The RhoGAP ARHGAP32 interacts with desmoplakin, and is required for desmosomal organization and assembly

Area of Science:

• Cell biology
• Biochemistry
• Tissue engineering

Background:

• Desmosomes are critical for tissue barrier integrity, especially in mechanically stressed tissues.
• The cytoskeleton regulates desmosome assembly, and desmosomes influence F-actin dynamics, but the precise mechanisms of this crosstalk are unknown.

Purpose of the Study:

• To elucidate the mechanisms underlying the crosstalk between desmosomes and the F-actin cytoskeleton.
• To identify proteins involved in regulating desmosome-actin interactions.

Main Methods:

• Immunofluorescence microscopy to visualize protein localization.
• Co-immunoprecipitation to study protein interactions.
• CRISPR/Cas9 gene editing to generate knockout cell lines (ARHGAP32-KO).
• Western blotting to assess protein phosphorylation and activity.

Main Results:

• ARHGAP32 localizes to desmosomes via interaction with desmoplakin (DSP).
• ARHGAP32 is essential for desmosome organization, maturation, and length.
• Loss of ARHGAP32 leads to increased F-actin stress fibers and actomyosin contractility.
• Inhibition of ROCK activity rescues desmosome organization in ARHGAP32-KO cells.
• DSP loss impairs ARHGAP32 localization and reduces actomyosin contractility.
• ARHGAP32 lacking its GAB2-interacting domain (GAB2-ID) fails to rescue desmosome organization.

Conclusions:

• ARHGAP32 regulates desmosomes through direct interaction with DSP.
• This interaction mediates crosstalk between desmosomes and the F-actin cytoskeleton.
• ARHGAP32 plays a key role in maintaining epithelial tissue integrity by linking desmosomes to actomyosin regulation.