The class B scavenger receptor CD36, or fatty acid translocase (FAT), is an 88 kDa plasma membrane glycoprotein that is the founding member of the class B scavenger receptor family. It has a number of natural ligands and has different functions at various locations in the body. It contributes to adhesion of platelets via its binding to thrombospondin-1. In monocytes and macrophages, it contributes to recognition and phagocytosis of apoptotic cells and it mediates the binding and uptake of oxidatively damaged low-density lipoproteins (oxLDL). In adipose and muscle tissues, FAT/CD36 mediates high-affinity binding and uptake of long-chain fatty acids (LCFAs) and is therefore a key regulator of lipid storage (particularly in adipocytes) and mitochondrial beta oxidation (particularly in muscle). Interestingly FAT/CD36 also binds native lipoproteins (including high-density lipoproteins [HDL]) with high affinity in vitro, although the physiological significance of this is unclear at present. Expression of FAT/CD36 by hepatocytes has not been recognised until recently, mainly because it is gender-regulated in both humans, and rats. However, the primary function of FAT/CD36 in the liver is unknown. The work described in this thesis has used various transfected cell lines to examine the possibility that FAT/CD36 contributes to hepatic LCFA uptake and/or the uptake of cholesteryl esters (and other lipids) from HDL. The subcellular localization of FAT/CD36 has been explored in rat liver and in cell lines of hepatic and non-hepatic origin, especially with respect to its association with specialized plasma membrane lipid raft microdomains known as caveolae. Furthermore, the importance of the cytoplasmic carboxyl-terminus of FAT/CD36 in both subcellular localization of the molecule and its activity as a LCFA transporter has been examined using truncated mutants and chimeric variants of FAT/CD36. The results indicate that FAT/CD36 contributes to LCFA uptake by hepatocyte-derived cell lines. In these cells it resides in both non-raft and lipid raft domains of the plasma membrane that may not always include caveolae. The studies also indicate that the cytoplasmic C-terminus of FAT/CD36 contributes to the attachment of FAT/CD36 to membranes, including raft-derived detergent-resistant membranes. This domain is necessary also for correct targeting of the receptor to the plasma membrane and for its activity as a LCFA transporter. Finally, DNA constructs have been prepared and tested, with the objective of producing transgenic mice in which expression of FAT/CD36 can be induced and over-expressed specifically in the liver. This model could be used to confirm whether FAT/CD36 has a role as a LCFA transporter in the liver and to explore whether it has additional significance as a hepatic transporter of HDL-derived cholesteryl esters or as a scavenger of oxidised LDL. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294862 / Thesis (Ph.D.) -- School of Molecular and Biomedical Science, 2007

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

One of the most consistent biochemical changes associated with colon cancer progression is the altered expression of cell-associated carbohydrates. For example, the elevated expression of β1-6 branched N-linked oligosaccharides correlates with the presence of metastatic disease in colon cancer patients. Thus, it has become desirable to identify glycoproteins that are modified by these cancer-associated carbohydrates. Previous work in our laboratory identified the tumor-associated antigen 90 kDa (TAA90K) as a carrier of these cancer-associated carbohydrates. Since TAA90K has been previously implicated in cancer progression and metastasis, we examined its expression and function in human colon tumors. Immunohistochemical analysis revealed elevated expression of TAA90K in all tumor samples analyzed compared to normal colon. To examine the function of TAA90K in colon cancer, we performed protein binding and cellular assays with TAA90K purified from HT-29 human colon cancer cells infected with recombinant vaccinia virus expressing TAA90K. Purified TAA90K bound to ECM proteins including fibronectin, collagen IV, laminins-1, -5 and -10 and galectin-3. Unlike TAA90K isolated from other cell types, TAA90K isolated from HT-29 cells failed to mediate adhesion of colon cancer and normal cell lines, due in part to cell-specific glycosylation differences. Although TAA90K did not directly mediate cellular adhesion, it did modulate galectin-3-dependent adhesion of HT-29 cells. In addition, TAA90K bound to and was a substrate for MMP-7, a matrix metalloproteinase previously implicated in colon cancer progression. MMP-7-cleavage of TAA90K had little effect on its binding to pro- and active MMP-7, laminin-1 and galectin-3, but reduced significantly its binding to fibronectin and laminin-10. In addition, treatment of cells with MMP-7-cleaved TAA90K resulted in lower levels of proMMP-7 in the conditioned medium than cells treated with intact TAA90K. This may be mediated by the reduced binding of MMP-7-cleaved TAA90K to IL-6 and IL-1β, cytokines previously implicated in enhanced proMMP-7 expression in prostate cancer cells. Thus, a possible mechanism by which TAA90K may contribute to colon cancer progression is by modulating tumor cell adhesion to extracellular proteins and extracellular matrix remodeling through interactions with MMP-7 and galectin-3.

One of the most consistent biochemical changes associated with colon cancer progression is the altered expression of cell-associated carbohydrates. For example, the elevated expression of β1-6 branched N-linked oligosaccharides correlates with the presence of metastatic disease in colon cancer patients. Thus, it has become desirable to identify glycoproteins that are modified by these cancer-associated carbohydrates. Previous work in our laboratory identified the tumor-associated antigen 90 kDa (TAA90K) as a carrier of these cancer-associated carbohydrates. Since TAA90K has been previously implicated in cancer progression and metastasis, we examined its expression and function in human colon tumors. Immunohistochemical analysis revealed elevated expression of TAA90K in all tumor samples analyzed compared to normal colon. To examine the function of TAA90K in colon cancer, we performed protein binding and cellular assays with TAA90K purified from HT-29 human colon cancer cells infected with recombinant vaccinia virus expressing TAA90K. Purified TAA90K bound to ECM proteins including fibronectin, collagen IV, laminins-1, -5 and -10 and galectin-3. Unlike TAA90K isolated from other cell types, TAA90K isolated from HT-29 cells failed to mediate adhesion of colon cancer and normal cell lines, due in part to cell-specific glycosylation differences. Although TAA90K did not directly mediate cellular adhesion, it did modulate galectin-3-dependent adhesion of HT-29 cells. In addition, TAA90K bound to and was a substrate for MMP-7, a matrix metalloproteinase previously implicated in colon cancer progression. MMP-7-cleavage of TAA90K had little effect on its binding to pro- and active MMP-7, laminin-1 and galectin-3, but reduced significantly its binding to fibronectin and laminin-10. In addition, treatment of cells with MMP-7-cleaved TAA90K resulted in lower levels of proMMP-7 in the conditioned medium than cells treated with intact TAA90K. This may be mediated by the reduced binding of MMP-7-cleaved TAA90K to IL-6 and IL-1β, cytokines previously implicated in enhanced proMMP-7 expression in prostate cancer cells. Thus, a possible mechanism by which TAA90K may contribute to colon cancer progression is by modulating tumor cell adhesion to extracellular proteins and extracellular matrix remodeling through interactions with MMP-7 and galectin-3.

Thesis(Ph.D.)--Case Western Reserve University, 2009 / Title from PDF (viewed on 2009-12-30) Department of Chemistry Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Pharmacology and Pharmacy / Master / Master of Philosophy

The fetal-maternal interface is an immunologically privileged site where the semi-allogeneic fetus is protected from the maternal immune system. Macrophage represents the second major type (20-30%) of the decidual leukocyte. It functions as important regulator of pregnancy processes such as fetal tolerance, placental development and onset of labor. Changes in macrophage number and activity have been associated with fetal loss and pregnancy complications, including intrauterine growth restriction and preeclampsia. Glycodelin-A (Gd-A) is an abundant glycoprotein with ubiquitous distribution in the first trimester deciduas. It is suggested to be involved in early placental development by its regulatory activities on various immune cells. In this study, it is hypothesized that Gd-A has regulatory role in monocyte/macrophage functions and differentiation. The first objective examined the role of Gd-A in the biological activities of monocytes and macrophages. Gd-A was found to bind to the monocytic cell lines THP-1 and U937, blood monocytes, granulocyte macrophage colony-stimulating factor (GM-CSF)-differentiated macrophages, phorbol 12-myristate 13-acetate-differentiated macrophage and blood macrophages. Gd-A did not affect the viability, proliferation, cell death and phagocytic activity of monocytes and macrophages. The second objective examined the effect of Gd-A on the cytokine secretion of monocytes and macrophages. Gd-A treatment increased the IL-6 production in monocytes and macrophages. IL-6 was associated with the development and growth of the fetal-placental unit. Gd-A also induced the extracellular signal regulated kinases (ERK) activation. The involvement of ERK in stimulating IL-6 production was confirmed by using pharmacological inhibitors. Monocytes in the blood stream are attracted and residue into the deciduas, which differentiated into macrophage under the influence of various decidual soluble factors. Therefore, the third objective studied the possible involvement of Gd-A on the differentiation of monocytes into macrophages. Co-treatment of Gd-A during the GM-CSF-induced differentiation of monocytes stimulated the indoleamine 2,3-dioxygenase (IDO-1) expression and activity in differentiated macrophages. These differentiated macrophages inhibited the proliferation of autologous peripheral blood mononuclear cell in the co-culture system by G0/G1 cell cycle arrest. IDO-1 is one of the reported decidual macrophage markers. It has been suggested to be involved in establishing the tolerogenic environment during pregnancy through L-tryptophan depletion. The increase in IDO-1 expression may be regulated by PKC signaling pathway. Taken together, this thesis reported a novel role of Gd-A on the monocyte differentiation. The present results enhance our knowledge on the regulation of early placentation in human and may shed light on understanding the pathology of complicated pregnancy due to macrophage dysfunction. / published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

No description available.