG5-decline related impaired cardiac autophagy. RNA sequencing was performed in cTnI knockout hearts. The differential expressed genes (DEGs) were analyzed by overlapping with YY1 ChIP sequencing data. Those filtered DEGs’ expression level were determined by cTnI gain and loss experiments in vitro. A strong correlation was found between expression patterns cTnI and FOS. By using ChIP-q-PCR we demonstrated specific binding DNA sequences of cTnI were enriched in FOS promoter − 299~-157 region. It was further verified that pcDNA3.1 (-)-cTnI could increase the promoter activity of FOS by using luciferase report assay. At last, we found that FOS can regulate ATG5 (autophagy related gene 5) gene by using luciferase report assay. Conclusion Taken together, our results indicate that decrease of intranuclear cTnI in ageing hearts may cause impaired cardiac autophagy through FOS/ATG5 pathway.