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Regulation of Secretion in Human Gallbladder Epithelial Cells
Published in Gianfranco Alpini, Domenico Alvaro, Marco Marzioni, Gene LeSage, Nicholas LaRusso, The Pathophysiology of Biliary Epithelia, 2020
Nicolas Chignard, Laura Fouassier, Annick Paul, Chantal Housset
Additional observations suggest that TCDC and TUDC, both regulate chloride secretion in this epithelium by means of two distinct mechanisms. In the absence of any other stimulus, they induce chloride secretion via calcium-dependent chloride channels. In addition, upon adenylyl cyclase stimulation by forskolin, they potentiate the production of cAMP, and increase chloride secretion via a cAMP-dependent pathway. This effect is mediated by PKC activation and subsequent stimulation of PKC-regulated isoforms of adenylyl cyclase26 (Fig. 4B). Given that TUDC induces lower mucin secretion than TCDC, the fact that TUDC shows similar potency as TCDC in stimulating chloride secretion both by a cAMP- dependent and -independent pathways, suggest that ursodeoxycholic acid may alter the ratio between mucin and hydro-electrolytic secretion in a direction that will increase bile fluidity.
Intestinal Chloride Secretion: Cyclic Amp and Ca2+ Interactions
Published in T. S. Gaginella, Regulatory Mechanisms — in — Gastrointestinal Function, 2017
Vincenzo Calderaro, Francesco Rossi
Activation of the cAMP-dependent pathway downmodulates PLC-γl activity. Targets of PKA actions responsible for the receptor-coupled PIP2 hydrolysis include the receptor, a G protein involved in coupling receptor function to PLC, and PLC itself.222 Likewise, the activation of PKC attenuates receptor-coupled PLC activity in certain type of cells, thus providing a negative feedback signal to limit the magnitude and duration of receptor signaling.219 This was also seen in T84 colonic cell cultures where long-term exposure to 400 μM phorbol 12,13-dibutyrate (PDB) brought about the uncoupling of phospholipase C from cholinergic and histaminergic receptors.223
The melanocyte and melaninogenesis
Published in Dimitris Rigopoulos, Alexander C. Katoulis, Hyperpigmentation, 2017
Dimitrios Xekardakis, Sabine Krueger-Krasagakis, Konstantinos Krasagakis
The process of melaninogenesis is regulated by a variety of pathways. The most important are the cyclic adenosine monophosphate (cAMP)–dependent and the protein kinase C (PKC)–dependent pathways, but additional pathways may also contribute to this process.8 The cAMP-dependent pathway modulates melaninogenesis by activating the protein kinase A (PKA), a serine/threonine kinase that consists of two catalytic and two regulatory subunits11 and phosphorylates several regulatory proteins, enzymes, and ion channels during this process.12 cAMP also modifies other pathways, like the phosphatidylinositol (PI) 3–kinase pathway, that ultimately serve to control melaninogenesis. PKC is a serine/threonine kinase that is activated by diacylglycerol and via its pathway induces phosphorylation of key proteins of melaninogenesis, such as tyrosinase. Additional pathways include those that increase intracellular cAMP levels, pathways that are activated by cyclic guanosine monophosphate (cGMP) and nitric oxide (NO), and the mitogen-activated protein kinase (MAPK)–related pathway, which phosphorylates proteins like microphthalmia-associated transcription factor (MITF).8,13,14
Subfatin and asprosin, two new metabolic players of polycystic ovary syndrome
Published in Journal of Obstetrics and Gynaecology, 2021
Rulin Deniz, Seyda Yavuzkir, Kader Ugur, Dondu Ulker Ustebay, Yakup Baykus, Sefer Ustebay, Suleyman Aydin
Recently, the most accused reasons in the etiopathogenesis of PCOS are peripheral insulin resistance and the resulting compensatory hyperinsulinemia (Rojas et al. 2014). When the cells are resistant to insulin, higher amounts of insulin are required for the intake of the same amount of glucose, and higher amounts of insulin are secreted by the pancreas (Sonne and Hemmingsen 2017). In the studies, it was reported that the concentration of asprosin of white fat tissue origin increased in the presence of insulin resistance (type II diabetes mellitus (T2DM, obesity) (Li et al. 2018; Zhang et al. 2019). Asprosin is encoded by the FBN1 gene as part of the protein profibrillin and separated from the C-terminus by specific proteolysis. This hormone activates glucose release from the liver by a cyclic adenosine monophosphate (cAMP) dependent pathway (Romere et al. 2016). Furthermore, asprosin can cross the blood-brain barrier and directly leads to orexigenic activity (Duerrschmid et al. 2017). In a study carried out with women with PCOS, the levels of asprosin were found to be statistically significantly higher compared to controls (Li et al. 2018; Alan et al. 2019); however, in another study, no significant difference was reported (Chang et al. 2019).
Proteomic characterization of the human lens and Cataractogenesis
Published in Expert Review of Proteomics, 2021
In contrast to the previously discussed modifications, reversible phosphorylation has been studied in depth in the lens with 2DGE, MS and/or extensive fractionation [44,47,118–123]. Proteins in the lens also undergo extensive phosphorylation. At least 271 proteins are phosphorylated at 855 sites and 54 proteins may be phosphorylated at least 5 times [44]. Reversible enzymatic phosphorylation of αA- and αB-crystallins occurs via a cAMP–dependent pathway, though autophosphorylation has also been reported [124]. Crystallin phosphorylation is pervasive with 35-50% of crystallin modified and phosphorylation identified in the lens shortly after birth [125]. The pathological role of lens phosphorylation has not been exhaustively studied in ARNC; however, phosphorylation of αA-crystallin and αB-crystallin subunit proteins increases in ARNC lenses and expression is stimulated by oxidative stress [119,126]. In lenses of different age, Gutierrez et al. showed that AQP0 and MP20 phosphorylation decreases across the barrier when established, but remains constant in lenses where the barrier is not established [47]. The pathological role of phosphorylated MP20 is not well established; however, AQP0 phosphorylation is known to increase channel water permeability [127]. Altogether, identification of PTMs and the resulting proteoforms, especially as they relate to lens fiber aging and cataractogenesis remains a significant challenge and opportunity in the lens community.
Oncoprotective Effects of Short-Chain Fatty Acids on Uterine Cervical Neoplasia
Published in Nutrition and Cancer, 2019
Madoka Matsuya-Ogawa, Toshiaki Shibata, Hiroaki Itoh, Hirotake Murakami, Chizuko Yaguchi, Kazuhiro Sugihara, Naohiro Kanayama
The concentration- and time-dependent suppression of HeLa cell proliferation by SCFA treatment and restoration of cell proliferation by cotreatment with GLPG0974, a specific antagonist of FFAR2, strongly supported the hypothesis that SCFAs exhibit oncoprotective effects via FFAR2. This is the first report of the usefulness of GLPG0974 in determining the specific contributions of FFAR2 to carcinogenesis (12). To our knowledge, few studies have examined the potential contributions of FFAR2 to neoplasia, and some of these studies have reported conflicting results. Similar oncoprotective effects were reported in colon cancer cells (17), MCF7 breast cancer cells (18), and BaF3 leukemia cells (19,20). Tang et al. reported that FFAR2 signaling activates apoptotic cell death by upregulating p21 in colon cancer cells after FFAR2 overexpression (17). Yonezawa et al. reported that FFAR2 signaling induced cell stress via p38 mitogen-activated protein kinase activation in MCF7 breast cancer cells (18). Bindels et al. revealed that FFAR2 suppressed cell proliferation of BaF3 leukemia cells transfected with Bcr-Abl mainly via a cAMP-dependent pathway (19). In contrast, Hatanaka et al. showed the enhancement of RAS-induced tumor growth in immunocompromised mice using NIH 3T3 fibroblasts overexpressing FFAR2 (21). They used different experimental models in various types of cancers because a standard experimental method has not been established for the analysis of the contribution of SCFA/FFAR2 pathways to carcinogenesis. Therefore, we speculate that SCFA/FFAR2 pathways may be associated with oncogenesis in an organ-specific manner. More extensive studies in various types of neoplasia are necessary to clarify the roles of SCFA/FFAR2 pathways in oncogenesis in humans.