RhoGEF Ect2 supports RhoA activity at cell-cell junctions through desmoplakin

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Desmoplakin (DP) is a crucial desmosomal protein essential for tissue mechanical integrity.
• Mutations in DP are linked to diverse cardiocutaneous syndromes, highlighting its role beyond structural support.
• Emerging evidence suggests DP functions as a signaling hub, influencing cellular processes.

Purpose of the Study:

• To identify novel interaction partners of desmoplakin at intercellular junctions.
• To investigate the functional relationship between desmoplakin and regulators of the actin cytoskeleton.
• To explore the pathogenic mechanism of desmoplakin mutations in cardiocutaneous syndromes.

Main Methods:

• Immunofluorescence microscopy to visualize protein localization in keratinocytes and cardiomyocytes.
• Co-immunoprecipitation assays to confirm protein-protein interactions.
• Biochemical assays to measure RhoA activity.
• Analysis of patient-derived cells with desmoplakin mutations.

Main Results:

• The RhoGEF Ect2 was identified as a novel desmoplakin-associated protein at desmosomes and intercalated discs.
• Desmoplakin promotes Ect2 localization and maintains active RhoA (Rho-GTP) at cell junctions.
• Ect2 activity is regulated by PKC in a desmoplakin-dependent manner in cardiac myocytes.
• A truncated desmoplakin mutant found in Carvajal syndrome impairs Ect2 binding and localization.

Conclusions:

• Desmoplakin interacts with and recruits the RhoGEF Ect2 to cell junctions, regulating RhoA signaling.
• This interaction is critical for maintaining the integrity of desmosomes and intercalated discs.
• Impaired desmoplakin-Ect2 interaction due to mutations contributes to the pathogenesis of cardiocutaneous syndromes.