Abstract 19054: Yap Plays a Crucial Role in the Development of Cardiomyopathy in Lysosomal Storage Diseases
Lysosomal storage diseases (LSDs) cause severe cardiomyopathy. However, there is currently no effective treatment. Rag proteins play a critical role in regulating lysosomal functions. Muscle-specific deletion of RagA and RagB (RagA/B) suppresses autophagy and induces cardiomyopathy reminiscent of LSDs. Here, we aimed to investigate the molecular mechanism of cardiomyopathy in RagA/B knockout (KO) mice.
We generated cardiac-specific RagA/BKO (RagA/BcKO) mice using αMHC-Cre. Like the muscle-specific KO mice, RagA/BcKO mice showed prominent cardiac hypertrophy (CH) (heart weight (HW)/ tibial length (TL): 12.35 ± 0.41 vs. 7.12 ± 0.15, p< 0.01) at 3 months of age. RagA/BcKO mice exhibited significantly more phospho-histone H3-positive cardiomyocytes (CMs) than control mice, suggesting that CM proliferation is stimulated. However, RagA/BcKO mice exhibited a significantly smaller fractional shortening (%FS: 23.0 ± 0.82 vs. 45.8 ± 1.06, p< 0.01) and significantly higher mortality than control mice (50% vs. 0%, p<0.01). RagA/BcKO mouse hearts showed upregulation of βMHC and αsmooth muscle actin, indicating de-differentiation. Furthermore, RNA sequencing analysis revealed significant upregulation of several genes associated with Yes-associated protein (YAP), a key transcriptional target of the Hippo pathway that controls growth and survival. YAP also interacts with p62/SQSTM1, an LC3-adaptor protein, in the presence of chloroquine, which inhibits lysosomal function.
Indeed, YAP accumulated significantly more (5.9-fold, p<0.05) in RagA/BcKO-hearts, where autophagy is inhibited and p62/SQSTM1 is accumulated, than in control hearts. To elucidate the role of YAP in mediating cardiomyopathy, we crossed RagA/BcKO mice with cardiac-specific heterozygous YAPKO mice. Heterozygous deletion of YAP in RagA/BcKO mice reduced CH (HW/ TL: 9.12 ± 0.10 vs. 11.9 ± 0.27, p< 0.05) and improved cardiac function (%FS: 35.0 ± 2.89 vs. 24.0 ± 0.58, p< 0.05). Furthermore, pharmacological inhibition of YAP by verteporfin treatment also suppressed CH (HW/ TL: 8.92 ± 0.11 vs. 12.09 ± 0.30, p< 0.05) and heart failure (%FS: 33.3 ± 2.29 vs. 23.3 ± 0.63, p< 0.05) in RagA/BcKO mice. These results indicate that YAP is a novel therapeutic target for cardiomyopathy caused by LSDs.
Author Disclosures: S. Ikeda: None. A. Shirakabe: None. P. Zhai: None. J. Sadoshima: None.
- © 2016 by American Heart Association, Inc.