Lysyl oxidase (LOX), an amine oxidase critical for the initiation of collagen and elastin cross-linking, has recently been shown to regulate cellular activities possibly by modulating the functions of growth factors. In this study, we investigated the interaction between LOX and transforming growth factor-beta1 (TGF-beta1), a potent growth factor abundant in bone, the effect of LOX on TGF-beta1 signaling, and its potential mechanism. The specific binding between mature LOX and mature TGF-beta1 was demonstrated by immunoprecipitation and glutathione S-transferase pulldown assay in vitro. Both proteins were colocalized in the extracellular matrix in an osteoblastic cell culture system, and the binding complex was identified in the mineral-associated fraction of bone matrix. Furthermore, LOX suppressed TGF-beta1-induced Smad3 phosphorylation likely through its amine oxidase activity. The data indicate that LOX binds to mature TGF-beta1 and enzymatically regulates its signaling in bone and thus may play an important role in bone maintenance and remodeling.
"Lysyl oxidase enzyme has also been implicated in activating FAK signaling, though the functional substrates in this context have not been identified , . Lysyl oxidase has been reported to oxidize and inactivate the functions of FGF-2 and TGF-β by direct enzymatic modification , . Although FGF-2 and TGF-β are each mitogenic for mesenchymal cells, oxidation and inactivation of posttranslational activators of latent TGF-β or of FGF co-receptors could lead to a positive role for lysyl oxidase in stimulating cell proliferation , . "
[Show abstract][Hide abstract] ABSTRACT: Lysyl oxidase is a multifunctional enzyme required for collagen biosynthesis. Various growth factors regulate lysyl oxidase during osteoblast differentiation, subject to modulation by cytokines such as TNF-α in inflammatory osteopenic disorders including diabetic bone disease. Canonical Wnt signaling promotes osteoblast development. Here we investigated the effect of Wnt3a and TNF-α on lysyl oxidase expression in pluripotent C3H10T1/2 cells, bone marrow stromal cells, and committed osteoblasts. Lysyl oxidase was up-regulated by a transcriptional mechanism 3-fold in C3H10T1/2 cells, and 2.5-fold in bone marrow stromal cells. A putative functional TCF/LEF element was identified in the lysyl oxidase promoter. Interestingly, lysyl oxidase was not up-regulated in committed primary rat calvarial- or MC3T3-E1 osteoblasts. TNF-α down-regulated lysyl oxidase both in Wnt3a-treated and in non-treated C3H10T1/2 cells by a post-transcriptional mechanism mediated by miR203. Non-differentiated cells do not produce a collagen matrix; thus, a novel biological role for lysyl oxidase in pluripotent cells was investigated. Lysyl oxidase shRNAs effectively silenced lysyl oxidase expression, and suppressed the growth of C3H10T1/2 cells by 50%, and blocked osteoblast differentiation. We propose that interference with lysyl oxidase expression under excess inflammatory conditions such as those that occur in diabetes, osteoporosis, or rheumatoid arthritis can result in a diminished pool of pluripotent cells which ultimately contributes to osteopenia.
PLoS ONE 06/2014; 9(6):e100669. DOI:10.1371/journal.pone.0100669 · 3.23 Impact Factor
"r organization of the ECM may lead to altered adhesive properties of chondrogenic progenitor cells , which can impair differentiation of chondrocytes and subsequent maturation of cartilage elements ( Lang et al . , 2006 ) . It is worth noting that recent research has also demonstrated that LOX can directly and indirectly modify TGF - b1 activity ( Atsawasuwan et al . , 2008 ; Levental et al . , 2009 ) . Taken together , lysyl oxidase – like proteins are excellent candidates for further investigations in the molecular mechanisms of DTC - induced bone and cartilage defects ."
[Show abstract][Hide abstract] ABSTRACT: Dithiocarbamates (DTCs) have a wide variety of applications in diverse fields ranging from agriculture to medicine. DTCs are teratogenic to vertebrates but the mechanisms by which they exert these effects are poorly understood. Here, we show that low nanomolar exposure to three DTCs, tetraethylthiuram (thiram), tetramethylthiuram (disulfiram), and sodium metam (metam), leads to craniofacial abnormalities in developing zebrafish embryos that are reminiscent of DTC-induced abnormalities found in higher vertebrates. In order to better understand the molecular events underlying DTC teratogenesis, we exposed embryonic zebrafish (PAC2) cells to thiram and disulfiram and measured changes in gene expression with microarrays. We found differential expression of 166 genes that were specific for exposure to DTCs and identified a network of genes related to connective tissue development and function. Additionally, we found eight downregulated genes related to transforming growth factor beta-1 (TGF-beta1) signaling, including an essential transcription factor for zebrafish craniofacial development, SRY-box-containing gene 9a (sox9a). Finally, we show that sox9a expression is perturbed in the ceratobranchial arches of DTC-exposed zebrafish, suggesting that this is an important event in the development of DTC-induced craniofacial abnormalities. Together, we provide evidence for a novel teratogenic endpoint and a molecular basis for a better understanding of DTC-induced teratogenesis in vertebrates.
"Lysine tyrosylquinone (LTQ) is present in an other copper-depending amine oxidase, lysyl oxidase (LOX) selectively inhibited by b-aminopropionitrile. Lysyl oxidase catalyzes the oxidation of specific lysine residues within extracellular elastin and collagen thus generating residues of a-aminoadipic-d-semialdehyde within these proteins. This enzyme (LOX) has been implicated, among several other pathological conditions, in lathyrism and in a number of novel biological functions, including the regulation of the promoter activity of collagen type III, the control of cell adhesion and growth, the metastatic phenotype of certain tumors in adult animals and gene regulation (Lucero et al. 2008; Atsawasuwan et al. 2008). Polyamine oxidation and catalytic mechanisms of Cu-amine oxidases The widespread occurrence of AOs in different organisms and organs suggests their undoubtedly relevant biological Anticancer activity of polyamine enzymatic oxidation products 357 function in biogenic amine metabolism. "
[Show abstract][Hide abstract] ABSTRACT: The polyamines spermine, spermidine and putrescine are ubiquitous cell components. These molecules are substrates of a class of enzymes that includes monoamine oxidases, diamine oxidases, polyamine oxidases and copper-containing amine oxidases. Amine oxidases are important because they contribute to regulate levels of mono- and polyamines. In tumors, polyamines and amine oxidases are increased as compared to normal tissues. Cytotoxicity induced by bovine serum amine oxidase (BSAO) and spermine is attributed to H(2)O(2) and aldehydes produced by the reaction. This study demonstrated that multidrug-resistant (MDR) cancer cells (colon adenocarcinoma and melanoma) are significantly more sensitive than the corresponding wild-type (WT) ones to H(2)O(2) and aldehydes, the products of BSAO-catalyzed oxidation of spermine. Transmission electron microscopy (TEM) observations showed major ultrastructural alterations of the mitochondria. These were more pronounced in MDR than in WT cells. Increasing the incubation temperature from 37 to 42 degrees Celsius enhances cytotoxicity in cells exposed to spermine metabolites. The combination BSAO/spermine prevents tumor growth, particularly well if the enzyme has been conjugated to a biocompatible hydrogel polymers. Since both wild-type and MDR cancer cells after pre-treatment with MDL 72527, a lysosomotropic compound, are sensitized to subsequent exposure to BSAO/spermine, it is conceivable that combined treatment with a lysosomotropic compound and BSAO/spermine would be effective against tumor cells. It is of interest to search for such novel compounds, which might be promising for application in a therapeutic setting.
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