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Description

Heat shock protein HSP 90-beta (UniProt: P34058, also known as Heat shock 84 kDa, HSP 84, HSP84) is encoded by the Hsp90ab1 (also known as Hsp84, Hspcb) gene (Gene ID: 301252) in rat. HSP90 is a ubiquitous chaperone protein with multiple functions in the cell. It promotes the maturation, structural maintenance and proper regulation of specific target proteins involved for instance in cell cycle control and signal transduction. HSP90 undergoes a functional cycle that is linked to its ATPase activity. This cycle probably induces conformational changes in the client proteins, such as transcription factors, hormone receptors, and protein kinases, thereby causing their activation. HSP90 is abundant protein in the cell and may account for up to 2% of the total cytosolic protein. HSP90 is considered to be absolutely essential for cell survival. Its anti-apoptotic activity involves the inhibition of Apaf-1 oligomerization and caspase activation. Apart from its chaperone activity, HSP90 also plays a role in the regulation of the transcription machinery. HSP90 and its co-chaperones modulate transcription by altering the steady-state levels of certain transcription factors in response to various physiological cues and also modulate the activity of certain epigenetic modifiers, such as histone deacetylases or DNA methyl transferases. HSP90 can also participate in the eviction of histones from the promoter region of certain genes and thereby turn on gene expression. Nitration of HSP90 results in decreased chaperone activity and intracellular release of the nitrated HSP90 is shown to induce induces death of PC12 cells. (Ref.: Ye, Y et al (2007). J. Biol. Chem. 282(9), 6324-6337).