Chapter 7: Cell protective functions of secretory Clusterin (sCLU).

Secretory clusterin (sCLU) is found as an 80-kDa glycoprotein in virtually all body fluids, in serum it is associated with high-density lipoprotein (HDL). Here, we discuss demonstrated and proposed mechanisms of the cytoprotective functions of sCLU in instances of apoptosis, necrosis, and disease. These include prevention from cell damage by lipid oxidation in blood vessels, removal of dead cell remnants in tissues undergoing various forms of cell death, and clearance of harmful extracellular molecules such as amyloid beta (Abeta) by endocytosis or transcytosis. All these functions may reflect the propensity of sCLU to bind to a wide spectrum of hydrophobic molecules on one hand and to specific cell-surface receptors on the other hand. Identified and proposed sCLU receptors are members of the LDL receptor family of endocytosis receptors. Since these receptors recently have proved to modulate cell signaling we will discuss whether sCLU due to this interaction not only targets its ligands for clearance, but may also be involved in triggering signal transduction.