Nerve growth factor: activation of the classical complement pathway by specific substitution for component C1-

Area of Science:

• Immunology
• Neuroscience
• Biochemistry

Background:

• Nerve growth factor (NGF) plays a crucial role in neuronal development and survival.
• The classical complement pathway is a key part of the innate immune system, involving a cascade of protein activations.
• Previous studies have noted NGF's ability to accelerate wound healing, but the underlying mechanisms remain incompletely understood.

Purpose of the Study:

• To investigate the interaction between purified mouse submandibular gland nerve growth factor (NGF) and the classical complement pathway.
• To determine if NGF possesses enzymatic activities associated with complement components.
• To explore the potential role of this interaction in NGF's known biological effects, such as wound contraction.

Main Methods:

• Homogeneous preparations of mouse submandibular gland NGF were utilized.
• Enzyme assays were performed to assess NGF's ability to cleave complement zymogens C4 and C2.
• The effect of human C1- inactivator on NGF's complement-associated activity was examined.

Main Results:

• NGF demonstrated enzyme activities characteristic of the first component (C1-) of the classical complement pathway.
• Specifically, NGF was capable of cleaving the zymogen forms of C4 and C2.
• NGF did not substitute for other classical pathway components (C2-C9).
• The C1(-)-like activity of NGF was found to be inhibited by human C1- inactivator.

Conclusions:

• Nerve growth factor (NGF) exhibits C1(-)-like enzymatic activity within the classical complement pathway.
• This interaction involves the cleavage of C4 and C2, mimicking the function of C1-.
• The observed interaction between NGF and the complement system provides a potential explanation for NGF's role in accelerating wound contraction.