Selective G protein coupling by C-C chemokine receptors

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• C-C chemokines are key in monocyte and T cell chemotaxis during inflammation.
• Understanding chemokine receptor signaling pathways is crucial for inflammatory disease research.

Purpose of the Study:

• To investigate the specific pathways by which C-C chemokine receptors activate phospholipase C (PLC).
• To determine the G protein coupling specificity of C-C chemokine receptors (CKR-1, MCP-1Ra, MCP-1Rb).

Main Methods:

• Cotransfection of COS-7 cells with C-C chemokine receptors and G protein alpha subunits.
• Measurement of ligand-induced inositol phosphate accumulation.
• Pertussis toxin sensitivity assays to assess Gi protein involvement.

Main Results:

• CKR-1, MCP-1Ra, and MCP-1Rb reconstituted PLC beta2 activation via Gi proteins.
• Receptors showed differential coupling specificity to Gq class alpha subunits (Galphaq/11, Galpha14, Galpha16).
• MCP-1Rb coupled to Galpha14 and Galpha16, while its variant and CKR-1 showed distinct couplings, highlighting C-terminal domain importance.

Conclusions:

• C-C chemokine receptor C-terminal domains dictate specific G protein coupling.
• Differential Gq protein coupling suggests distinct in vivo functions for chemokines.
• The conserved Gi-Gbetagamma-PLC beta2 pathway presents a target for broad-spectrum anti-inflammatory therapies.