Clusterin, also known as Apolipoprotein J (ApoJ), is a ubiquitous multifunctional glycoprotein that can interact with a broad spectrum of molecules such as complement components, various receptors, and the Alzheimer’s b-amyloid peptide. Clusterin expression is increased in Alzheimer’s disease brain tissue and clusterin-immunoreactive amyloid plaques are found associated with phospho-tau-positive dystrophic neurites and it has been suggested that clusterin facilitates the conversion of diffuse b-amyloid deposits into amyloid and enhances tau phosphorylation in neurites around these plaques. Other reports show that clusterin expression is decreased in proliferating cells and is upregulated in quiescent and senescent cells, suggesting that it may also play a role in aging and tumorigenesis suppression. Clusterin exists in at least two distinct isoforms.