IFNγ-induced suppression of ß-catenin signaling: evidence for roles of Akt and 14.3.3ζ.

The proinflammatory cytokine interferon γ (IFNγ ) influences intestinal epithelial cell (IEC) homeostasis in a biphasic manner by acutely stimulating proliferation that is followed by sustained inhibition of proliferation despite continued mucosal injury. ß-Catenin activation has been classically associated with increased IEC proliferation. However, we observed that IFNγ inhibits IEC proliferation despite sustained activation of Akt/ß-catenin signaling. Here we show that inhibition of Akt/ß-catenin-mediated cell proliferation by IFNγ is associated with the formation of a protein complex containing phosphorylated ß-catenin 552 (pß-cat552) and 14.3.3ζ. Akt1 served as a bimodal switch that promotes or inhibits ß-catenin transactivation in response to IFNγ stimulation. IFNγ initially promotes ß-catenin transactivation through Akt-dependent C-terminal phosphorylation of ß-catenin to promote its association with 14.3.3ζ. Augmented ß-catenin transactivation leads to increased Akt1 protein levels, and active Akt1 accumulates in the nucleus, where it phosphorylates 14.3.3ζ to translocate 14.3.3ζ/ß-catenin from the nucleus, thereby inhibiting ß-catenin transactivation and IEC proliferation. These results outline a dual function of Akt1 that suppresses IEC proliferation during intestinal inflammation.

Profiling retinal biochemistry in the MPDZ mutant retinal dysplasia and degeneration chick: a model of human RP and LCA.

PURPOSE: Raman microscopy, a rapid nondestructive technique that profiles the composition of biological samples, was used to characterize retinal biochemistry in the retinal dysplasia and degeneration (rdd) and wild-type (wt) chick retina during retinogenesis and at hatching. METHODS: Embryonic day (E)13 and posthatch day (P)1 rdd and wt retinal cross-sections (n = 3 of each line at each age) were profiled using 633 helium-neon laser excitation. The biochemical composition was determined using computational analysis of the Raman spectra. In parallel histology, TUNEL and glial fibrillary acidic protein (GFAP) immunostaining were used to visualize retinal dysfunction. RESULTS: Principal component (PC) analysis of the Raman spectra identified 50 major biochemical profiles, but only PCs that made significant contributions to variation within rdd and wt retina were mapped. These significant PCs were shown to arise from DNA, various fatty acids, melanin, and a number of proteins. Distinct patterns of GFAP immunostaining and a larger population of TUNEL-positive nuclei were observed in the rdd versus wt retina. CONCLUSIONS: This study has demonstrated that Raman microscopy can discriminate between major retinal biomolecules, thus providing an unbiased account of how their composition varies due to the impact of the MPDZ null mutation in the rdd chick relative to expression in the normal wt retina.