Clusterin

Clusterin, also known as Apolipoprotein J (APO-J), is a protein with a molecular weight of 75-80 kDa. It exists as a disulfide-linked heterodimer and is heavily glycosylated, containing approximately 30% N-linked carbohydrates rich in sialic acid. While the predominant form is heterodimeric, truncated forms targeted to the nucleus have also been observed. The protein originates from a precursor polypeptide chain that undergoes proteolytic cleavage to remove a 22-amino acid secretory signal peptide. Subsequently, another cleavage occurs between residues 227 and 228, generating the 'a' and 'b' chains. These chains assemble in an anti-parallel orientation, forming the heterodimeric structure. Five disulfide bridges link the cysteine-rich centers of the chains. Structurally, the protein is characterized by two predicted coiled-coil alpha-helices and three predicted amphipathic alpha-helices flanking the cysteine-rich regions. Clusterin exhibits a high degree of sequence homology across various species, with similarities ranging from 70% to 80%. Its expression is nearly ubiquitous in mammalian tissues, and it can be found in various bodily fluids, including plasma, milk, urine, cerebrospinal fluid, and semen. Clusterin demonstrates the ability to bind to and form complexes with a wide array of molecules. These include immunoglobulins, lipids, heparin, bacteria, complement components, paraoxonase, beta-amyloid, leptin, and others. Consequently, clusterin has been implicated in numerous biological functions. These proposed roles include phagocyte recruitment, aggregation induction, prevention of complement attack, inhibition of apoptosis, membrane remodeling, lipid transport, hormone transport and/or scavenging, and matrix metalloproteinase inhibition. Despite extensive research, a definitive and singular function of clusterin remains elusive. However, a prevailing hypothesis suggests that clusterin acts as an extracellular chaperone, protecting cells from stress-induced damage caused by the accumulation of degraded and misfolded protein aggregates. Notably, clusterin expression levels, both at the mRNA and protein levels, are altered in various pathological and clinically relevant conditions. These include cancer, organ regeneration, infection, Alzheimer's disease, retinitis pigmentosa, myocardial infarction, renal tubular damage, and autoimmune disorders.

White powder, lyophilized, and filtered.

Human native Clusterin was sterile filtered (0.4 µm) and subsequently lyophilized from a solution of 0.5 mg/ml in 0.1 M phosphate buffer containing 0.15 M NaCl, at pH 7.5.

To prepare a working stock solution of 0.5 mg/ml, it is recommended to add deionized water to the lyophilized pellet and allow for complete dissolution. Note that the product is not sterile. Before using it for cell culture, ensure sterility by filtering the solution through an appropriate sterile filter.

Store the lyophilized Clusterin at -20°C. After reconstituting the product, aliquot it to prevent repeated freeze-thaw cycles. The reconstituted protein remains stable at 4°C for a limited period; it exhibits no significant change after storage at 4°C for two weeks.

Purity of the protein is greater than 95%, as determined by SDS-PAGE analysis.

CLI, AAG4, KUB1, SGP2, SGP-2, SP-40, TRPM2, MGC24903, Clusterin, Apolipoprotein J, Apo-J.

Plasma.