Antagonistic peptides against human anaphylatoxin C5a

Area of Science:

• Immunology
• Biochemistry
• Molecular Biology

Background:

• The complement component 5a (C5a) is a potent anaphylatoxin involved in inflammatory and allergic responses.
• C5a exerts its effects by binding to the C5a receptor (C5aR), a G protein-coupled receptor expressed on various immune cells.

Purpose of the Study:

• To synthesize and characterize multivalent synthetic peptides derived from C5a.
• To investigate the binding affinity of these peptides to the C5a receptor (C5aR).
• To evaluate the functional effects of these peptides on C5a-mediated cellular responses, such as C5aR antagonism.

Main Methods:

• Preparation of multiple antigen peptide (MAP) constructs representing different regions of C5a.
• Binding assays using cells expressing C5aR to assess peptide affinity.
• Functional assays measuring calcium (Ca2+) mobilization and beta-hexosaminidase release in response to C5a and synthetic peptides.

Main Results:

• The C-terminal peptide MAP61-74 demonstrated high-affinity binding to cells expressing C5aR.
• N-terminal peptides (MAP3-16, MAP12-26) and a mid-portion peptide (MAP37-53) did not bind to C5aR.
• MAP61-74 inhibited C5a-induced Ca2+ mobilization and beta-hexosaminidase release, acting as a C5aR antagonist. MAP12-26 and Mono61-74 also inhibited Ca2+ mobilization.

Conclusions:

• The C-terminal region of C5a is crucial for binding to the C5a receptor (C5aR).
• The synthetic peptide MAP61-74 functions as a C5aR antagonist.
• MAP61-74 holds potential as a therapeutic agent for managing allergic responses mediated by complement activation.