Capsaicin Induces ATF4 Translation with Upregulation of CHOP, GADD34 and PUMA.

Primary Effusion Lymphoma (PEL) is a rare and aggressive B-lymphoma caused by Kaposi's sarcoma-associated herpes virus (KSHV) infection that occurs in immunocompromised patients. PEL patients have a poor prognosis. KSHV modulates various cellular signaling pathways to maintain latent infection, and causes malignant conversion of host cells. We previously reported that capsaicin suppressed extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) signaling and induced apoptosis in PEL. Generally, cellular stress such as nutrient starvation, oxidation and virus infection induce CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) expression by activating transcription factor 4 (ATF4), however endoplasmic reticulum (ER) stress induces CHOP expression by both ATF4 and ATF6. CHOP is associated with apoptosis induction and upregulates growth arrest and DNA damage-inducible protein 34 (GADD34) and p53 up-regulated modulator of apoptosis (PUMA) mRNA expression. In this study, we found a new mechanism in which capsaicin induces apoptosis via ATF4-CHOP-PUMA. Capsaicin promoted transcriptional activation of CHOP, which increased mRNA expression of GADD34 and PUMA, resulting in PEL apoptosis. Furthermore, capsaicin increased ATF4 protein levels by promoting ATF4 translation, not transcription, and had no effect on ATF6-dependent transcriptional activation. In sum, capsaicin promotes ATF4 translation and transcriptional induction of CHOP, which results in PUMA expression and apoptosis in PEL cells.