Complement-mediated neurotoxicity is regulated by homologous restriction

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Beta-amyloid peptides activate the complement cascade, and complement proteins like the membrane attack complex (C5b-9) are found in Alzheimer's disease brains.
• This suggests a potential role for the complement system in neurodegenerative disorders.

Purpose of the Study:

• To investigate the effect of complement activation on neuronal cell death.
• To determine the role of homologous restriction in protecting neurons from complement-mediated lysis.

Main Methods:

• Studied complement activation and cell death in nerve growth factor (NGF)-differentiated PC12 cells and retinoic acid (RA)-differentiated SH-SY5Y cells treated with human serum.
• Assessed the presence of CD59 on SH-SY5Y cells using PCR and immunocytochemistry.
• Investigated the effect of phosphatidylinositol-specific phospholipase C (PI-PLC) on SH-SY5Y cell vulnerability to complement.

Main Results:

• Human serum activated complement (iC3b formation) in both PC12 and SH-SY5Y cells, but only PC12 cells underwent lysis.
• SH-SY5Y cells expressed CD59, a glycosylphosphatidylinositol (GPI)-anchored protein that inhibits membrane attack complex formation, conferring resistance to complement.
• Treatment with PI-PLC removed GPI-anchored proteins, rendering SH-SY5Y cells susceptible to complement-mediated cell death; reconstituted C5b-9 was toxic to both cell types.

Conclusions:

• Complement activation can induce neuronal cell death.
• The protein CD59 plays a crucial role in protecting human neuronal cell lines from complement-mediated lysis through homologous restriction.
• These findings highlight the complex interplay between the complement system and neuronal survival in neurodegenerative contexts.