Cell Shedding Arrested in the Absence of GGTase-Prenylation Within IECs

Introduction: Epithelial integrity is essential for barrier function in the gut, contributing to the maintenance of tissue homeostasis. Such integrity needs continuous self-renewal of the epithelial layer, guaranteed by equilibrium of cell proliferation, migration, death and shedding. These processes require adjusted signaling pathways and cytoskeleton function in intestinal epithelial cells (IECs). In this context, Rho GTPases and their regulation by prenylation represent attractive candidates to be analyzed in vivo.

Methods: Conditional GGTase-I KO mice were generated by crossbreeding Pggt-Iβ^flx/flx and VillinCre-ERT2 mice. Pggt-Iβ^TiΔIEC mice were extensively analyzed in vivo and ex vivo.

Results: Deletion of the prenylation-enzyme GGTase-Iβ in IECs led to increased intestinal permeability and lethal enteric disease in mice. Our data support alteration of cell shedding and cytoskeleton remodeling as key mediator underlying this phenotype. Live imaging of the gut demonstrated that breakdown of barrier function (passage of topically applied rhodamine-dextran) went along with an accumulation of leakage points (epithelial gaps) and appearance of dextran-permeable IECs. The accumulation of arrested (early) versus completed (late) shedding events in Pggt-Iβ^TiΔIEC mice suggested an impaired completion of cell extrusion or arresting of cell shedding. Preliminary data suggested that LPS-induced pathological cell shedding does not contribute to the phenotype in Pggt-Iβ^TiΔIEC mice, and let us to speculate about the involvement of physiological cell shedding in GGTase-Iβ deficient epithelium.

Conclusions: Epithelial integrity depends on a sufficient level of GGTase-Iβ-mediated-prenylation within IECs. Lethal intestinal pathology in GGTase-Iβ deficient epithelium in mice is driven by arresting of cell shedding due to cytoskeleton remodeling.