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Genome-wide view on the physiology of vitamin D

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193493 Year: Pages: 194 DOI: 10.3389/978-2-88919-349-3 Language: English
Publisher: Frontiers Media SA
Subject: Physiology --- Science (General)
Added to DOAB on : 2016-03-10 08:14:32
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The main physiological actions of the biologically most active metabolite of vitamin D, 1a,25-dihydroxyvitamin D3(1a,25(OH)2D3), are calcium and phosphorus uptake and transport and thereby controlling bone formation. Other emergent areas of 1a,25(OH)2D3 action are in the control of immune functions, cellular growth and differentiation. This fits both with the widespread expression of the VDR and the above described consequences of vitamin D deficiency. Transcriptome-wide analysis indicated that per cell type between 200 and 600 genes are primary targets of vitamin D. Since most of these genes respond to vitamin D in a cell-specific fashion, the total number of vitamin D targets in the human genome is far higher than 1,000. This is supported by the genome-wide view on VDR binding sites in human lymphocytes, monocytes, colon and hepatic cells. All genomic actions of 1a,25(OH)2D3 are mediated by the transcription factor vitamin D receptor (VDR) that has been the subject of intense study since the 1980’s. Thus, vitamin D signaling primarily implies the molecular actions of the VDR. In this research topic, we present in 15 chapters different perspectives on the action of vitamin D and its receptor, such as the impact of the genomewide distribution of VDR binding loci, ii) the transcriptome- and proteome-wide effects of vitamin D, iii) the role of vitamin D in health, iv) tissue-specific functions of vitamin D and v) the involvement of vitamin D in different diseases, such as infections, autoimmune diseases, diabetes and different types of cancer.

T Cell Regulation by the Environment

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197330 Year: Pages: 115 DOI: 10.3389/978-2-88919-733-0 Language: English
Publisher: Frontiers Media SA
Subject: Allergy and Immunology --- Medicine (General)
Added to DOAB on : 2016-04-07 11:22:02
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Naïve T cells get activated upon encounter with their cognate antigen and differentiate into a specific subset of effector cells. These T cells are themselves plastic and are able to re-differentiate into another subset, changing both phenotype and function. Differentiation into a specific subset depends on the nature of the antigen and of the environmental milieu. Notably, certain nutrients, such as vitamins A and D, sodium chloride, have been shown to modulate T cell responses and influence T cell differentiation. Parasite infection can also skew Th differentiation. Similarly, the gut microbiota regulates the development of immune responses. Lastly, the key role of metabolism on T cells has also been demonstrated. This series of articles highlights some of the multiple links existing between environmental factors and T cell responses.

Lipid Signaling in T Cell Development and Function

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196975 Year: Pages: 142 DOI: 10.3389/978-2-88919-697-5 Language: English
Publisher: Frontiers Media SA
Subject: Medicine (General) --- Allergy and Immunology
Added to DOAB on : 2016-08-16 10:34:25
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Lipids are best known as energy storing molecules and core-components of cellular membranes, but can also act as mediators of cellular signaling. This is most prominently illustrated by the paramount importance of the phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K) signaling pathways in many cells, including T cells and cancer cells. Both of these enzymes use the lipid phosphatidylinositol(4,5)bisphosphate (PIP2) as their substrate. PLCs produce the lipid product diacylglycerol (DAG) and soluble inositol(1,4,5)trisphosphate (IP3). DAG acts as a membrane tether for protein kinase C and RasGRP proteins. IP3 is released into the cytosol and controls calcium release from internal stores. The PI3K lipid product phosphatidylinositol(3,4,5)trisphosphate (PIP3) controls signaling by binding and recruiting effector proteins such as Akt and Itk to cellular membranes. Recent research has unveiled important signaling roles for many additional phosphoinositides and other lipids. The articles in this volume highlight how multiple different lipids govern T cell development and function through diverse mechanisms and effectors. In T cells, lipids can orchestrate signaling by organizing membrane topology in rafts or microdomains, direct protein function through covalent lipid-modification or non-covalent lipid binding, act as intracellular or extracellular messenger molecules, or govern T cell function at the level of metabolic regulation. The cellular activity of certain lipid messengers is moreover controlled by soluble counterparts, exemplified by symmetric PIP3/inositol(1,3,4,5)tetrakisphosphate (IP4) signaling in developing T cells. Not surprisingly, lipid producing and metabolizing enzymes have gained attention as potential therapeutic targets for immune disorders, leukemias and lymphomas.

Keywords

Lipid --- T cell --- eicosanoid --- PI3K --- Vitamin D --- diacylglyerol --- Inositol --- Pten --- SHIP --- Adipokine

Physiology and Pathophysiology of the Extracellular Calcium-Sensing Receptor

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889455126 Year: Pages: 189 DOI: 10.3389/978-2-88945-512-6 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Physiology
Added to DOAB on : 2019-01-23 14:53:42
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Calcium is vital for human physiology; it mediates multiple signaling cascades, critical for cell survival, differentiation, or death both as first and as second messenger. The role of calcium as first messenger is mediated by the G-protein coupled receptor, the extracellular calcium-sensing receptor (CaSR). The CaSR is a multifaceted molecule that senses changes in the concentration of a wide variety of environmental factors including di- and trivalent cations, amino acids, polyamines, and pH. In calcitropic tissues with obvious roles in calcium homeostasis such as parathyroid, kidney, and bone it regulates circulating calcium concentrations. The germline mutations of the CaSR cause parathyroid disorders demonstrating the importance of the CaSR for the maintenance of serum calcium homeostasis. The CaSR has an important role also in a range of non-calcitropic tissues, such as the intestine, lungs, central and peripheral nervous system, breast, skin and reproductive system, where it regulates molecular and cellular processes such as gene expression, proliferation, differentiation and apoptosis; as well as regulating hormone secretion and lactation.This Research Topic is an overview of the CaSR and its molecular signaling properties together with the various organ systems where it plays an important role. The articles highlight the current knowledge regarding many aspects of the calcitropic and non-calcitropic physiology and pathophysiology of the CaSR.

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