Competitive inhibition of the classical complement pathway using exogenous single-chain C1q recognition proteins

Area of Science:

• Neuroimmunology
• Innate Immunity
• Molecular Biology

Background:

• Complement component C1q is crucial in innate immunity and the classical complement pathway.
• C1q plays a role in synapse elimination in both healthy and diseased brains, but its mechanism is unclear.

Purpose of the Study:

• To design and validate novel protein constructs (sc-gC1q) that inhibit C1q function.
• To investigate the potential of sc-gC1q proteins for studying C1q's role in the central nervous system.

Main Methods:

• Engineered single-chain globular C1q (sc-gC1q) constructs lacking the collagen-like region.
• Utilized mass spectrometry, SEC, AUC, CD spectroscopy, ELISA, and SPR for structural and functional validation.
• Assessed binding interactions with complement activators, immunoglobulins, and neuronal pentraxins.

Main Results:

• Validated the structure and binding capabilities of sc-gC1q proteins.
• Demonstrated potent inhibition of C1q function by sc-gC1qs.
• Showed that sc-gC1qs compete with C1q for binding to embryonal neuronal cell membranes.

Conclusions:

• sc-gC1q proteins effectively inhibit C1q function and can be used to study C1q's neuronal localization and roles.
• These engineered molecules offer a basis for developing therapeutic inhibitors targeting C1q in neurological conditions.