Constrained Peptides as Small Antagonists of the Chemokine Receptor CXCR4 - PEPSAR
Coordinating Institution:
CRP Sante
Other Partner(s):
Institut Gilbert Laustriat, Strasbourg (F)
From: 01/09/2007
To: 31/08/2009
Budget: 297,497.00€
Contact(s):
Deroo Sabrina
Summary
The chemokine receptor CXCR4 is one of the principal coreceptors used by the Human Immunodeficiency Virus type 1 (HIV-1) to infect lymphocytes. The CXCR4-CXCL12 interaction plays also a key role in cancer cell metastasis, leukemia and rheumatoid arthritis. In this regard, the development of molecules binding to CXCR4 without activating the receptor (antagonists) holds promising therapeutic applications. Indeed, these antagonists could inhibit the interaction of the receptor CXCR4 with HIV-1 and lead to a reduction of the viral load in HIV patients decreasing the HIV-1 morbidity. By inhibiting the CXCR4-CXCL12 interaction, reduction of cancer metastasis could be achieved.
More than 90% of the cancer-related deaths are due to metastatic processes. Reducing these processes could have a great impact on cancer treatments and cancer mortality. To date, there is a considerable need to identify new potent and selective CXCR4 inhibitors. The objectives of the current research proposal were (I) to identify new structurally constrained peptide CXCR4 ligands on a simplified model of CXCR4 developed at the Laboratory of Retrovirology and (II) to characterize their interaction in terms of agonists or antagonists in binding and functional assays. The simplified CXCR4 model was used as target to identify new ligands by screening phage libraries displaying fully randomized peptides. In total, 25 screening campaigns were performed with 7 different phage displayed peptide libraries.
The selection campaigns resulted in the isolation of 7 phage clones binding to the simplified model. However, these phage clones were not exclusively binding to the model and interacted also with irrelevant targets. Peptides displayed by these phage libraries were too flexible and were not able to adopt a structure allowing specific binding to CXCR4 model. A new strategy was developed using a complete chemokine protein as a scaffold to reduce the structural flexibility. A novel phage library was engineered displaying mutated chemokine proteins. Screening campaigns on the simplified model with the new library resulted in the isolation of 19 chemokine mutants. Preliminary data on the characterization of these mutants suggested that 5 chemokine mutants acted as antagonists in 2 different functional assays.
These data confirm the use of our simplified CXCR4 model as target and underline the value of our new phage library displaying chemokine mutants to identify new CXCR4 antagonists. Further characterization of these ligands is required to confirm their antagonist activity and evaluate their potential therapeutic use in the field of HIV-1 and cancer.