Cartilage intermediate layer protein 1 (CILP1)

Cartilage intermediate layer protein 1 (CILP1) is a large glycoprotein encoded by the CILP gene, predominantly localized in the intermediate zone of articular cartilage and the nucleus pulposus of intervertebral discs[1][3][6][8]. Structurally, CILP1 contains a von Willebrand factor type A domain, thrombospondin type 1 repeat, and a C-terminal globular domain[1][6]. Functionally, it provides structural support to cartilage and plays a central role in regulating the extracellular matrix, influencing collagen and proteoglycan synthesis and matrix assembly[1][8]. CILP1 acts as an antagonist to TGF-β and IGF-1, inhibiting their signaling activities and suppressing chondrocyte proliferation and repair processes, which leads to its implication in degenerative conditions such as osteoarthritis and intervertebral disc disease[3][4][5][6][8][10]. Genetically, CILP1 variants are associated with risk of lumbar disc disease[3][4][8]. In the heart, CILP1 is emerging as a mediator of cardiac fibrosis by interfering with pro-fibrotic TGF-β signaling[10]. No drugs currently target CILP1 directly, but its modulation of key signaling pathways makes it a potential biomarker and therapeutic candidate in degenerative and fibrotic diseases.

Other names

Cartilage intermediate-layer proteinCILPCartilage intermediate layer protein 1 C1Cartilage intermediate layer protein 1 C2CILP-1HsT18872UNQ602/PRO1188nucleotide pyrophosphohydrolase (historically, but now considered inaccurate)

Proposed: Antagonism of transforming growth factor-β (TGF-β) signaling by binding and inhibiting TGF-β receptor interactions; Proposed: Antagonism of insulin-like growth factor-1 (IGF-1) signaling by suppressing chondrocyte proliferation and matrix synthesis