Desmosomes (DSMs) are intercellular junctions that anchor desmin-containing intermediate filaments (IF) at sites of cell-cell adhesion in cardiomyocyte (CM) intercalated discs. The importance of DSMs to cardiac function is highlighted by the existence of disorders including arrythmogenic cardiomyopathy and hypertrophic cardiomyopathy in which DSM mutations are associated with mechanical malfunctioning of the heart. While DSM¿s structural role in maintaining tissue integrity is well-established, my preliminary results provide evidence that DSMs actively contribute to mechanotransduction pathways that modulate CM contractile and signaling properties. We identified a novel interaction between the desmin IF-anchoring protein, desmoplakin (DP) and the RhoGEF Ect2, which localizes active RhoA at cell-cell junctions. RhoA is an upstream regulator of cellular processes including F-actin formation and contractility as well as transcriptional pathways. My results show that F-actin formation and CMs contractility are reduced in the absence of DP and/or Ect2, in a mechanosensitive manner. I propose that desmoplakin interaction with RhoGEF Ect2 acts as a scaffold to localize and activate the RhoGTPase RhoA, and that this mechanically sensitive signaling complex modulates F-actin filament formation, cell contractility and cell-cell force transmission in CMs. To address this hypothesis I will use shRNA adenovirus and CRISPR-Cas9 mediated gene-editing in neonatal rat ventricular cardiomyocytes and human iPSC-derived cardiomyocytes, respectively, and a cardiomyocyte-specific DP-deficient mice model to: 1) Determine the extent to which DP serves to position and regulate RhoA activity through the RhoGEF Ect2 in cardiomyocytes, and elucidate mechanosensitive signaling pathways mediated by the DP and Ect2, and 2) Determine the effect of mechanotransduction through DP/Ect2 on cardiomyocyte F-actin formation and contractility as well as cell-cell force transmission. These aims will be accomplished using state-of-the-art microscopical imaging, biochemical analysis and mechanobiological assays including traction force microscopy and atomic force microscopy. These studies will elucidate a novel function for DP in regulating cardiomyocyte mechanics and reveal its potential contribution in mechanical malfunctioning of heart in AC and other disorders associated with DP mutations and DSM remodeling.
|Effective start/end date||7/1/18 → 6/30/20|
- American Heart Association (18POST33960144)