Expression of Endoplasmic Reticulum–Mediated Stress Proteins in FK506-Treated T-Lymphocytes

• Apoptotic signals are delivered to caspase-3, -9, or both in different cells via the death receptor (Fas/FasL), mitochondria (Bax/Bcl-2) or by the ER through initiators of caspase-8, -9, or -12. FK506-induced apoptosis was characterized by nuclear fragmentation and caspase 3 activation.
• Expression of Grp78 and Grp94/BiP, PERK, and CHOP proteins was also identified.
• The CHOP protein is a key protein in the ER stress protein–mediated apoptotic pathway. FK506 dose-dependently decreases Jurkat cell viability by activating apoptosis signaling and inducing ER stress proteins.

BackgroundFK506-induced apoptotic endoplasmic reticulum (ER)-mediated stress protein expression was investigated in Jurkat human T-lymphocytes.MethodsThe effect of FK506 on apoptosis and cell viability were examined. FK506-induced apoptosis was confirmed by nuclear fragmentation after DAPI staining. Expression of apoptotic ER-mediated stress proteins was examined by means of Western blotting of Grp78/BiP, Grp94, double-stranded RNA-dependent protein kinase (PKR)-like ER kinase (PERK), phosphor-PERK, CHOP/GADD153, and Bak. A flow cytometry analysis was performed after DAF-DA or DCF-DA staining. FK506-induced apoptosis was dose-dependent (10 nmol/L) and time-dependent (72 hours).ResultsGrp78/BiP and Grp94 expressions were increased 36 hours after FK506 treatment. Increased phospho-PERK expression was observed 6 hours after FK506 treatment and peak activation of phospho-PERK was observed at 36 hours. CHOP/GADD153 expression was increased 48 hours after FK506 treatment. Expression of iNOS after FK506 treatment began to increase at 12 hours, peaked at 24 hours, and decreased after 36 hours.ConclusionsFrom these results, we confirmed that FK506 induces apoptosis and acts dose- and time-dependently to decrease the viability of Jurkat cells through activation of apoptosis signaling and expression of apoptotic ER-mediated stress proteins.