Abstract 13400: Myopalladin Mutation Induced ERK1/2 and CARP/ANKRD1 Dysregulation in Restrictive Cardiomyopathy
Background: Restrictive cardiomyopathy (RCM) has a poor prognosis due to myocardial stiffness and fibrosis, particularly in children. Myopalladin (MYPN) is a nodal messenger molecule that transmits the Z-disk stretch-signaling to the nucleus in cardiomyocytes via its direct interaction with cardiac ankyrin repeat protein (CARP/ANKRD1). Previously, we reported that a nonsense Q529X-MYPN mutation caused familial RCM in humans and knock-in MYPNWT/Q529X mice in vivo. Mutant MYPNWT/Q529X mice displayed diminished MEK1/2, ERK1/2 phosphorylation and decreased CARP expression, with increased heart failure markers Nppa, Nppb and Myh species in the heart.
Objectives: This study sought to further delineate MEK1/2-ERK1/2 and CARP signaling in MYPNWT/Q529X mouse hearts.
Methods: All potential MEK1/2-associated proteins involved in fibrotic and hypertrophic remodeling in the heart were assessed using real-time PCR and Western blotting. Levels of CARP were quantified in whole hearts as well as in cytoplasmic and nuclear fractions of myocardial tissues. Immunoprecipitation, followed by pull-down, was performed in HEK293 cells after transient co-transfection of CARP-V5 and MYPN-GFP.
Results: In MYPNWT/Q529X hearts, MEK1/2-associated pathways involving p53, AKT, JNK, p38, FAK, STAT and Erb4 remained intact; only phosphorylation of SMAD2 was reduced, but total SMAD2 was normal. Reduction of nuclear CARP levels was concordant with reduced total CARP in mutant hearts. Although both MYPNWT and MYPNQ529X proteins retained binding to CARP, mutant MYPNQ529X failed to translocate to the nucleus unlike CARP or MYPNWT in vitro.
Conclusions: MYPN nuclear translocation appears to be regulated autonomously from MYPN-CARP association. In vivo, the Q529X-MYPN mutation caused decrease levels of total cardiac CARP as well as nuclear CARP, thus causing alterations in CARP-dependent heart failure gene expression. ERK1/2, CARP and SMAD2 pathways appear to be targets worth considering for RCM-specific therapy.
- © 2013 by American Heart Association, Inc.