Effect of the Troponin I Restrictive Cardiomyopathy Mutation R145W on Protein Expression in Murine Murine Hearts

Abstract

Restrictive cardiomyopathy (RCM) is a relatively rare type of cardiomyopathy but is assocated with a high incidence of sudden cardiac death (SCD). The R145W mutation in troponin I have been shown to be associated with RCM and in patients with this mutation SCD has been found to occur. A transgenic mouse model of RCM expressing troponin I R145W showed increased calcium sensitivity of force development and impaired muscle relaxation. Isobaric tags for relative and absolute quantitation (iTRAQ), a non-gel-based technique used to quantify proteins from different sources in a single experiment, was used to determine the differences between hearts from 3 month old transgenic control mice (mice expressing human cardiac troponin I) and R145W mice (mice expressing human troponin I with the R145W mutation). Four hearts each from R145W and wild-type transgenic mice were proteomically investigated and several signaling pathways were found to be affected by the R145W mutation. Increases in enzymes involved in ATP production (such as NAD(P) transhydrogenase), kinases (calmodulin dependent protein kinase II beta), intermediate filament proteins (desmin), de-ribosylating enzyme (ADP-ribosylarginine hydrolase), proteolytic enzymes (tripeptidy peptides II), glycolytic enzymes (glyceraldehyde-3-phosphate dehydrogenase), and stress related proteins (inducible heat shock protein 90aa). At the proteolytic level the activity of the proteasome was decreased in hearts from R145W transgenic mice. No change in the protein expression levels of the 20S protein PSMA6 or the 19S protein Rpt1 was observed in these hearts. These results suggest that the RCM mutation R145W is associated with significant and complex changes in cardiac protein expression.