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Identification of allosteric peptide agonists of CXCR4
Aristidis Sachpatzidis1, Benjamin K Benton, John P Manfredi
1Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Abstract:
The chemokine receptor CXCR4 is a co-receptor for T-tropic strains of HIV-1. A number of small molecule antagonists of CXCR4 are in development but all are likely to lead to adverse effects due to the physiological function of CXCR4. To prevent these complications, allosteric agonists may be therapeutically useful as adjuvant therapy in combination with small molecule antagonists. A synthetic cDNA library coding for 160,000 different SDF-based peptides was screened for CXCR4 agonist activity in a yeast strain expressing a functional receptor. Peptides that activated CXCR4 in an autocrine manner induced colony formation. Two peptides, designated RSVM and ASLW, were identified as novel agonists that are insensitive to the CXCR4 antagonist AMD3100. In chemotaxis assays using the acute lymphoblastic leukemia cell line CCRF-CEM, RSVM behaves as a partial agonist and ASLW as a superagonist. The superagonist activity of ASLW may be related to its inability to induce receptor internalization. In CCRF-CEM cells, the two peptides are also not inhibited by another CXCR4 antagonist, T140, or the neutralizing monoclonal antibodies 12G5 and 44717.111. These results suggest that alternative agonist-binding sites are present on CXCR4 that could be screened to develop molecules for therapeutic use.
Insights
Novel CXCR4 agonists, RSVM and ASLW, were discovered. These peptides show therapeutic potential as adjuvant therapy for HIV-1, offering a new approach to managing CXCR4-related complications.
Area of Science:
- Immunology
- Virology
- Drug Discovery
Background:
- CXCR4 is a co-receptor for T-tropic HIV-1 strains.
- Existing CXCR4 antagonists may cause adverse effects due to CXCR4's physiological roles.
- Allosteric agonists are explored as potential adjuvant therapies with antagonists.
Purpose of the Study:
- To identify novel CXCR4 agonists.
- To investigate the therapeutic potential of these agonists in combination with antagonists.
- To explore alternative binding sites on CXCR4 for drug development.
Main Methods:
- Screening of a synthetic cDNA library for CXCR4 agonist activity in yeast.
- Autocrine activation and colony formation assays.
- Chemotaxis assays using CCRF-CEM cells and CXCR4 antagonists (AMD3100, T140) and antibodies (12G5, 44717.111).
Main Results:
- Two novel CXCR4 agonists, RSVM (partial agonist) and ASLW (superagonist), were identified.
- RSVM and ASLW are insensitive to the CXCR4 antagonist AMD3100.
- ASLW's superagonist activity may stem from its lack of receptor internalization.
- These peptides are also resistant to inhibition by T140, 12G5, and 44717.111.
Conclusions:
- Novel allosteric binding sites on CXCR4 may exist.
- RSVM and ASLW represent promising candidates for developing new therapeutic strategies against HIV-1.
- These findings support the development of CXCR4 agonists as adjuvant therapy.