Hexokinase 2 controls cellular stress response through localization of an RNA-binding protein

Abstract

Subcellular localization of RNA-binding proteins is a key determinant of their ability to control RNA metabolism and cellular stress response. Using an RNAi-based kinome-wide screen, we identified hexokinase 2 (HK2) as a regulator of the cytoplasmic accumulation of hnRNP A1 in response to hypertonic stress and human rhinovirus infection (HRV). We show that inhibition of HK2 expression or pharmacological inhibition of HK2 activity blocks the cytoplasmic accumulation of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), restores expression of B-cell lymphoma-extra large (Bcl-xL), and protects cells against hypertonic stress-induced apoptosis. Reduction of HK2 protein levels by knockdown results in decreased HRV replication, a delay in HRV-induced cell death, and a reduced number of infected cells, all of which can be rescued by forced expression of a cytoplasm-restricted hnRNP A1. Our data elucidate a novel role for HK2 in cellular stress response and viral infection that could be exploited for therapeutic intervention.

The multifarious roles of heterogeneous ribonucleoprotein A1 in viral infections

“…Courteau et al supported this and also showed that cytoplasmic localization of hnRNPA1 controlled and enhanced IRES‐mediated translation of viral proteins, thereby acting as an ITAF . Furthermore, down‐regulating hnRNPA1 or expressing a cytoplasmic restricted mutant of the protein (hnRNPA1 ΔM9) partially restored the block on viral translation . They also identified the role of hexokinase 2 (HK‐2) in controlling the nucleo‐cytoplasmic distribution of hnRNPA1 …”

“…For instance, in Sindbis virus, PEDV, EV‐71, and HRV infections, hnRNPA1 shows a pro‐viral effect which may be attributed to the role of this protein as an ITAF, positively regulating IRES mediated translation of viral RNAs. Likewise, in ARV infection, virus exploits the nucleo‐cytoplasmic machinery in place for trafficking hnRNPA1 via its interaction with transportin‐1 to indirectly translocate p17 through the NPC.…”

“…Cammas et al reported physical binding of hnRNPA1 to the 5′UTR region of human rhinovirus (HRV) IRES . Courteau et al supported this and also showed that cytoplasmic localization of hnRNPA1 controlled and enhanced IRES‐mediated translation of viral proteins, thereby acting as an ITAF . Furthermore, down‐regulating hnRNPA1 or expressing a cytoplasmic restricted mutant of the protein (hnRNPA1 ΔM9) partially restored the block on viral translation .…”

“…Furthermore, down‐regulating hnRNPA1 or expressing a cytoplasmic restricted mutant of the protein (hnRNPA1 ΔM9) partially restored the block on viral translation . They also identified the role of hexokinase 2 (HK‐2) in controlling the nucleo‐cytoplasmic distribution of hnRNPA1 …”

ERK8 is a novel HuR kinase that regulates tumour suppressor PDCD4 through a miR-21 dependent mechanism

“…Confocal microscopy was performed using the 60X objective with immersion oil (Olympus Fluoview FV1000, Richmond Hill, Ontario Canada). Quantification of HuR nuclear and cytoplasmic distribution was done as described previously [ 40 ] with some modifications. The images were analyzed on a Columbus Image Analysis Server (Perkin Elmer) using an embedded Acapella Image Analysis Software (Perkin Elmer) script.…”