Determination of Versikine Levels by Enzyme-Linked Immunosorbent Assay (ELISA).

The proteoglycan versican plays multiple roles in cancer progression, from promoting cell invasion and proliferation to evasion of immune surveillance. Metalloproteinases of the A Disintegrin and Metalloproteinase with Thrombospondin-like motif (ADAMTS) family cleave versican at a specific Glu-Ala bond, thus releasing a bioactive fragment named versikine, whose biological function, still not entirely revealed, seems that of antagonizing the effects of the parental molecule. Here we describe an enzyme-linked immunosorbent assay (ELISA) that specifically detects versikine in media, pure component systems, and biological fluids using neoepitope antibodies. Such antibodies recognize their target proteolytic fragment but not the intact, parental molecule. Versikine fragments are captured by neoepitope antibodies and detected by antibodies directed against its N-terminal globular (G1) domain. The method here described can therefore be used to measure ADAMTS versicanase activity and provides a quantitative alternative to immunoblotting.

Expression and Purification of Recombinant ADAMTS8.

ADAMTS8 (A Disintegrin-like and Metalloproteinase with Thrombospondin motifs 8) is a secreted zinc-dependent metalloproteinase whose expression is downregulated in a variety of solid tumors. Xenografts expressing high levels of ADAMTS8 have a poor capacity to invade and migrate in nude mice. While this data highlights a beneficial, anti-cancerogenic role of ADAMTS8, the mechanism behind this activity is still not fully elucidated. So far, the only reported substrate for ADAMTS8 is osteopontin (OPN), an extracellular matrix protein widely implicated in multiple steps of cancer progression, albeit, similar to other ADAMTS family members, it is very likely that ADAMTS8 cleaves a variety of substrates. The availability of purified ADAMTS8 may enlighten the biological role of this metalloproteinase.Here we describe methods for expression and purification of recombinant ADAMTS8 in HEK293T cells as well as a convenient assay to test ADAMTS8 proteolytic activity using OPN as a substrate.

The C-terminal domains of ADAMTS1 contain exosites involved in its proteoglycanase activity.

A disintegrin-like and metalloproteinase with thrombospondin type 1 motifs (ADAMTS1) is a protease involved in fertilization, cancer, cardiovascular development, and thoracic aneurysms. Proteoglycans such as versican and aggrecan have been identified as ADAMTS1 substrates, and Adamts1 ablation in mice typically results in versican accumulation; however, previous qualitative studies have suggested that ADAMTS1 proteoglycanase activity is weaker than that of other family members such as ADAMTS4 and ADAMTS5. Here, we investigated the functional determinants of ADAMTS1 proteoglycanase activity. We found that ADAMTS1 versicanase activity is approximately 1000-fold lower than ADAMTS5 and 50-fold lower than ADAMTS4 with a kinetic constant (kcat/Km) of 3.6 × 103 M-1 s-1 against full-length versican. Studies on domain-deletion variants identified the spacer and cysteine-rich domains as major determinants of ADAMTS1 versicanase activity. Additionally, we confirmed that these C-terminal domains are involved in the proteolysis of aggrecan as well as biglycan, a small leucine-rich proteoglycan. Glutamine scanning mutagenesis of exposed positively charged residues on the spacer domain loops and loop substitution with ADAMTS4 identified clusters of substrate-binding residues (exosites) in ß3-ß4 (R756Q/R759Q/R762Q), ß9-ß10 (residues 828-835), and ß6-ß7 (K795Q) loops. This study provides a mechanistic foundation for understanding the interactions between ADAMTS1 and its proteoglycan substrates and paves the way for development of selective exosite modulators of ADAMTS1 proteoglycanase activity.