Elevating EGFR-MAPK program by a nonconventional Cdc42 enhances intestinal epithelial survival and regeneration

Area of Science:

• Gastroenterology and Molecular Biology
• Cellular and Molecular Physiology
• Regenerative Medicine

Background:

• The intestinal epithelium possesses remarkable regenerative capacity following injury, but the underlying regulatory mechanisms are not fully understood.
• Intestinal stem cells (ISCs) are vital for this regeneration, and their survival and function are critical.
• Previous research has not fully elucidated the specific molecular pathways governing ISC-mediated intestinal repair.

Purpose of the Study:

• To investigate the role of cell division control 42 (Cdc42) in intestinal stem cell survival and epithelial regeneration.
• To elucidate the molecular mechanisms by which Cdc42 influences intestinal repair, focusing on its interaction with the MAPK signaling pathway.
• To determine if enhancing the Cdc42-MAPK pathway can confer protection against mucosal injury.

Main Methods:

• Utilized ex vivo enteroid cultures to assess ISC survival and clonogenicity in the presence and absence of Cdc42.
• Employed proteomics and kinase analysis to identify Cdc42 variants and their signaling capabilities.
• Generated genetically engineered mice overexpressing Cdc42 variant 2 (Cdc42-V2) in the intestinal epithelium and ISCs.
• Assessed regenerative capacity and mucosal damage in response to genotoxic injury (irradiation) in engineered mice.

Main Results:

• Cdc42 is essential for ex vivo ISC survival and clonogenicity; Cdc42 deficiency leads to rapid apoptosis.
• Cdc42 engages with EGFR to promote EGF-stimulated endocytosis and MAPK signaling.
• A specific spliced variant, Cdc42-V2, demonstrates enhanced MAPK-activating capability.
• Overexpression of Cdc42-V2 in mice leads to elevated MAPK signaling, enhanced intestinal regeneration, and reduced radiation-induced mucosal damage.
• Targeted Cdc42-V2 overexpression in ISCs significantly improved intestinal regeneration after injury.

Conclusions:

• The intrinsic Cdc42-MAPK signaling program is a fundamental requirement for intestinal epithelial regeneration.
• Elevating the Cdc42-MAPK signaling cascade offers a protective mechanism against genotoxic injury to the intestinal epithelium.
• Cdc42-V2 represents a potential therapeutic target for enhancing intestinal repair and mitigating damage from treatments like radiation therapy.