CILP1 (CILP-1) inhibits ligand-induced autophosphorylation of IGF1R, the IGF-1 receptor (Johnson et al. 2003). CILP1 is expressed in chondrocytes and cultured knee meniscal cartilage cells where it blocks the ability of IGF1 to reduce extracellular pyrophosphate. Expression of CILP1 is commonly enhanced in aging and osteoarthritic cartilage.
The beta peptide of the type 1 insulin-like growth factor (IGF1R) spans the plasma membrane and trans-autophosphorylates tyrosine residues in response to binding of either IGF1 or IGF2 by the extracellular alpha peptide (LeBon et al. 1986, Yu et al. 1986, Doronio et al. 1990, Hernandez-Sanchez et al. 1995, Alvino et al. 2001).