Gliadin Peptide P31-43 Induces mTOR/NFkß Activation and Reduces Autophagy: The Role of Lactobacillus paracasei CBA L74 Postbiotc.

Celiac disease (CD) is an autoimmune disease characterized by an altered immune response stimulated by gliadin peptides that are not digested and cause damage to the intestinal mucosa. The aim of this study was to investigate whether the postbiotic Lactobacillus paracasei (LP) could prevent the action of gliadin peptides on mTOR, autophagy, and the inflammatory response. Most of the experiments performed were conducted on intestinal epithelial cells Caco-2 treated with a peptic-tryptic digest of gliadin (PTG) and P31-43. Furthermore, we pretreated the Caco-2 with the postbiotic LP before treatment with the previously described stimuli. In both cases, we evaluated the levels of pmTOR, p70S6k, and p4EBP-1 for the mTOR pathway, pNFkß, and pERK for inflammation and LC 3 and p62 for autophagy. For autophagy, we also used immunofluorescence analysis. Using intestinal organoids derivate from celiac (CD) patients, we analyzed the effect of gliadin after postbiotic pretreatment with LP on inflammation marker NFkß. Through these experiments, we showed that gliadin peptides are able to induce the increase of the inflammatory response in a more complex model of intestinal epithelial cells. LP postbiotic was able to induce autophagy in Caco-2 cells and prevent gliadin effects. In conclusion, postbiotic pretreatment with LP could be considered for in vivo clinical trials.

Inflammation Is Present, Persistent and More Sensitive to Proinflammatory Triggers in Celiac Disease Enterocytes.

Celiac disease (CD) is a chronic inflammatory disease caused by a genetic predisposition to an abnormal T cell-mediated immune response to the gluten in the diet. Different environmental proinflammatory factors can influence and amplify the T cell-mediated response to gluten. The aim of this manuscript was to study the role of enterocytes in CD intestinal inflammation and their response to different proinflammatory factors, such as gliadin and viruses. Intestinal biopsies from CD patients on a gluten-containing (GCD-CD) or a gluten-free diet (GFD-CD) as well as biopsies from potential CD patients (Pot-CD) before the onset of intestinal lesions and controls (CTR) were used to investigate IL-1ß and IL-6 mRNA levels in situ. Organoids from CD patients were used to test the levels of NF-κB, ERK, IL-6, and IL-1ß by Western blot (WB), ELISA, and quantitative PCR. The Toll-like receptor ligand loxoribine (Lox) and gliadin peptide P31-43 were used as proinflammatory stimuli. In CD biopsies inflammation markers IL-1ß and IL-6 were increased in the enterocytes, and also in Pot-CD before the onset of the intestinal lesion and in GFD-CD. The inflammatory markers pNF-κB, pERK, IL-1ß, and IL-6 were increased and persistent in CD organoids; these organoids were more sensitive to P31-43 and Lox stimuli compared with CTR organoids. Taken together, these observations point to constitutive inflammation in CD enterocytes, which are more sensitive to inflammatory stimuli such as food components and viruses.

Proteolytic control of neurite outgrowth inhibitor NOGO-A by the cAMP/PKA pathway.

Protein kinase A (PKA) controls major aspects of neurite outgrowth and morphogenesis and plays an essential role in synaptic plasticity and memory. However, the molecular mechanism(s) of PKA action on neurite sprouting and activity are still unknown. Here, we report that in response to neurotrophin or cAMP stimulation the RING ligase praja2 ubiquitinates and degrades NOGO-A, a major inhibitor of neurite outgrowth in mammalian brain. Genetic silencing of praja2 severely inhibited neurite extension of differentiating neuroblastoma cells and mesencephalic neurons and axon outgrowth and sprouting of striatal terminals in developing rat brain. This phenotype was rescued when both praja2 and NOGO-A were depleted, suggesting that NOGO-A is, indeed, a biologically relevant target of praja2 in neuronal cells. Our findings unveil a novel mechanism that functionally couples cAMP signaling with the proteolytic turnover of NOGO-A, positively impacting on neurite outgrowth in mammalian brain.

PTPRK, an EGFR Phosphatase, Is Decreased in CeD Biopsies and Intestinal Organoids.

BACKGROUND & AIMS: Celiac disease (CeD) is an immune-mediated enteropathy triggered in genetically susceptible (HLA-DQ2/8) individuals by a group of wheat proteins and related prolamins from cereals. The celiac intestine is characterized by an inversion of the differentiation/proliferation program of the enterocytes, with an increase in the proliferative compartment and crypt hyperplasia, which are the mechanisms that regulate the increased proliferation in CeD that arenot completely understood.The aim of this study is to understand the role of Protein Tyrosine Phosphatase Receptor Type K (PTPRK), a nodal phosphatase that regulates EGFR activation in the proliferation of the enterocytes from CeD biopsies and organoids. METHODS: The levels of PTPRK were evaluated by RT PCR, western blot (WB) and immunofluorescence techniques in intestinal biopsies and organoids from CeD patients and controls. Additionally, pEGFR and pERK were evaluated by WB and proliferation by BrdU incorporation. PTPRK si-RNA was silenced in CTR organoids and was overexpressed in CeD organoids. RESULTS: PTPRK was reduced in Gluten Containing Diet-Celiac Disease (GCD-CeD) and Potential-Celiac Disease(Pot-CeD) biopsies (p < 0.01-p < 0.05) whereas pEGFR (p < 0.01 p < 0.01), pERK (p < 0.01 p < 0.01) and proliferation were increased. (p < 0.05 p < 0.05) respect to the controls.The CeD organoids reproduced these same alterations. Silencing of PTPRK in CTR organoids increased pEGFR, pERK and proliferation. The overexpression of PTPRK in CeD organoids reduced pEGFR, pERK and proliferation. CONCLUSIONS: modulation of PTPRK levels can reduce or increase pEGFR, pERK and proliferation in CeD or CTR organoids, respectively. The CeD organoids can be a good model to study the mechanisms of the disease.

PTPD1 supports receptor stability and mitogenic signaling in bladder cancer cells.

PTPD1, a cytosolic non-receptor protein-tyrosine phosphatase, stimulates the Src-EGF transduction pathway. Localization of PTPD1 at actin cytoskeleton and adhesion sites is required for cell scattering and migration. Here, we show that during EGF stimulation, PTPD1 is rapidly recruited to endocytic vesicles containing the EGF receptor. Endosomal localization of PTPD1 is mediated by interaction with KIF16B, an endosomal kinesin that modulates receptor recycling at the plasma membrane. Silencing of PTPD1 promotes degradation of EGF receptor and inhibits downstream ERK signaling. We also found that PTPD1 is markedly increased in bladder cancer tissue samples. PTPD1 levels positively correlated with the grading and invasiveness potential of these tumors. Transgenic expression of an inactive PTPD1 mutant or genetic knockdown of the endogenous PTPD1 severely inhibited both growth and motility of human bladder cancer cells. These findings identify PTPD1 as a novel component of the endocytic machinery that impacts on EGF receptor stability and on growth and motility of bladder cancer cells.

Author Correction: Constitutive alterations in vesicular trafficking increase the sensitivity of cells from celiac disease patients to gliadin.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Constitutive alterations in vesicular trafficking increase the sensitivity of cells from celiac disease patients to gliadin.

Celiac Disease (CD) is an autoimmune disease characterized by inflammation of the intestinal mucosa due to an immune response to wheat gliadins. Some gliadin peptides (e.g., A-gliadin P57-68) induce an adaptive Th1 pro-inflammatory response. Other gliadin peptides (e.g., A-gliadin P31-43) induce a stress/innate immune response involving interleukin 15 (IL15) and interferon α (IFN-α). In the present study, we describe a stressed/inflamed celiac cellular phenotype in enterocytes and fibroblasts probably due to an alteration in the early-recycling endosomal system. Celiac cells are more sensitive to the gliadin peptide P31-43 and IL15 than controls. This phenotype is reproduced in control cells by inducing a delay in early vesicular trafficking. This constitutive lesion might mediate the stress/innate immune response to gliadin, which can be one of the triggers of the gliadin-specific T-cell response.

Counterregulation of cAMP-directed kinase activities controls ciliogenesis.

The primary cilium emanates from the cell surface of growth-arrested cells and plays a central role in vertebrate development and tissue homeostasis. The mechanisms that control ciliogenesis have been extensively explored. However, the intersection between GPCR signaling and the ubiquitin pathway in the control of cilium stability are unknown. Here we observe that cAMP elevation promotes cilia resorption. At centriolar satellites, we identify a multimeric complex nucleated by PCM1 that includes two kinases, NEK10 and PKA, and the E3 ubiquitin ligase CHIP. We show that NEK10 is essential for ciliogenesis in mammals and for the development of medaka fish. PKA phosphorylation primes NEK10 for CHIP-mediated ubiquitination and proteolysis resulting in cilia resorption. Disarrangement of this control mechanism occurs in proliferative and genetic disorders. These findings unveil a pericentriolar kinase signalosome that efficiently links the cAMP cascade with the ubiquitin-proteasome system, thereby controlling essential aspects of ciliogenesis.

Mitochondrial AKAP1 supports mTOR pathway and tumor growth.

Mitochondria are the powerhouses of energy production and the sites where metabolic pathway and survival signals integrate and focus, promoting adaptive responses to hormone stimulation and nutrient availability. Increasing evidence suggests that mitochondrial bioenergetics, metabolism and signaling are linked to tumorigenesis. AKAP1 scaffolding protein integrates cAMP and src signaling on mitochondria, regulating organelle biogenesis, oxidative metabolism and cell survival. Here, we provide evidence that AKAP1 is a transcriptional target of Myc and supports the growth of cancer cells. We identify Sestrin2, a leucine sensor and inhibitor of the mammalian target of rapamycin (mTOR), as a novel component of the complex assembled by AKAP1 on mitochondria. Downregulation of AKAP1 impaired mTOR pathway and inhibited glioblastoma growth. Both effects were reversed by concomitant depletion of AKAP1 and sestrin2. High levels of AKAP1 were found in a wide variety of high-grade cancer tissues. In lung cancer, AKAP1 expression correlates with high levels of Myc, mTOR phosphorylation and reduced patient survival. Collectively, these data disclose a previously unrecognized role of AKAP1 in mTOR pathway regulation and cancer growth. AKAP1/mTOR signal integration on mitochondria may provide a new target for cancer therapy.