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Transmembrane Forms (transmembrane + form)
Selected AbstractsA novel method of generating neuronal cell lines from gene-knockout mice to study prion protein membrane orientationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Andrea Holme Abstract The technology of gene knockout and transgenic mice has allowed the study of the role of genes and their proteins in animal physiology and metabolism. However, these techniques have often been found to be limited in that some genetic manipulations of mice led either to a fatal phenotype or to compensations that mask the loss of function of the target protein. The experimentation on neurons from transgenic mice is particularly critical in the study of key proteins that may be involved in neurodegeneration. The cell fusion technique has been implemented as a novel way to generate cell lines from prion protein knockout mice. Fusion between neonatal mouse neurons and a neuroblastoma cell line have led to a Prnp°/° cell line that facilitates the study of the knockout phenotype. These cells are readily transfectable and allowed us to study the expression of prion protein mutants on a PrP-knockout background. Using this cell line we have examined the effect of PrP mutations reported to alter PrPc to a transmembrane form. Our results suggest that these mutations do not create transmembrane forms of the protein, but block normal transport of PrP to the cell membrane. [source] Regulated expression of syndecan-4 in rat calvaria osteoblasts induced by fibroblast growth factor-2JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007Shu Jun Song Abstract Fibroblast growth factor-2 (FGF2) is a member of a prominent growth factor family that drives proliferation in a wide variety of cell types, including osteoblasts. The binding and signal transduction triggered by these mitogens is dependent on glycosaminoglycan (GAG) sugars, particularly of the heparan sulfate (HS) class. These are secreted in proteoglycan (PG) complexes, some of which become FGF co-receptors. The syndecans, the transmembrane forms of HSPG of which there are four members, act as multifunctional receptors for a variety of ligands involved in cell-extracellular matrix (ECM) adhesion as well as growth factor binding. To understand the role of syndecans in developing osteoblasts, the effects of exogenous FGF2 on syndecan expression were examined using primary rat calvarial osteoblasts. All four syndecan mRNAs were expressed in the osteoblasts, although only syndecan-4 was upregulated by FGF2 treatment in a dose-dependent manner. This upregulation could be abrogated by pretreatment with the protein synthesis inhibitor cycloheximide, suggesting that the upregulation of syndecan-4 by FGF2 is not a primary response. Osteoblast proliferation and mineralization were enhanced by exogenous FGF2 treatment, but could be specifically diminished by anti-syndecan-4 antibody pretreatment. This treatment also blocked FGF2-induced extracellular signal-regulated kinase activation, but not the expression of the bone-specific transcription factor Runx2. These results demonstrate that mitogen-triggered syndecan-4 expression is an intrinsic part of the pathways subtending osteoblast proliferation and mineralization. J. Cell. Biochem. 100: 402,411, 2007. © 2006 Wiley-Liss, Inc. [source] Soluble human p55 and p75 tumor necrosis factor receptors reverse spontaneous arthritis in transgenic mice expressing transmembrane tumor necrosis factor ,ARTHRITIS & RHEUMATISM, Issue 9 2006Carl K. Edwards III Objective The roles of the transmembrane and secreted forms of tumor necrosis factor , (TNF,) in rheumatoid arthritis (RA) remain unclear. Agents used to inhibit TNF, have shown varying efficacy in RA patients, suggesting that anti-TNF, agents possess dissimilar mechanisms of action, including the ability to neutralize transmembrane (tmTNF,) and secreted TNF,. In this study, TNF,-knockout (TNF,-KO) mice that were genetically altered to express elevated levels of tmTNF, were constructed to further understand the roles of the 17-kd secreted, trimeric, and 26-kd transmembrane forms of TNF,. Methods A speed-congenic mating scheme was used to generate 3 unique strains of mice: 1) transgenic tmTgA86 mice overexpressing 26-kd tmTNF, and also secreting 17-kd trimeric TNF, (tmTNF,-transgenic), 2) TNF,,/, mice (TNF,-KO), and 3) transgenic mice overexpressing tmTNF, backcrossed to TNF,-KO mice (tmTNF,-transgenic/TNF,-KO). Mice were treated with phosphate buffered saline (as vehicle control), dexamethasone (as positive control), or modified recombinant human soluble TNF receptor (sTNFR) p55 or p75, and were assessed clinically and histopathologically for signs of inflammation and development of arthritis. Results The tmTNF,-transgenic/TNF,-KO mice were born with crinkled tails and spinal deformities similar to those in ankylosing spondylitis. By 2,4 weeks, these mice developed symmetric inflammatory arthritis, characterized by tissue swelling, pannus formation, and bone deformities. The tmTNF,-transgenic mice also developed spontaneous-onset arthritis, but at a slower rate (100% incidence by 10,12 weeks). Clinical and histologic progression of arthritis in the tmTNF,-transgenic/TNF,-KO mice was reduced by treatment with dexamethasone or with the p55 or p75 sTNFR (69% and 63% reduction in total histologic score, respectively). Conclusion These data show that arthritis is sufficiently initiated and maintained in tmTNF,-transgenic/TNF,-KO mice, and that it can be neutralized by recombinant human p55 or p75 sTNFR, resulting in amelioration of the biologic and subsequent histologic destructive effects of tmTNF,. [source] | ||||||||||