RESUMO
The stress-induced unfolded protein response (UPR) in the endoplasmic reticulum (ER) involves various signaling cross-talks and controls cell fate. B-cell receptor (BCR) signaling, which can trigger UPR, induces gammaherpesvirus lytic replication and serves as a physiological mechanism for gammaherpesvirus reactivation in vivo However, how the UPR regulates BCR-mediated gammaherpesvirus infection is unknown. Here, we demonstrate that the ER stressors tunicamycin and thapsigargin inhibit BCR-mediated murine gammaherpesvirus 68 (MHV68) lytic replication by inducing expression of the UPR mediator Bip and blocking activation of Akt, ERK, and JNK. Both Bip and the downstream transcription factor ATF4 inhibited BCR-mediated MHV68 lytic gene expression, whereas UPR-induced C/EBP homologous protein (CHOP) was required for and promoted BCR-mediated MHV68 lytic replication by suppressing upstream Bip and ATF4 expression. Bip knockout was sufficient to rescue BCR-mediated MHV68 lytic gene expression in CHOP knockout cells, and this rescue was blocked by ectopic ATF4 expression. Furthermore, ATF4 directly inhibited promoter activity of the MHV68 lytic switch transactivator RTA. Altogether, we show that ER stress-induced CHOP inhibits Bip and ATF4 expression and that ATF4, in turn, plays a critical role in CHOP-mediated regulation of BCR-controlled MHV68 lytic replication. We conclude that ER stress-mediated UPR and BCR signaling pathways are interconnected and form a complex network to regulate the gammaherpesvirus infection cycle.
Assuntos
Fator 4 Ativador da Transcrição/metabolismo , Linfócitos B/virologia , Estresse do Retículo Endoplasmático , Gammaherpesvirinae/fisiologia , Proteínas de Choque Térmico/metabolismo , Receptores de Antígenos de Linfócitos B/agonistas , Fator de Transcrição CHOP/metabolismo , Fator 4 Ativador da Transcrição/antagonistas & inibidores , Fator 4 Ativador da Transcrição/genética , Animais , Antivirais/farmacologia , Linfócitos B/efeitos dos fármacos , Linfócitos B/imunologia , Linfócitos B/metabolismo , Linhagem Celular Transformada , Chaperona BiP do Retículo Endoplasmático , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Gammaherpesvirinae/efeitos dos fármacos , Gammaherpesvirinae/crescimento & desenvolvimento , Regulação da Expressão Gênica/efeitos dos fármacos , Técnicas de Inativação de Genes , Proteínas de Choque Térmico/antagonistas & inibidores , Proteínas de Choque Térmico/genética , Lisogenia/efeitos dos fármacos , Camundongos , Chaperonas Moleculares/antagonistas & inibidores , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Regiões Promotoras Genéticas/efeitos dos fármacos , Receptores de Antígenos de Linfócitos B/metabolismo , Transdução de Sinais/efeitos dos fármacos , Tapsigargina/farmacologia , Fator de Transcrição CHOP/antagonistas & inibidores , Fator de Transcrição CHOP/genética , Tunicamicina/farmacologia , Proteínas Virais/antagonistas & inibidores , Proteínas Virais/genética , Proteínas Virais/metabolismo , Ativação Viral/efeitos dos fármacos , Replicação Viral/efeitos dos fármacosRESUMO
Quantum dots (QDs) have a great potential for applications in nanomedicine. However, a few studies showed that they also exhibited toxicity. We used Escherichia coli (E. coli) as the model to study the effect of CdTe QDs on the cell growth by microcalorimetric technique, optical density (OD(600)) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra. Three size aqueous-compatible CdTe QDs with maximum emission of 543 nm (green-emitting QDs, GQDs), 579 nm (yellow-emitting QDs, YQDs) and 647 nm (red-emitting QDs, RQDs) were tested. The growth rate constants (k) and half-inhibiting concentration (IC(50)) were calculated from the microcalorimetric data. The results indicated that CdTe QDs exhibited a dose-dependent inhibitory effect on cell growth. The order of toxicity is GQDs>YQDs>RQDs. The smaller the particle size of QDs is, the more toxicity it is. ATR-FTIR spectra indicated that the outer membrane of the cell was changed or damaged by the QDs, which may induce QDs and harmful by-products to enter into the cells. These could be one of the reasons that CdTe QDs have cytotoxic effects on E. coli.
