Background: Mutations in genes encoding intercalated disk/desmosome proteins, such as plakophilin 2 (PKP2), cause arrhythmogenic cardiomyopathy (ACM). Desmosomes are responsible for myocyte-myocyte attachment and maintaining mechanical integrity of the myocardium. Methods: We knocked down Pkp2 in HL-1 mouse atrial cardiomyocytes (HL-1Pkp2-shRNA) and characterized their biomechanical properties. Gene expression was analyzed by RNA-Sequencing, microarray, and qPCR. Immunofluorescence was used to detect changes in cytoskeleton and focal adhesion. Antagomirs were used to knock down expression of selected microRNA (miR) in the rescue experiments. Results: Knockdown of Pkp2 was associated with decreased cardiomyocyte stiffness and work of detachment, and increased plasticity index. Altered mechanical properties were associated with impaired actin cytoskeleton in HL-1Pkp2-shRNA cells. Analysis of differentially expressed genes identified focal adhesion and actin cytoskeleton amongst the most dysregulated pathways, and miR200 family (a, b, and 429) as the most upregulated miRs in HL-1Pkp2-shRNA cells. Knockdown of miR-200b but not miR-200a, miR-429, by sequence-specific shRNAs partially rescued integrin-α1 (Itga1) levels, actin organization, cell adhesion (on collagen), and stiffness. Conclusions: PKP2 deficiency alters cardiomyocytes adhesion through a mechanism that involves upregulation of miR-200b and suppression of Itga1 expression. These findings provide new insights into the molecular basis of altered mechanosensing in ACM.
Keywords: AFM; PKP2; arrhythmogenic cardiomyopathy; cell adhesion; focal adhesion; intercalated disk; microRNA.