Upregulation of cytosolic chaperonin CCT subunits during recovery from chemical stress that causes accumulation of unfolded proteins.

The chaperonin containing TCP-1 (CCT) is a molecular chaperone consisting of eight subunit species and assists in the folding of actin, tubulin and some other cytosolic proteins. We examined the stress response of CCT subunit proteins in mammalian cultured cells using chemical stressors that cause accumulation of unfolded proteins. Levels of CCT subunit proteins in HeLa cells were coordinately and transiently upregulated under continuous chemical stress with sodium arsenite. CCT subunit levels in several mammalian cell lines were also upregulated during recovery from chemical stress caused by sodium arsenite or a proline analogue, L-azetidine-2-carboxylic acid. Several unidentified proteins that were newly synthesized and associated with CCT were found to increase concomitantly with CCT subunits themselves and known substrates during recovery from the stress. These results suggest that CCT plays important roles in the recovery of cells from protein damage by assisting in the folding of proteins that are actively synthesized and/or renatured during this period.