Correct protein folding is an important factor, for the
translocation of newly synthesised proteins to specific
subcellular compartments, extracellular matrix or to
biological fluids. This process is regulated by a group
of specific proteins, referred to as chaperones. Many
stress conditions, such as oxygen or glucose
deprivation, slow down the folding process and cause
accumulation of unfolded/misfolded proteins in the
cell. Molecular chaperones are induced in these
conditions; with some named as oxygen-regulated
proteins (ORPs). These bind to unfolded / misfolded
proteins to facilitate correct assembly. ORP 150 is
the subject of this study. Hypoxia results in an
enhancement of ORP 150 expression in several
tumour cell lines cultured in vitro. HeLa cells grown in
hypoxic conditions (despite an intensive expression
of ORP 150) demonstrate higher rates of apoptosis
in comparison to those cultured in normoxic
conditions. Furthermore, the inhibition of ORP 150
synthesis by transfection of these cells with a specific siRNA resulted in an intensification of apoptosis, as
indicated by specific markers of this process; the
enhancement of poly ADP-ribose protein cleavage
and the increase in Bim protein expression. We
conclude from our study that the increase in ORP
150 synthesis protects the cells against the proapoptotic
effect of hypoxia.