The regulatory mechanisms enabling the intestinal epithelium to maintain a high degree of regenerative capacity during mucosal injury remain unclear. Ex vivo survival and clonogenicity of intestinal stem cells (ISCs) strictly required Cdc42-mediated growth response and Cdc42-deficient enteroids undergo rapid apoptosis. Mechanistically, Cdc42 engaging with EGFR was required for EGF-stimulated receptor-mediated endocytosis and sufficient to promote MAPK signaling. Proteomics and kinase analysis revealed that a physiological, but non-conventionally, spliced Cdc42 variant 2 (V2), exhibited stronger MAPK-activating capability. Human CDC42-V2 is transcriptionally elevated in some colon tumor tissues. Accordingly, mice engineered to overexpress Cdc42-V2 in intestinal epithelium showed elevated MAPK signaling, enhanced regeneration, and reduced mucosal damage in response to irradiation. Overproducing Cdc42-V2 specifically in mouse ISCs enhanced intestinal regeneration following injury. Thus, the intrinsic Cdc42-MAPK program is required for intestinal epithelial regeneration while elevating this signaling cascade is capable of initiating protection from genotoxic injury.
Xiao Zhang, Sheila Bandyopadhyay, Leandro P. Araujo, Kevin Tong, Juan Flores, Daniel Laubitz, Yanlin Zhao, George Yap, Jingren Wang, Qingze Zou, Ronaldo P. Ferraris, Lanjing Zhang, Wenwei Hu, Edward M. Bonder, Pawel R. Kiela, Robert J. Coffey, Michael Verzi, Ivaylo I. Ivanov, Nan Gao