Immunophilins comprise a family of intracellular proteins with peptidyl-prolyl-(cis/trans)-isomerase activity.
These foldases are abundant, ubiquitous, and able to bind immunosuppressant drugs, from which the term immunophilin
derives. Family members are found in abundance in virtually all organisms and subcellular compartments, and their amino
acid sequences are conserved phylogenetically. Immunophilins possess the ability to function as molecular chaperones favoring
the proper folding and biological regulation of their biological actions. Their ability to interact via their TPR domains
with the 90-kDa heat-shock protein, and through this chaperone, with several signalling cascade factors is of particular
importance. Among the family members, the highly homologous proteins FKBP51 and FKBP52 were first characterized
due to their ability to interact with steroid hormone receptors. Since then, much progress has been made in understanding
the mechanisms by which they regulate receptor signaling and the resulting roles they play not only in endocrine
processes, but also in cell architecture, neurodifferentiation, and tumor progression. In this article we review the most relevant
features of these two immunophilins and their potential as pharmacologic targets.
Keywords: FK506, FKBP51, FKBP52, Hsp70, Hsp90, Immunophilin, Peptidylprolyl isomerase, TPR.
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