CHI3L1 (Chitinase 3-like Protein 1), also known as YKL-40, is a secreted glycoprotein belonging to the chitinase-like protein family. Despite lacking chitinase enzymatic activity, CHI3L1 plays important roles in neuroinflammation, astrogliosis, and microglial activation. It serves as both a biomarker for neuroinflammatory conditions and a potential therapeutic target in neurodegenerative diseases.
The CHI3L1 gene is located on chromosome 1q32.1 and encodes a 383-amino acid secreted protein with a molecular weight of approximately 40 kDa. The protein contains:
Unlike true chitinases, CHI3L1 lacks the catalytic glutamate residue in its active site and cannot hydrolyze chitin.
CHI3L1 is primarily expressed in:
In Alzheimer's disease, elevated CHI3L1 levels in cerebrospinal fluid (CSF) and brain tissue correlate with:
CHI3L1 is thought to promote neuroinflammation through:
Elevated CHI3L1 expression has been observed in:
The protein may contribute to:
CHI3L1 is being investigated as a:
Approaches targeting CHI3L1 include:
CHI3L1 interacts with several signaling pathways:
CHI3L1 → [AKT signaling](/proteins/akt-protein) → Cell survival
CHI3L1 → [ERK1/2 signaling](/proteins/mapk1-protein) → Proliferation
CHI3L1 → [NF-κB](/entities/nf-kappa-b) → Inflammation
CHI3L1 → [PI3K/AKT](/proteins/akt-protein) → Anti-apoptotic effects