• Purity

  >95%, by SDS-PAGE under reducing conditions and visualized by silver stain

• Endotoxin Level

  <0.01 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its ability to induce adhesion of ATDC5 mouse chondrogenic cells.

  The ED₅₀ for this effect is 0.5-2.0 μg/mL.

  Optimal dilutions should be determined by each laboratory for each application. Also measured by its ability to bind Recombinant Human TGF‑ beta 1 (Catalog # 240-B).

• Source

  Mouse myeloma cell line, NS0-derived Met1-Arg720, with a C-terminal 6-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Arg22

• Predicted Molecular Mass

  78.8 kDa

• SDS-PAGE

  85-95 kDa, reducing conditions

Background: CILP-1

CILP‑1 (cartilage intermediate‑layer protein 1; CILP C1) is a 92 kDa secreted monomeric cartilage glycoprotein that is the N‑terminal portion of a proteolytically cleaved 138 kD precursor (1, 2). The 62 kDa C‑terminal fragment, called CILP C2, is also secreted; while thought to resemble a nucleoside triphosphate pyrophosphohydrolase (NTPPHase), it has no enzyme activity (2 ‑ 4). Mature human CILP‑1 (aa 22 ‑ 720) contains a TSP‑1 domain (aa 149 ‑ 201) and a C2‑type Ig‑like region (aa 309 ‑ 395) and shares 89% and 42% aa sequence identity with mouse CILP‑1 and human CILP‑2, respectively. CILP‑1 is produced by chondrocytes in both hyaline and fibrocartilage, and preferentially found in the inter‑territorial matrix of the interior layers of articular cartilage (1, 2). Its expression increases with age and correlates with osteoarthritis (1, 2, 5 ‑ 7). While CILP‑1 expression is induced by TGF‑ beta 1‑activated SMAD3, the secreted protein binds and inhibits TGF‑ beta 1 activities, such as induction of cartilage matrix genes (4 ‑ 6, 8). A polymorphism producing the aa substitution I395T enhances inhibition of TGF‑ beta 1 and is significantly associated with lumbar disc disease in Japanese populations, but not in Finnish or Chinese populations (4, 9). Additionally, chondrocyte CILP‑1 expression is inhibited by IGF‑1   in vitro, but CILP‑1 protein blocks IGF‑1 activities such as proliferation and down‑regulation of extracellular inorganic pyrophosphate (ePPi) production (3, 5, 6). In a model of aged cartilage where TGF‑ beta 1 is dominant, increased CILP‑1 inhibits both IGF‑1 and TGF‑ beta 1 activities, slowing cartilage repair due to reduced chondrocyte proliferation and matrix production. At the same time, increased production of ePPi promotes crystals that are a factor in osteoarthritis (3).

• References:

1. Lorenzo, P. et al. (1998) J. Biol. Chem. 273:23469.

2. Lorenzo, P. et al. (1998) J. Biol. Chem. 273:23463.

3. Johnson, K. et al. (2003) Arthritis Rheum. 48:1302.

4. Seki, S. et al. (2005) Nat. Genet. 37:607.

5. Hirose, J. et al. (2002) Arthritis Rheum. 46:3218.

6. Hirose, J. et al. (2000) Arthritis Rheum. 43:2703.

7. Lorenzo, P. et al. (2004) Matrix Biol. 23:381.

8. Mori, M. et al. (2006) Biochem. Biophys. Res. Commun. 341:121.

9. Virtanen, I.M. et al. (2007) J. Med. Genet. 44:285.

• Long Name:

  Cartilage Intermediate Layer Protein 1

• Entrez Gene IDs:

  8483 (Human); 214425 (Mouse); 315761 (Rat)

• Alternate Names:

  cartilage intermediate layer protein 1 C1; cartilage intermediate layer protein 1 C2; cartilage intermediate layer protein 1; cartilage intermediate layer protein, nucleotide pyrophosphohydrolase; Cartilage intermediate-layer protein; CILP; CILP1; CILP-1; HsT18872