Roles of molecular chaperones in the nervous system.

Heat shock proteins (HSPs) are induced not only by heat shock but also by various other environmental stresses. HSPs such as Hsp90, Hsp70, Hsp60, Hsp40 and Hsp28 are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from deleterious stresses. Recently, Hsc70 and Hsp40 were found to be localized to the synapse in the mammalian central nervous system, indicating a synaptic role for these HSPs. Molecular chaperones are able to inhibit the aggregation of partially denatured proteins and refold them. In addition, molecular chaperones, especially Hsp70, protect the brain and heart from severe ischemia. In these respects, there are expectations for the use of molecular chaperones for protection against and therapeutic treatment of inherited diseases caused by protein misfolding. In this study, we review Hsp70 and Hsp40, and refer to the roles of these molecules in the synapse and cytoprotective functions of HSPs in stress tolerance and neurodegenerative diseases.