The discoidin domain receptors: collagen binding specificity and cooperation with integrins in cell adhesion / migration
Lead Research Organisation:
Imperial College London
Department Name: National Heart and Lung Institute
Abstract
We aim to study how cells use specialised proteins, called DDRs, to interact with collagen. When DDRs are faulty, they can cause disease. It is hoped that our work will benefit human health by creating reagents that may be useful in anti-DDR drug discovery programmes.
The DDRs are novel drug targets for a number of human diseases, including arthritis and certain cancers. The DDRs recognise collagen, but we know very little about this interaction. When the DDRs bind collagen, they transmit a signal into the cell. We do not understand how the DDRs transmit such information.
Collagen is the most abundant protein in our body and has a very complex structure. It is built like a rope, composed of three very long strands of amino acids that wind around each other. We will characterise the parts of collagen that are recognised by the DDRs. We will produce synthetic collagen fragments with the same rope-like structure as collagen and test which of these the DDRs use to transmit signals into cells.
The DDRs are not the only proteins that interact with collagen. Another type of protein called integrin also binds collagen. Because the DDRs and integrins both recognise collagen, their relative contribution to biological function has been difficult to study. We have recently discovered that DDRs recognise a different part of collagen than integrins. We can thus make synthetic collagen fragments that will bind only DDRs, but not integrins, and use these to understand how the DDRs regulate the cell’s function.
The DDRs are novel drug targets for a number of human diseases, including arthritis and certain cancers. The DDRs recognise collagen, but we know very little about this interaction. When the DDRs bind collagen, they transmit a signal into the cell. We do not understand how the DDRs transmit such information.
Collagen is the most abundant protein in our body and has a very complex structure. It is built like a rope, composed of three very long strands of amino acids that wind around each other. We will characterise the parts of collagen that are recognised by the DDRs. We will produce synthetic collagen fragments with the same rope-like structure as collagen and test which of these the DDRs use to transmit signals into cells.
The DDRs are not the only proteins that interact with collagen. Another type of protein called integrin also binds collagen. Because the DDRs and integrins both recognise collagen, their relative contribution to biological function has been difficult to study. We have recently discovered that DDRs recognise a different part of collagen than integrins. We can thus make synthetic collagen fragments that will bind only DDRs, but not integrins, and use these to understand how the DDRs regulate the cell’s function.
Technical Summary
The human discoidin domain receptors, DDR1 and DDR2, are highly unusual receptor tyrosine kinases that are activated by a major constituent of the extracellular matrix, collagen. Next to the collagen-binding integrins, the DDRs are the most widely distributed collagen receptors in mammals. The DDRs are important in development and aberrant DDR function leads to human disease. In particular, DDRs are responsible for disease progression in fibrotic diseases, arthritis and several types of cancer. In contrast to the situation with integrins, not much is known about the DDR-collagen interaction. Both DDRs are activated by a number of different collagen types, and activation is strictly dependent on the native, triple-helical conformation of collagen.
Our previous work has shown that the DDRs bind collagen with high affinity and in a highly specific manner. Very recently, using synthetic triple-helical peptides derived from collagen, we identified a specific sequence in collagen II recognised by DDR2 (unpublished results). This amino acid motif is distinct from that recognised by integrins and the platelet collagen receptor GPVI. Importantly, triple-helical peptides comprising the DDR2 binding site not only inhibit DDR2 binding to collagen II, but activate DDR2 autophosphorylation in a specific manner. Thus, we are now in a unique position to use high-affinity DDR2-specific collagen peptides as a research tool to investigate the cellular function of DDR2.
The aims of this proposal are twofold: 1) to define DDR1 and DDR2 binding sites in other collagens, and 2) to use our DDR-selective ligands to probe the contribution of the DDRs to cell adhesion and migration. Although the two DDRs are homologous, their collagen binding specificities are distinct; our studies will establish the molecular basis for these differences. The DDRs play important roles in cell adhesion and migration, but integrins are thought to be the primary mediators of these processes. The fact that both types of receptor recognise the same ligand (collagen) has complicated the analysis of their relative contributions. Using our new DDR-specific peptides, together with previously developed integrin-specific peptides, we are now able to discriminate between integrin-initiated and DDR-initiated events in cell adhesion and migration. We will study the possible cooperation between the DDRs and integrins. The results obtained from this research programme will establish the collagen binding specificities of the DDRs and give important novel insight into the roles of the DDRs in cell adhesion and migration.
Our previous work has shown that the DDRs bind collagen with high affinity and in a highly specific manner. Very recently, using synthetic triple-helical peptides derived from collagen, we identified a specific sequence in collagen II recognised by DDR2 (unpublished results). This amino acid motif is distinct from that recognised by integrins and the platelet collagen receptor GPVI. Importantly, triple-helical peptides comprising the DDR2 binding site not only inhibit DDR2 binding to collagen II, but activate DDR2 autophosphorylation in a specific manner. Thus, we are now in a unique position to use high-affinity DDR2-specific collagen peptides as a research tool to investigate the cellular function of DDR2.
The aims of this proposal are twofold: 1) to define DDR1 and DDR2 binding sites in other collagens, and 2) to use our DDR-selective ligands to probe the contribution of the DDRs to cell adhesion and migration. Although the two DDRs are homologous, their collagen binding specificities are distinct; our studies will establish the molecular basis for these differences. The DDRs play important roles in cell adhesion and migration, but integrins are thought to be the primary mediators of these processes. The fact that both types of receptor recognise the same ligand (collagen) has complicated the analysis of their relative contributions. Using our new DDR-specific peptides, together with previously developed integrin-specific peptides, we are now able to discriminate between integrin-initiated and DDR-initiated events in cell adhesion and migration. We will study the possible cooperation between the DDRs and integrins. The results obtained from this research programme will establish the collagen binding specificities of the DDRs and give important novel insight into the roles of the DDRs in cell adhesion and migration.
