cartilage intermediate layer protein 1 (CILP-1, CILP)
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Function
- cartilage scaffolding
- antagonizes TGFB1 & IGF1 (putative)
- suppresses IGF1-induced proliferation & sulfated proteoglycan synthesis
- inhibits ligand-induced IGF1R autophosphorylation
- interacts with TGFB1
- cleaved into 2 chains by a furin-like protease upon or preceding secretion (putative)
Structure
- contains 1 Ig-like C2-type domain (immunoglobulin-like domain)
- contains 1 TSP type-1 domain
Compartment
secreted, extracellular matrix
Expression
- specifically expressed in cartilage
- localizes in the intermediate layer of articular cartilage but neither in the superficial nor in the deepest regions
- specifically expressed in intervertebral disk tissue
- expression increases with aging in hip articular cartilage.
Pathology
- overexpression may lead to impair chondrocyte growth & matrix repair & indirectly promote inorganic pyrophosphate supersaturation in aging & osteoarthritis cartilage
- overexpressed in articular hyaline cartilage from patients with calcium pyrophosphate dihydrate crystal deposition disease (CPPD)
- defects in CILP may be a cause of susceptibility to lumbar disk disease
- antibodies against CILP are detected in patients with early-stage knee osteoarthritis (OA) & rheumatoid arthritis
- autoantibodies against the C1 & C2 chains are detected in 10/136 (C1) & 17/136 (C2) patients with OA