BPIFB6 Regulates Secretory Pathway Trafficking and Enterovirus Replication

Abstract

Bactericidal/permeability-increasing protein (BPI) fold-containing family B, member 3 (BPIFB3) is an endoplasmic reticulum (ER)-localized host factor that negatively regulates coxsackievirus B (CVB) replication through its control of the autophagic pathway. Here, we show that another member of the BPIFB family, BPIFB6, functions as a positive regulator of CVB, and other enterovirus, replication by controlling secretory pathway trafficking and Golgi complex morphology. We show that similar to BPIFB3, BPIFB6 localizes exclusively to the ER, where it associates with other members of the BPIFB family. However, in contrast to our findings that RNA interference (RNAi)-mediated silencing of BPIFB3 greatly enhances CVB replication, we show that silencing of BPIFB6 expression dramatically suppresses enterovirus replication in a pan-viral manner. Mechanistically, we show that loss of BPIFB6 expression induces pronounced alterations in retrograde and anterograde trafficking, which correlate with dramatic fragmentation of the Golgi complex. Taken together, these data implicate BPIFB6 as a key regulator of secretory pathway trafficking and viral replication and suggest that members of the BPIFB family participate in diverse host cell functions to regulate virus infections. IMPORTANCEEnterovirus infections are associated with a number of severe pathologies, such as aseptic meningitis, dilated cardiomyopathy, type I diabetes, paralysis, and even death. These viruses, which include coxsackievirus B (CVB), poliovirus (PV), and enterovirus 71 (EV71), co-opt the host cell secretory pathway, which controls the transport of proteins from the endoplasmic reticulum to the Golgi complex, to facilitate their replication. Here we report on the identification of a novel regulator of the secretory pathway, bactericidal/permeability-increasing protein (BPI) fold-containing family B, member 6 (BPIFB6), whose expression is required for enterovirus replication. We show that loss of BPIFB6 expression correlates with pronounced defects in the secretory pathway and greatly reduces the replication of CVB, PV, and EV71. Our results thus identify a novel host cell therapeutic target whose function could be targeted to alter enterovirus replication.T ransport of cargo from the endoplasmic reticulum (ER) to the Golgi complex requires a highly controlled system of proteins that function to regulate a variety of steps along the secretory pathway. These components must not only synchronize the loading of diverse cargo but also navigate the trafficking of this cargo to specific cellular compartments. The Golgi complex functions as a focal point of secretory pathway trafficking as it controls not only the anterograde trafficking of newly synthesized proteins from the ER to the cell membrane but also must facilitate the retrograde trafficking of surface-associated molecules from the plasma membrane back to the ER. Vesicles trafficking along the secretory pathway target their cargo to the Golgi complex via the use of distinct tethering machinery, suc...

Changes in salivary analytes in canine parvovirus: A high-resolution quantitative proteomic study

“…Although little is known about LCN9, a related protein, neutrophil gelatinase-associated lipocalin, NGAL, has been associated with bacterial infection in humans [47][48][49]. BPiFB2 belongs to a family of proteins considered as a key component of the innate immune response against Gram-negative bacteria [50], but the physiological functions of the BPIFB family still remain largely unknown [51]. Despite this, a previous study on BPIFB2 has reported the involvement of BPIFB proteins regulating enterovirus infection, with BPIFB6 assisting the enterovirus replication by controlling secretory pathway trafficking and Golgi complex morphology [51].…”

Enteroviruses infect human enteroids and induce antiviral signaling in a cell lineage-specific manner

“…Gene expression was determined based on a ΔC Q method (C Q is the Bio-Rad standard for cycle at point of quantification and is equivalent to C T ), normalized to the sample's C Q for human actin. Primer sequences for actin, MUC17, NAALADL1, CVB, E11, and EV71 have been previously described (17,18). All primer sequences used in the study are located in Table S1.…”

“…Experiments were performed with CVB3 (RD), EV-71 (GDV083), or E11 (Gregory) that were expanded as described previously (17). For enteroid infections, wells (containing ∼100 enteroids) were infected with 10 6 pfu of the indicated virus.…”

BPIFB3 facilitates flavivirus infection by controlling RETREG1-dependent reticulophagy

“…We showed previously that BPIFB3 localizes to domains enriched for the ER sheet marker 156 CLIMP63 (26). Therefore, we sought to examine whether BPIFB3 is involved in regulating ER 157 morphology or turnover during flavivirus infection.…”

“…Despite the high degree of predicted structural 342 homology, BPIFB3 localizes to the ER and is not secreted (23). Of the other members of the 343 family, BPIFB2 and BPIFB6 are also ER localized, however neither appear to regulate autophagy 344 (26) (26). Of the related proteins, BPIFB6 is the only protein to 348 be characterized, and has been demonstrated to regulate secretory trafficking and Golgi 349 morphology (26).…”