The Mechanisms by Which RhoA Activity and Associated Synaptic Effects Are Controlled by the DISC1 Scaffolding-Like...

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• ARHGEF11 encodes PDZ-RhoGEF, a RhoA activator implicated in prefrontal cortex dysfunction and dendritic spine loss in bipolar disorder.
• DISC1 scaffolding protein directly binds PDZ-RhoGEF, suggesting a role in regulating its activity.
• Mechanisms by which DISC1 restricts PDZ-RhoGEF-mediated RhoA activation and impacts dendritic spine stability are not fully understood.

Purpose of the Study:

• To delineate the biochemical mechanisms by which DISC1 controls PDZ-RhoGEF's interaction with RhoA.
• To investigate how DISC1 regulates PDZ-RhoGEF's RhoA-activating function.
• To determine the impact of DISC1-PDZ-RhoGEF interaction on dendritic spine phenotypes.

Main Methods:

• Enzyme activity assays and protein domain mapping were used to identify DISC1's inhibitory mechanisms.
• Subcellular fractionation and viral-mediated gene transfer were employed to study DISC1's effects in vivo.
• Imaging and analysis were performed to assess dendritic spine morphology and stability.

Main Results:

• DISC1 inhibits PDZ-RhoGEF-mediated RhoA activation through two mechanisms: sequestering RhoA and reducing PDZ-RhoGEF catalytic activity.
• Disrupting the DISC1-PDZ-RhoGEF interaction significantly increases RhoA activation and leads to dendritic spine destabilization.
• In vivo knockdown of DISC1 elevated biochemical markers of RhoA activation.

Conclusions:

• Excessive PDZ-RhoGEF-mediated RhoA activation contributes to dendritic spine loss in bipolar disorder.
• DISC1's regulation of RhoA activation is a critical mechanism for maintaining dendritic spine stability.
• These findings offer potential translational insights into the pathophysiology of disease-related dendritic spine destabilization.