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Positive cross talk between protein kinase D and ?-catenin in intestinal epithelial cells: impact on ?-catenin nuclear localization and phosphorylation at Ser552.

ABSTRACT: Given the fundamental role of ?-catenin signaling in intestinal epithelial cell proliferation and the growth-promoting function of protein kinase D1 (PKD1) in these cells, we hypothesized that PKDs mediate cross talk with ?-catenin signaling. The results presented here provide several lines of evidence supporting this hypothesis. We found that stimulation of intestinal epithelial IEC-18 cells with the G protein-coupled receptor (GPCR) agonist angiotensin II (ANG II), a potent inducer of PKD activation, promoted endogenous ?-catenin nuclear localization in a time-dependent manner. A significant increase was evident within 1 h of ANG II stimulation (P< 0.01), peaked at 4 h (P< 0.001), and declined afterwards. GPCR stimulation also induced a marked increase in ?-catenin-regulated genes and phosphorylation at Ser(552) in intestinal epithelial cells. Exposure to preferential inhibitors of the PKD family (CRT006610 or kb NB 142-70) or knockdown of the isoforms of the PKD family prevented the increase in ?-catenin nuclear localization and phosphorylation at Ser(552) in response to ANG II. GPCR stimulation also induced the formation of a complex between PKD1 and ?-catenin, as shown by coimmunoprecipitation that depended on PKD1 catalytic activation, as it was abrogated by cell treatment with PKD family inhibitors. Using transgenic mice that express elevated PKD1 protein in the intestinal epithelium, we detected a marked increase in the localization of ?-catenin in the nucleus of crypt epithelial cells in the ileum of PKD1 transgenic mice, compared with nontransgenic littermates. Collectively, our results identify a novel cross talk between PKD and ?-catenin in intestinal epithelial cells, both in vitro and in vivo.

SUBMITTER: Wang J

PROVIDER: S-EPMC4824155 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND & AIMS:Mechanisms responsible for crypt architectural distortion in chronic ulcerative colitis (CUC) are not well understood. Data indicate that serine/threonine protein kinase Akt (Akt) signaling cooperates with Wingless (Wnt) to activate beta-catenin in intestinal stem and progenitor cells through phosphorylation at Ser552 (P-beta-catenin(552)). We investigated whether phosphoinositide 3-kinase (PI3K) is required for Akt-mediated activation of beta-catenin during intestinal inflammation. METHODS:The class IA subunit of PI3K was conditionally deleted from intestinal epithelial cells in mice named I-pik3r1KO. Acute inflammation was induced in mice and intestines were analyzed by biochemical and histologic methods. The effects of chemically blocking PI3K in colitic interleukin-10(-/-) mice were examined. Biopsy samples from patients were examined. RESULTS:Compared with wild-type, I-pik3r1KO mice had reduced T-cell-mediated Akt and beta-catenin signaling in intestinal stem and progenitor cells and limited crypt epithelial proliferation. Biochemical analyses indicated that PI3K-Akt signaling increased nuclear total beta-catenin and P-beta-catenin(552) levels and reduced N-terminal beta-catenin phosphorylation, which is associated with degradation. PI3K inhibition in interleukin-10(-/-) mice impaired colitis-induced epithelial Akt and beta-catenin activation, reduced progenitor cell expansion, and prevented dysplasia. Human samples had increased numbers of progenitor cells with P-beta-catenin(552) throughout expanded crypts and increased messenger RNA expression of beta-catenin target genes in CUC, colitis-associated cancer, tubular adenomas, and sporadic colorectal cancer, compared with control samples. CONCLUSIONS:PI3K-Akt signaling cooperates with Wnt to increase beta-catenin signaling during inflammation. PI3K-induced and Akt-mediated beta-catenin signaling are required for progenitor cell activation during the progression from CUC to CAC; these factors might be used as biomarkers of dysplastic transformation in the colon.

Project description:Maspin (SerpinB5) is a non-inhibitory serpin (serine protease inhibitor) with very diverse biological activities including regulation of cell adhesion, migration, death, control of gene expression and oxidative stress response. Initially described as a tumor and metastasis suppressor, clinical data brought controversies to the field, as some studies reported no correlation between SerpinB5 expression and prognosis value. These data underscore the importance of understanding SerpinB5 function in a normal physiological context and the molecular mechanism involved. Several SerpinB5 phosphoforms have been detected in different cell lines, but the signaling pathways involved and the biological significance of this post-translational modification in vivo remains to be explored. In this study we investigated SerpinB5 expression, subcellular localization and phosphorylation in different stages of the mouse mammary gland development and the signaling pathway involved. Here we show that SerpinB5 is first detected in late pregnancy, reaches its highest levels in lactation and remains at constant levels during post-lactational regression (involution). Using high resolution isoelectric focusing followed but immunoblot, we found at least 8 different phosphoforms of SerpinB5 during lactation, which decreases steadily at the onset of involution. In order to investigate the signaling pathway involved in SerpinB5 phosphorylation, we took advantage of the non-transformed MCF-10A model system, as we have previously observed SerpinB5 phosphorylation in these cells. We detected basal levels of SerpinB5 phosphorylation in serum- and growth factor-starved cells, which is due to amphiregulin autocrine activity on MCF-10A cells. EGF and TGF alpha, two other EGFR ligands, promote important SerpinB5 phosphorylation. Interestingly, EGF treatment is followed by SerpinB5 nuclear accumulation. Altogether, these data indicate that SerpinB5 expression and phosphorylation are developmentally regulated. In vitro analyses indicate that SerpinB5 phosphorylation is regulated by EGFR ligands, but EGF appears to be the only able to induce SerpinB5 nuclear localization.

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Positive cross talk between protein kinase D and ?-catenin in intestinal epithelial cells: impact on ?-catenin nuclear localization and phosphorylation at Ser552.

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