Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

General biochemistry --- 577.1 --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Biochemistry. --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- biochemie

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Biochemistry. --- 577.1 --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Biochemistry

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

577.1 --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Biogeography is the study of geographical variation in all characteristics of life, from genetic variation and differences in behaviour in species across regions, to geographic trends in diversity of whole communities. This book explains the key role played by geographical context in understanding the natural world.

577.1 --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Chemical bases of life. Biochemistry and bio-organic chemistry generally

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Het eerste deel van deze studie handelt over het gedrag van peroxisome proliferator-activated receptors (PPARs) in levende cellen. PPARs vormen een familie van nucleaire receptoren betrokken bij het vetzuur- en glucosemetabolisme, controle van inflammatie en wondheling. Er wordt eerst aangetoond dat, in tegenstelling tot de algemene kennis over deze eiwitten, date en groot percentage van de PPARs heterodimeriseren met de retinoid X receptor (RXR) in afwezigheid van ligand in levende cellen. De verrassend lage diffusiecoefficient die werd bekomen met fluorescentie correlatie spectroscopie suggereert dat alle receptoren deel uitmaken van een complex van hoge moleculaire massa en/of dat er een interactie is met relatief immobiele nucleaire structuren. PPARs worden niet geïmmobiliseerd na ligandbinding maar er wordt hier wel aangetoond dat de mobiliteit van de PPARs erdoor gemoduleerd wordt. Ze tonen een ligand-induceerde verkleining van de mobiliteit, waarschijnlijk door een veranderde interactie met cofactoren en/of chromatine. Deze studie toont aan dat coregulator rekrutering (en niet DNA-binding) een cruciale rol speelt bij receptor mobiliteit, wat suggereert dat transciptionele complexen gevormd worden vóór de binding aan de promotor. Daarenboven, de associatie van coactivators in afwezigheid van ligand in levende cellen, beide d.m.v. het N-terminale AB domein en door de AF-2 functie van het ligand bindend domein, voorziet een moleculaire basis om de constitutieve activiteit van PPARs te verklaren. The grote ligand-bindende pocket van de PPARs, die een grote variëteit aan liganden kan accomoderen, doet de vraag ontstaan of de PPAR activiteit en de PPAR-gereguleerde pathways zouden kunnen beïnvloed worden door de blootstelling aan endocriene verstorende chemicaliën. Deze studie toont aan hoe monoethyl-hexyl-phtalate (MEHP) op een directe manier PPARγ activeert en zo adipogenese promoot, zij het minder fel dan de volledige agonist rosiglitazone. In het tweede deel van dit werk wordt de cellulaire localisatie en mobiliteit van humaan biliverdine reductase (hBVR) bestudeerd. FCS werd gebruikt om de hBVR mobiliteit in levende cellen en om zijn functie in het nucleaire transport van hematine te bestuderen. In transiënt getransfecteerde HeLa cellen had enkel kinase-competent hBVR de mogelijkheid om naar de nucleus te transloceren. De volgende data suggereren de vorming van dynamische complexen van hBVR:hematine met het chromatine: a) verlaging van de mobiliteit van hBVR in heterochromatische regio’s is groter die in euchromatische regio’s in de aanwezigheid van hematine; b) de mobiliteit van hBVR in nucleaire lysaten die enkel oplosbare factoren bevatten is niet beinvloedt door hematine. Deze data suggereren dat hBVR, een kinase-afhankelijke transporter van hematine en een chromatine-bindend proteïne, essentieel is voor de regulatie van heme-responsive transcriptionele activiteit. The first part of the present study is focused into the study of the behavior in living cells of the peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors involved in lipid and glucose metabolism, inflammation control, and wound healing.It is here first demonstrated that, in contrast to a general assumption, a high percentage of PPARs readily heterodimerize with retinoid X receptor (RXR) in the absence of ligand in living cells.The surprisingly low PPAR diffusion coefficients derived from the fluorescence correlation spectroscopy (FCS) experiments suggest that all the receptors are engaged in complexes of very high molecular masses and/or interact with relatively immobile nuclear components.PPARs are not immobilized by ligand binding, but here it is shown that the diffusion of PPARs is modulated by ligand binding.They exhibit a ligand-induced reduction of mobility, probably due to enhanced interactions with cofactors and/or chromatin.However, this study reveals that coregulator recruitment(and not DNA binding) plays a crucial role in receptor mobility, suggesting that transcriptional complexes are formed prior to promoter binding.In addition, association with coactivators in the absence of a ligand in living cells, both through the N-terminal AB domain and the AF-2 function of the ligand binding domain, provides a molecular basis to explain PPARs constitutive activity.The large PPAR ligand binding pocket, which can accomodate a wide variety of ligands, raises the question of whether PPAR activity and PPAR-regulated pathways could be affected by exposure to endocrine disrupting chemicals.This study demonstrates how monoethyl-hexyl-phtalate (MEHP)directly activates PPARγ and promotes adipogenesis, albeit to a lower extent than the full agonist rosiglitazone. In the second part of the study the cellular localization and mobility of human biliverdin reductase (hBVR) is investigated.FCS was used to investigate hBVR mobility in living cells and its function in the nuclear transport of hematin.In transiently transfected HeLa cells only kinase competent hBVR translocates to the nucleus and hematin treatment of cells reduces its mobility in the nucleus.The following data suggest formation of hBVR:hematin dynamic complexes with chromatin: a) reduction of hBVR mobility in heterochromatin regions is greater than in euchromatin regions in presence of hematin; and b) hBVR mobility in nuclear lysates containing only soluble factors is not retarded by hematin. The data suggest that hBVR, as a kinase-dependent transporter of hematin and a chromatin binding protein, is esential to regulation of heme-responsive transcriptional activities. The present thesis is focused into the study of the behavior of two different proteins in living cells. A cell is divided in two big compartments: cytoplasm and nucleus.The two proteins studied here are: peroxisome proliferator-activated receptor and biliverdin reductase. The goals of the study were achieved by using techniques such as fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. The peroxisome proliferator-activated receptors are part of a big family of proteins named nuclear receptors and are associated with processes such as lipid and glucose metabolism, inflammation control, and wound healing. Peroxisome proliferator-activated receptors are also used for the treatment of hyperlipidemia and type 2 diabetes. This study brings new information about how PPARs behave in living cells and reveals the molecular mechanisms that dictate this behavior. Biliverdin reductase is a protein with a very complex behavior and it has different physiological functions in living cells.This protein was known to be localized only in cytoplasm, but recent studies have shown that in certain condition biliverdin reductase can be localized also in the nucleus of the cell. The present study brings new evidence about the nuclear localization of biliverdin reductase.Moreover, biliverdin reducatse is shown here to be involved in the transport from the cytoplasm to the nucleus of another molecule named hematin. The whole study is bringing new information about the cellular functions of the two mentioned proteins and is proving the usefulness of techniques like fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy in investigating proteins behavior in living cells.

Academic collection --- 577.1 --- 577.1 Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Chemical bases of life. Biochemistry and bio-organic chemistry generally --- Theses