Wnt signalling is known to require the presence of heparan sulfate proteoglycans (HSPGs). Sulf1, an enzyme that acts to modifiy the structure of HSPGs, has been shown to promote canonical Wnt signalling in tissue culture cells. We have preliminary data that indicates the effects of Sulf1 on Wnt signalling are complex. Our hypothesis is that Sulf1 activity modulates cellular response to Wnt signalling through canonical and non-canonical pathways. To investigate this, we will analyse the molecular mechanism that underlies the impact of XtSulf1 on Wnt signalling as well as its functional relevance in vivo. Our specific aims are to:
1. Determine the ability of the Wnt co-receptors (LRP5/6, Frizzled3/7, and Ror2) to associate with different Wnt ligands, and establish the effects of Sulf1 activity on the formation of these signalling complexes.
2. Determine the relevance of endocytosis of Wnt receptor complexes into different vesicle trafficking pathways, and establish the effects of Sulf1 on the internalisation of signalling complexes using con-focal microscopy and live-cell imaging.
3. Determine the biological activity of Sulf1 by analysing out put from the canonical and non-canonical Wnt signalling pathways in embryos and explants over expressing XtSulf1.
4. Determine the endogenous requirement for XtSulf1 in modulating Wnt signalling during development by examining the activity of canonical and non-canonical Wnt pathways in X.tropicalis embryos lacking XtSulf1.
Cells in all animals are surrounded by a sticky matrix that holds them together and helps in relaying messages from one cell to another. We have found that when this matrix is modified messages can no longer be received by a cell or, on the other hand, sometimes messages are received more efficiently. We are working on a gene called XtSulf1 that makes an enzyme that re-structures the matrix on cells. We want to know whether this enzyme will change the ability of a cell to respond to a message called Wnt. We will investigate exactly what underlies the effects of XtSulf1 on Wnt. All the players involved in these processes are important and we want to determine what is happening at the level of the cell and the messages. The Wnt message is known to be important for embryos to develop properly, for stem cells to grow in culture and is also known to be mis-regulated in disease: therefore a good understanding of how this message can be controlled will be important in developing new medical therapies and for the advancement of regenerative medicine.
This project demonstrated that XtSulf1 enhances noncanonical Wnt signalling in Xenopus. In contrast, we found that XtSulf1 inhibits the induction of a second organiser by Wnt8, however this same effect is not evident when all canonical Wnt ligands are assayed in the same way. We have found that Sulf1 has distinct effects on Wnt8, Wnt3a and Wnt1 using biological assays and immunoprecipitation. We have also determined the impact of Sulf1 on both Wnt and Hh ligands.
|Acronym||Sulf1 regulation of Wnt signalling|
|Effective start/end date||26/04/10 → 30/09/13|