Human Clusterin Quantikine ELISA Kit Summary

Product Summary

The Quantikine Human Clusterin Immunoassay is a 4.5 hour solid-phase ELISA designed to measure human Clusterin in cell culture supernates, serum, plasma, urine, and saliva. It contains NS0-expressed recombinant human Clusterin and has been shown to accurately quantitate the recombinant factor. Results obtained using natural human Clusterin showed linear curves that were parallel to the standard curves obtained using the Quantikine kit standards. These results indicate that this kit can be used to determine relative mass values for naturally occurring human Clusterin.

Preparation and Storage

Background: Clusterin

Clusterin [also known as Apolipoprotein J, Sulfated Glycoprotein 2 (SGP-2), TRPM-2, and SP-40], is a secreted multifunctional protein that was named for its ability to induce cellular clustering. It binds a wide range of molecules and may function as a chaperone of misfolded extracellular proteins. It also participates in the control of cell proliferation, apoptosis, and carcinogenesis (1, 2). Clusterin is predominantly expressed in adult testis, ovary, adrenal gland, liver, heart, brain, and in many epithelial tissues during embryonic development (3). Human Clusterin is synthesized as a precursor that contains two coiled coil domains, three nuclear localization signals (NLS), and one heparin binding domain (4 - 6). Intracellular cleavages of the precursor remove the signal peptide and generate comparably sized alpha and beta chains which are secreted as an approximately 80 kDa N-glycosylated and disulfide-linked heterodimer (7-9). Mature human Clusterin shares a 77% amino acid sequence identity with mouse and rat Clusterin. 

High μg/mL concentrations of Clusterin circulate predominantly as a component of high density lipoprotein particles, and these are internalized and degraded through interactions with LRP-2/Megalin (10, 11). The ability of Clusterin to bind and neutralize non-oxidatively modified LDL reduces cytotoxicity in atherosclerotic plaques (12). The chaperone function of Clusterin helps to reduce the accumulation of beta -amyloid fibrils and damage due to amyloid plaques in Alzheimer's disease (13). An alternately spliced 50 kDa isoform of human Clusterin (nCLU) remains intracellular and is neither glycosylated nor cleaved into alpha and beta chains (5, 14). Cellular exposure to ionizing radiation promotes the translocation of nCLU to the nucleus where it interacts with Ku70 and promotes apoptosis (5, 14). This function contrasts with the cytoprotective effect of secreted Clusterin (15). During tumor progression, nCLU is down regulated while the secreted form is upregulated and may be aberrantly glycosylated (14, 16, 17). Increased circulating levels of Clusterin enhance tumor aggressiveness by inhibiting apoptosis and by promoting the epithelial to mesenchymal transition (18-20).

Assay Procedure

Refer to the product datasheet for the complete assay procedure.

Bring all reagents and samples to room temperature before use. It is recommended that all samples, standards, and controls be assayed in duplicate.

1、Prepare all reagents, standard dilutions, and samples as directed in the product insert.

2、Remove excess microplate strips from the plate frame, return them to the foil pouch containing the desiccant pack, and reseal.

3、Add 50 μL of Assay Diluent to each well.

4、Add 50 μL of Standard, control, or sample to each well. Cover with a plate sealer, and incubate at room temperature for 2 hours.

5、Aspirate each well and wash, repeating the process 4 times for a total of 5 washes.

6、Add 100 μL of Conjugate to each well. Cover with a new plate sealer, and incubate at room temperature for 2 hours.

7、Aspirate and wash 5 times.

8、Add 100 μL Substrate Solution to each well.

9、Add 100 μL of Stop Solution to each well. Read at 450 nm within 30 minutes. Set wavelength correction to 540 nm or 570 nm.