Mortalin - a multipotent chaperone regulating cellular processes ranging from viral infection to neurodegeneration.

UNLABELLED: Heat shock 70kDa protein 9 (HSPA9)/mortalin is a heat-uninducible member of the heat shock 70 protein family. This protein has been attributed many cellular functions, including energy generation, stress response, carcinogenesis and involvement in neurodegenerative diseases, which is well documented by many names it has been given (CSA, MOT, MOT2, GRP75, PBP74, GRP-75, HSPA9B, MGC4500, MTHSP75, and mortalin). As an immortalization marker (hence the name "mortalin") in mouse embryonic fibroblasts cybrids it preferentially segregated with loss of immortality in passaged cells. Mortalin regulates the functions of the tumor suppressor protein p53 and plays important roles in stress response and maintenance of the mitochondria and endoplasmic reticulum. Furthermore, mortalin appears to have roles in membrane trafficking and viral release regulation, since it interacts with Nef protein it is necessary for secretion of exosomal negative factor (Nef) and HIV-1 virus release. Recently, mortalin has been described as a significant player in neurodegenerative diseases. Mutations in HSPA9 gene have been found in Parkinson΄s disease patients; mortalin isoform expression differs in hippocampus of patients with Alzheimer΄s disease and could regulate the β-amyloid toxicity pathway. In this review we summarize the functions of mortalin, its pathological implications in neuronal dysfunction and possible roles in neurodegenerative diseases. KEYWORDS: HSPA9/mortalin/GRP75; mitochondria; cancer; Alzheimer΄s disease.