Cdc42GAP, reactive oxygen species, and the vimentin network

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Cdc42GAP (GTPase-activating protein) is involved in regulating cell functions like motility and apoptosis.
• Smooth muscle contraction involves dynamic cytoskeletal rearrangements, but the underlying molecular regulators are not fully understood.

Purpose of the Study:

• To investigate the role and regulation of Cdc42GAP in smooth muscle cells, particularly during contractile activation.
• To elucidate the molecular pathway through which Cdc42GAP influences the vimentin cytoskeleton and cell contraction.

Main Methods:

• Cloning and in vitro GTPase activity assays of Cdc42GAP.
• Development of an in vivo assay for Cdc42GAP activity in smooth muscle cells.
• Stimulation of smooth muscle cells with 5-hydroxytryptamine (5-HT) and assessment of Cdc42GAP activity, ROS levels, and downstream signaling.
• Retroviral expression of wild-type and mutant Cdc42GAP to evaluate effects on Cdc42 activation, PAK phosphorylation, vimentin phosphorylation, and cell contraction.

Main Results:

• Cdc42GAP enhanced Cdc42 GTP hydrolysis in vitro.
• 5-HT stimulation decreased Cdc42GAP activity in smooth muscle cells, a process mediated by reactive oxygen species (ROS).
• Expression of wild-type Cdc42GAP attenuated 5-HT-induced Cdc42 activation, PAK activation, vimentin phosphorylation, and smooth muscle contraction.

Conclusions:

• Cdc42GAP activity is suppressed by 5-HT stimulation through an ROS-dependent mechanism in smooth muscle cells.
• Cdc42GAP regulates the vimentin cytoskeleton and cell contraction via the Cdc42-PAK pathway during agonist stimulation.