|Detection of Human Clusterin beta chain by Western Blot. Western blot shows lysates of human liver tissue and human serum. PVDF membrane was probed with 1 µg/mL of Sheep Anti-Human Clusterin aa 22-227 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7084) followed by HRP-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # HAF016). Specific bands were detected for Clusterin Precursor at approximately 60-65 kDa and Clusterin beta chain at approximately 36 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.|
|Clusterin in Human Brain. Clusterin was detected in immersion fixed paraffin-embedded sections of human Alzheimer's brain using Sheep Anti-Human Clusterin aa 22-227 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7084) at 1.7 µg/mL overnight at 4 °C. Tissue was stained using the Anti-Sheep HRP-DAB Cell & Tissue Staining Kit (brown; Catalog # CTS019) and counterstained with hematoxylin (blue). Specific staining was localized to neuronal cell bodies and processes. View our protocol for Chromogenic IHC Staining of Paraffin-embedded Tissue Sections.|
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, and 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 80 kDa N-glycosylated disulfide-linked heterodimer (7, 8). Mature human Clusterin shares 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 (9, 10). In human, an alternately spliced 50 kDa isoform of Clusterin (nCLU) lacks the signal peptide and remains intracellular (5, 11). This molecule is neither glycosylated nor cleaved into alpha and beta chains (11). In the cytoplasm, nCLU destabilizes the actin cytoskeleton and inhibits NF kappa B activation (12, 13). Cellular exposure to ionizing radiation promotes the translocation of nCLU to the nucleus where it interacts with Ku70 and promotes apoptosis (5, 11). This function contrasts with the cytoprotective effect of secreted Clusterin (14). During colon cancer tumor progression there is a downregulation of the intracellular form and an upregulation of the glycosylated secreted form (11).