The SRSF4–GAS5-Glucocorticoid Receptor Axis Regulates Ventricular Hypertrophy

Abstract

Rationale: RNA-binding proteins (RBPs) play critical roles in human biology and disease. Aberrant RBP expression affects various steps in RNA processing, altering the function of the target RNAs. The RBP serine/arginine-rich splicing factor 4 (SRSF4) has been linked to neuropathies and cancer. However, its role in the heart is completely unknown. Objective: To investigate the role of SRSF4 in the heart. Methods and Results: Echocardiography of mice specifically lacking SRSF4 in the heart (SRSF4 KO) revealed left ventricular hypertrophy and increased cardiomyocyte area, which led to progressive diastolic dysfunction with age. SRSF4 KO mice showed altered electrophysiological activity under isoproterenol-induced cardiac stress, with a post-QRS depression and a longer QT interval, indicating an elevated risk of sudden cardiac death. RNA-Seq analysis revealed expression changes in several long non-coding RNAs (lncRNAs), including GAS5 (growth arrest specific 5), which we identified as a direct SRSF4 target in cardiomyocytes by individual-nucleotide-resolution cross-linking and immuno-precipitation (iCLIP). GAS5 is a repressor of the glucocorticoid receptor (GR) and was downregulated in SRSF4 KO hearts. This corresponded with elevated GR transcriptional activity in cardiomyocytes, leading to increases in hypertrophy markers and cell size. Furthermore, hypertrophy in SRSF4 KO cardiomyocytes was reduced by overexpressing GAS5. Conclusions: Loss of SRSF4 expression results in cardiac hypertrophy, diastolic dysfunction, and abnormal repolarization. The molecular mechanism underlying this effect involves GAS5 downregulation and consequent elevation of GR transcriptional activity. Our findings may help to develop new therapeutic tools for the treatment of cardiac hypertrophy and myocardial pathology in Cushing's syndrome patients.

Stretching muscle cells induces transcriptional and splicing transitions and changes in SR proteins

“…In differentiated muscle cells, we observed that mechanosensitive genes after 3 h and 6 h of stretching encode proteins involved in steroid metabolism which is interesting considering the role of SRSF4 in steroid signaling in heart 64 . Further, mouse hearts lacking SRSF4 did not exhibit extensive splicing changes, but displayed increased SRSF6 protein in the myocardium suggesting that these two SR proteins may regulate similar targets in cardiac tissue 64 . Our study demonstrated an overlap between genes undergoing posttranscriptional transitions after stretching with the targets of SRSF4 or SRSF6 overexpression which suggests that these two RBPs may regulate similar splicing events.…”

“…In heart, SRSF4 promoted exon inclusion of the mechanosensitive cardiac troponin T gene 63 . Knockout of SRSF4 in mouse hearts led to ventricular hypertrophy and larger cardiomyocyte area along with alterations in glucocorticoid signaling 64 . In differentiated muscle cells, we observed that mechanosensitive genes after 3 h and 6 h of stretching encode proteins involved in steroid metabolism which is interesting considering the role of SRSF4 in steroid signaling in heart 64 .…”

“…Knockout of SRSF4 in mouse hearts led to ventricular hypertrophy and larger cardiomyocyte area along with alterations in glucocorticoid signaling 64 . In differentiated muscle cells, we observed that mechanosensitive genes after 3 h and 6 h of stretching encode proteins involved in steroid metabolism which is interesting considering the role of SRSF4 in steroid signaling in heart 64 . Further, mouse hearts lacking SRSF4 did not exhibit extensive splicing changes, but displayed increased SRSF6 protein in the myocardium suggesting that these two SR proteins may regulate similar targets in cardiac tissue 64 .…”

p38γ and p38δ regulate postnatal cardiac metabolism through glycogen synthase 1

“…For FS measurements, a long- or short-axis view of the heart was selected to obtain an M-mode registration in a line perpendicular to the left ventricular septum and the posterior wall at the level of the mitral chordae tendineae. Normal E/A ratios were established between 1.2 and 2 for contingency analysis [ 61 , 62 ].…”

A Novel Data-Driven Method for the Analysis and Reconstruction of Cardiac Cine MRI

“…The results and conclusions are presented in S 4 and S 6, respectively. Hearts from healthy 10 months-old mice (and SFSR4 wild-type mice [31]), were used. All the data have been obtained from previous studies performed in accor-dance with protocols approved by the CNIC's Institutional Animal Care and Research Advisory Committee of the Ethics Committee of the Regional Government of Madrid (PROEX177/17).…”