Inhibiting PGGT1B Disrupts Function of RHOA, Resulting in T-cell Expression of Integrin α4β7 and Development of Colitis in Mice
Rocío López-Posadas 1, Petra Fastancz 2, Luz Del Carmen Martínez-Sánchez 2, Julia Panteleev-Ivlev 2, Veronika Thonn 2, Tatyana Kisseleva 2, Lukas S Becker 2, Anja Schulz-Kuhnt 2, Sebastian Zundler 2, Stefan Wirtz 2, Raja Atreya 2, Birgitta Carlé 3, Oliver Friedrich 3, Sebastian Schürmann 3, Maximilian J Waldner 2, Clemens Neufert 2, Cord H Brakebusch 4, Martin O Bergö 5, Markus F Neurath 2, Imke Atreya 2
Background & aims: It’s not obvious how regulating T-cell function is altered during growth and development of inflammatory bowel illnesses (IBD). We studied the mechanisms through which geranylgeranyltransferase-mediated prenylation controls T-cell localization towards the intestine and chronic inflammation.
Methods: We generated rodents with T-cell-specific disruption from the geranylgeranyltransferase type I, beta subunit gene (Pggt1b), known as Pggt1b|¡èCD4 rodents, or even the ras homolog member of the family A gene (Rhoa), known as Rhoa|¡èCD4 rodents. We studied rodents with knockout of CDC42 or RAC1 and wild-type rodents (controls). Intestinal tissues were examined by histology, multiphoton and confocal microscopy, and real-time polymerase squence of events. Activation of CDC42, RAC1, and RHOA were measured with G-LISA, cell fractionation, and immunoblots. T cells and lamina propria mononuclear cells from rodents were examined by flow cytometry or used in Rag1-/- rodents. Rodents received injections of antibodies against integrin alpha4beta7 or gavaged using the RORC antagonist GSK805. We acquired peripheral bloodstream and intestinal tissue samples from patients with and without IBD and examined them by flow cytometry.
Results: Pggt1b|¡èCD4 rodents developed spontaneous colitis, characterised by thickening from the intestinal wall, edema, fibrosis, accumulation of T cells within the colon, and elevated expression of inflammatory cytokines. In contrast to control CD4 T cells, PGGT1B-deficient CD4 T cells expressed considerably greater amounts of integrin alpha4beta7, which regulates their localization towards the intestine. Inflammation caused by change in PGGT1B-deficient CD4 T cells to Rag1-/- rodents was blocked by injection of the antibody against integrin alpha4beta7. Lamina propria of Pggt1b|¡èCD4 rodents had elevated figures of CD4 T cells that expressed RORC and greater amounts of cytokines created by T-assistant 17 cells (granulocyte-macrophage colony-stimulating factor, interleukin [IL]17A, IL17F, IL22, and tumor necrosis factor [TNF]). The RORC inverse agonist GSK805, although not antibodies against IL17A or IL17F, avoided colitis in Pggt1b|¡èCD4 rodents. PGGT1B-deficient CD4 T cells had decreased activation of RHOA. RhoA|¡èCD4 rodents were built with a similar phenotype to Pggt1b|¡èCD4 rodents, including growth and development of colitis, elevated figures of CD4 T cells in colon, elevated expression of integrin alpha4beta7 by CD4 T cells, and elevated amounts of IL17A along with other inflammatory cytokines in lamina propria. T cells isolated from intestinal tissues from patients with IBD had considerably ‘abnormal’ amounts of PGGT1B than tissues from individuals without IBD.
Conclusion: Lack of PGGT1B from T cells in rodents impairs RHOA function, growing CD4 T-cell expression of integrin alpha4beta7 and localization to colon, leading to elevated expression of inflammatory cytokines and colitis. T cells isolated from gut tissues from patients with IBD have ‘abnormal’ amounts of PGGT1B than tissues from patients without IBD.