Role of an Isoform of Zhangfei/CREBZF in the Apoptotic Pathway of the Unfolded Protein Response
The unfolded protein response (UPR) is a well conserved mechanism in eukaryotes that protects organisms from the damaging effects of endoplasmic reticulum (ER) stresses. Activation of the UPR will lead to two outcomes. It first attempts to restore cellular functions by enhancing protein folding capacity, inhibiting protein synthesis and promoting degradation of harmful proteins (the pro-survival pathway). However, if the stressful conditions are prolonged or severe, apoptosis will be induced (the pro-apoptotic pathway). The present study suggests that an isoform of the cellular protein Zhangfei (ZF, CREBZF) is linked to the pro-apoptotic pathway in the UPR by using DNA, protein and cell viability analyses. This isoform is known as the short-tail ZF (stZF). We demonstrated that stZF can be induced by prolonged ER stress. The protein of stZF is stable under ER stress and it has the ability to promote programmed cell death in the early stage of apoptosis through the induction of CHOP, a protein that plays a key role in the pro-apoptotic pathway of the UPR.