RESUMO
To date five ULBP/RAET (UL16-binding protein, also known as retinoic acid early transcript) genes, encoded on human chromosome 6q24.2-q25.3, have been shown to encode ligands of the activating immunoreceptor NKG2D. Here, we show that a sixth gene, ULBP6/RAET1L, is a polymorphic locus that expresses a functional transcript. ULBP6 had a more restricted expression profile in cell lines and primary human tissues than other NKG2D ligands, but expression was detected in several human papillomavirus-positive cervical carcinoma cell lines and was inducible on infection with human CMV. ULBP6 bound to recombinant NKG2D as well as the human CMV immune evasion molecule UL16. By confocal microscopy we show that UL16 retains ULBP6 inside the cell, preventing it from reaching the cell surface. Expression of ULBP6 on target cells induced a significant increase in NK-cell killing. Comparison of ULBP6 with ULBP4 and ULBP5 indicated that differences in recombinant NKG2D binding correlated with differences in NK-cell activation.
Assuntos
Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Células Matadoras Naturais/imunologia , Ativação Linfocitária/imunologia , Western Blotting , Proteínas Ligadas por GPI , Perfilação da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/genética , Microscopia Confocal , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The replication and transcriptional activator (Rta), encoded by ORF50 of gammaherpesviruses, initiates the lytic cycle of gene expression; therefore understanding the impact of Rta on viral and cellular gene expression is key to elucidating the transcriptional events governing productive infection and reactivation from latency. To this end, the impact of altering Rta transcription on viral and cellular gene expression was studied in the context of a whole virus infection. Recombinant murine gammaherpesvirus (MHV)-68 engineered to overexpress Rta greatly accelerated expression of specific lytic cycle ORFs, but repressed transcription of the major latency gene, ORF73. Increased expression of Rta accelerated the dysregulation in transcription of specific cellular genes when compared with cells infected with wild-type and revertant viruses. A subset of cellular genes was dysregulated only in cells infected with Rta-overexpressing virus, and never in those infected with non-overexpressing viruses. These data highlight the critical role of Rta abundance in governing viral and cellular gene transcription, and demonstrate the importance of understanding how the relative expression of ORF50 during the virus life cycle impacts on these processes.
Assuntos
Regulação Viral da Expressão Gênica , Proteínas Imediatamente Precoces/fisiologia , Rhadinovirus/fisiologia , Transativadores/fisiologia , Proteínas Virais/fisiologia , Animais , Perfilação da Expressão Gênica , Proteínas Imediatamente Precoces/genética , Camundongos , Células NIH 3T3 , Análise de Sequência com Séries de Oligonucleotídeos , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , RNA Viral/biossíntese , RNA Viral/genética , Rhadinovirus/genética , Transativadores/genética , Proteínas Virais/genética , Replicação ViralRESUMO
An effective host immune response to mycobacterial infection must control pathogen dissemination without inducing immunopathology. Constitutive overexpression of mycobacterial heat shock protein (myHsp70) is associated with impaired bacterial persistence, but the immune-mediated mechanisms are unknown. We found that myHsp70, in addition to enhancing antigen delivery to human dendritic cells, signaled through the CCR5 chemokine receptor, promoting dendritic cell aggregation, immune synapse formation between dendritic cells and T cells, and the generation of effector immune responses. Thus, CCR5 acts as a pattern-recognition receptor for myHsp70, which may have implications for both the pathophysiology of tuberculosis and the use of myHsps in tumor-directed immunotherapy.