Non-Structural Protein 2B of Human Rhinovirus 16 Activates Both PERK and ATF6 Rather Than IRE1 to Trigger ER Stress

Abstract

To understand the underlying mechanisms of endoplasmic reticulum (ER) stress caused by human rhinovirus (HRV) 16 and non-structural transmembrane protein 2B, the expressions of ER chaperone glucose-regulated protein 78 (GRP78) and three signal transduction pathways, including protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6) and inositol-requiring enzyme 1 (IRE1), were evaluated after HRV16 infection and 2B gene transfection. Our results showed that both HRV16 infection and 2B gene transfection increased the expression of ER chaperone GRP78, and induced phosphorylation of PERK and cleavage of ATF6 in a time-dependent manner. Our data also revealed that the HRV16 2B protein was localized to the ER membrane. However, both HRV16 infection and HRV16 2B gene transfection did not induce ER stress through the IRE1 pathway. Moreover, our results showed that apoptosis occurred in H1-HeLa cells infected with HRV16 or transfected with 2B gene accompanied with increased expression of CHOP and cleaved caspase-3. Taken together, non-structural protein 2B of HRV16 induced an ER stress response through the PERK and ATF6 pathways rather than the IRE1 pathway.

Rhinovirus and Innate Immune Function of Airway Epithelium

“…During cell proliferation and differentiation, the ER may be overloaded by molecular chaperones, folding enzymes and massive protein products causing ER stress. Furthermore, pathophysiological stress signals such as viral infection, accumulation of misfolded proteins, hypoxia ER-Ca 2 depletion can cause ER stress (Kaufman, 1999;Koumenis, 2006;Jheng et al, 2010;Song et al, 2019). To overcome the ER stress, the eukaryotic cells have developed an adaptive response known as unfolded protein response (UPR) to reduce the load of newly synthesized proteins and misfolded proteins by increased expression of molecular chaperones.…”

“…Many positive strand RNA viruses, including RV have been shown to cause UPR-related ER stress (Su et al, 2002;Tardif et al, 2004;Jheng et al, 2010). Recently RV was shown to increase the expression of GRP78 as early as 6 h post-infection, suggesting RV induces ER stress and this was associated with the activation of PERK and ATF6 arms of UPR, and also an increase in the expression of viral structural protein, VP2 (Song et al, 2019). Moreover, RV 2B protein, which participates in the processing of RV polypeptide during viral replication co-localized with ER membrane.…”

Biological Function and Application of Picornaviral 2B Protein: A New Target for Antiviral Drug Development

“…The majority of 2B proteins are localized to organelles, with predominant co-localization with the Golgi apparatus and the endoplasmic reticulum (ER) in CVB3, PV, and HRV14 (Figure 1) [36]. The HRV16 and FMDV 2B proteins are mainly localized to the ER, whereas the EMCV 2B protein is not localized to either the Golgi complex or the ER [28,36,37]. Seggewiss et al [38] found that the HAV 2B protein was not localized to the ER either but was involved in the amendment of the ER–Golgi apparatus intermediate compartment.…”

“…The 2B protein has also been shown to regulate apoptosis through the endogenous pathway, which can be divided into ER stress and the mitochondrial pathway, providing another potential mechanism of bypassing the host immune response to facilitate infection [32,37,44,45,48]. The Ca 2+ plays a pivotal role in ER stress-dependent apoptosis by regulating the flow between the ER and the mitochondria [45,61].…”

Penehyclidine Hydrochloride Alleviates Lipopolysaccharide-Induced Acute Lung Injury by Ameliorating Apoptosis and Endoplasmic Reticulum Stress

“…ER homeostasis can be improved by extended protein response (UPR). 13,14 Apoptosis is promoted by the properties of UPR as stress continues. 14 ERS-mediated apoptosis has been associated with a significant factor described as C/EBP homologous protein (CHOP).…”