By identifying and studying novel regulators, the studies described in this thesis give substantive insights into the molecular mechanisms and different levels of control of TGF-_/BMP, IL-1_ and... Show moreBy identifying and studying novel regulators, the studies described in this thesis give substantive insights into the molecular mechanisms and different levels of control of TGF-_/BMP, IL-1_ and Wnt signaling pathways. Crucially, our work for the first time demonstrated the monoubiquitination of an I-SMAD by an E2-E3 hybrid, and added an important unraveled mechanism of how monoubiquitination could affect TGF-_/BMP signaling. We found that UBE2O participates in IL-1R/TLR4-mediated NF-_B activation via a different mechanism than in BMP signaling. Future studies of ubiquitin enzymes will benefit from our model in chapter 3, which shows that UBE2O disrupts the interaction between TRAF6 and its upstream adapter MyD88 to limit polyubiquitination of TRAF6. Our studies in this thesis also added a new DUB to the list of deubiquitinases that can regulate IL-1R/TLR4 signaling, emphasizing the importance of controlling ubiquitination status in regulating NF-_B activation. Also, we reported a new co-receptor for Wnt3a-induced signaling, suggesting compensating roles for co-receptors in the control of Wnt signaling. Therefore, the studies in this thesis yield more perception in understanding how TGF-_/BMP, IL-1R/TLR4 and Wnt signaling pathways can be regulated depending on the cell type, cell localization and cell state. Show less
Since their discovery as bone inducers, Bone Morphogenetic Proteins (BMPs) have been demonstrated to control multiple functions during embryogenesis as well as postnatally. BMPs are acting as... Show moreSince their discovery as bone inducers, Bone Morphogenetic Proteins (BMPs) have been demonstrated to control multiple functions during embryogenesis as well as postnatally. BMPs are acting as morphogenes, i.e. they can induce various cell fates at different concentrations. There are multiple regulatory mechanisms to control BMP signaling and dysregulated BMP signaling is pathologically linked with multiple diseases. This thesis presents novel studies regarding the role of elevated BMP signaling on the progression of two different genetic diseases, i.e. Fibrodysplasia Ossificans Progressiva (FOP) and Duchenne Muscular Dystrophy (DMD). Besides that, BMP signaling is tightly regulated on different levels; the activity of BMP signaling can also be modulated by other signaling pathways, such as the TGF_ and Wnt signaling pathways. In Chapter 2, we investigated the molecular mechanisms underlying TGF_ and BMP-induced conversion of endothelial cells into osteoblasts. In Chapter 3, using the BMP antagonist Noggin, we studied the role of BMP signaling in the progression of DMD disease. In Chapter 4, we described that Id3 is activated by canonical Wnt signaling in C2C12 cells, and mediates Wnt-induced myoblast proliferation and osteoblast differentiation. In Chapter 5, we showed that BMP6, in contrary to BMP7, BMP2 and BMP4, cannot be inhibited by Noggin, and identified the crucial amino acid that endows BMP6 resistance to Noggin inhibition. These findings make it possible to engineer BMPs with superior agonist activity through amino acid substitution. In Chapter 6, using exon skipping technology, we obtained an antisense oligonucleotide (AON) that specifically targets BMP type I receptor activin receptor-like kinase (ALK) 2. The ALK2 AON was shown to decrease ALK2 expression and reduced BMP6 induced osteoblast differentiation in vitro. Finally in Chapter 7, the results presented in the thesis were discussed and suggestions for future research were provided. Show less
Cai, J.; Pardali, E.; Sanchez-Duffhues, G.; Dijke, P. ten 2012
