No abstract

Abstract:: Pathophysiologic conditions of neurodegenerative diseases are unquestionably related to protein misfolding. The accumulation of misfolded proteins into relatively ordered structures such as fibrillar intracellular and extracellular amyloids results in tissue lesions that lead to neuronal loss and brain damage. In these pathologies, the occurrence of protein aggregates suggests certain inefficient or insufficient cellular response of those molecular chaperones that should properly assist the folding of the client proteins. In this regard, all the experimental models for neurodegenerative diseases have demonstrated that the overexpression of molecular chaperones provide effective neuroprotection. A subset of these molecular chaperones corresponds to a group of proteins that exhibit peptidylprolyl isomerase enzymatic activity, the immunophilins. Most of the family members of the latter group were first described as responsible of the immunosuppressive response or they were reported as members of the chaperone complex associated with HSP90 in steroid receptor oligomers. In this article we review some aspects of the liaison between molecular chaperones and neurodegenerative diseases, in particular heat-shock proteins and immunophilins with demonstrated influence in the proper function of mitochondria. This article is intended to address a field that represents a yet critical unmet clinical need for the development of neuroprotective molecules focused on potentially novel molecular targets.

Glucocorticoid steroids play cardinal roles during the life span of an individual modulating almost all aspects of the physiology, including metabolism of carbohydrates, lipids and amino acids, as well as the immune response, neurological biology, stress adaptation, apoptosis, cell division, cell fate, inflammatory responses, etc. Glucocorticoids exert their biological effects by activation of the glucocorticoid receptor (GR), a bona fide ligand-activated transcription factor belonging to the nuclear receptor superfamily. The GR is expressed in virtually all cells of the human body showing isoformic versions and also transcription variants. GR forms oligomeric heterocomplexes that include the 90-kDa heat-shock protein (Hsp90) as an essential hub of the chaperone oligomer. The nature of the chaperones associated to this heterocomplex are responsible for the modulation of the subcellular localization of the GR and its biological actions in a given tissue or cell type. In this sense, the discovery that immunophilins containing tetratricopeptide repeats (TPR) domains are responsible of the GR cytoplasmic transport mechanism and the nuclear retention half-time of the receptor opened new trends in our understanding of its complex mechanism of action. Because the properties of GR ligands influence these protein-protein interactions, specific steroid•receptor complexes may confer the GR different features providing new therapeutic opportunities to manage disease. In this article we analyze multiple aspects of the GR mechanism of action, some properties of the GR isoforms, and the latest findings revealing the roles of Hsp90-binding immunophilins to manage the glucocorticoid biological response.