Mutant Muscle LIM Protein C58G causes cardiomyopathy through protein depletion. (August 2018)

• Record Type: Journal Article
• Authors: Ehsan, Mehroz; Kelly, Matthew; Hooper, Charlotte; Yavari, Arash; Beglov, Julia; Bellahcene, Mohamed; Ghataorhe, Kirandeep; Poloni, Giulia; Goel, Anuj; Kyriakou, Theodosios; Fleischanderl, Karin; Ehler, Elisabeth; Makeyev, Eugene; Lange, Stephan; Ashrafian, Houman; Redwood, Charles; Davies, Benjamin; Watkins, Hugh; Gehmlich, Katja
• Is Part Of: Journal of molecular and cellular cardiology. Volume 121(2018)
• Page Start: 287
• Page End: 296
• Publication Date: 2018-08
• Subjects: Hypertrophic cardiomyopathy -- MLP C58G mutation -- Mouse knock-in model -- In vivo phenotyping -- RNAseq transcriptome analysis -- Protein depletion -- Proteasome -- Sarcomere; Cardiology -- Periodicals; Heart Diseases -- Periodicals; Molecular Biology -- Periodicals; Cardiologie -- Périodiques; Cardiology; Electronic journals; Periodicals; 616.12
• DOI: 10.1016/j.yjmcc.2018.07.248
• Languages: English
• ISSNs: 0022-2828

Abstract

Abstract: Cysteine and glycine rich protein 3 (CSRP3) encodes Muscle LIM Protein (MLP), a well-established disease gene for Hypertrophic Cardiomyopathy (HCM). MLP, in contrast to the proteins encoded by the other recognised HCM disease genes, is non-sarcomeric, and has important signalling functions in cardiomyocytes. To gain insight into the disease mechanisms involved, we generated a knock-in mouse (KI) model, carrying the well documented HCM-causing CSRP3 mutation C58G. In vivo phenotyping of homozygous KI/KI mice revealed a robust cardiomyopathy phenotype with diastolic and systolic left ventricular dysfunction, which was supported by increased heart weight measurements. Transcriptome analysis by RNA-seq identified activation of pro-fibrotic signalling, induction of the fetal gene programme and activation of markers of hypertrophic signalling in these hearts. Further ex vivo analyses validated the activation of these pathways at transcript and protein level. Intriguingly, the abundance of MLP decreased in KI/KI mice by 80% and in KI/+ mice by 50%. Protein depletion was also observed in cellular studies for two further HCM-causing CSRP3 mutations (L44P and S54R/E55G). We show that MLP depletion is caused by proteasome action. Moreover, MLP C58G interacts with Bag3 and results in a proteotoxic response in the homozygous knock-in mice, as shown by induction of Bag3 and associated heat shock proteins. In conclusion, the newly generated mouse model provides insights into the underlying disease mechanisms of cardiomyopathy caused by mutations in the non-sarcomeric protein MLP. Furthermore, our cellular experiments suggest that protein depletion and proteasomal overload also play a role in other HCM-causing CSPR3 mutations that we investigated, indicating that reduced levels of functional MLP may be a common mechanism for HCM-causing CSPR3 mutations. Highlights: We present a mouse model for non-sarcomeric hypertrophic cardiomyopathy (HCM). Homozygous Muscle LIM Protein (MLP) C58G mice have systolic and diastolic dysfunction. MLP C58G is depleted via proteasomal pathways. Protein depletion is also a hallmark of further HCM causing MLP mutations. MLP C58G interacts with Bag3 and causes a proteotoxic response.