RESUMO
Kaposi's sarcoma-associated herpesvirus (KSHV) K13/vFLIP (viral Flice-inhibitory protein) induces transcription of numerous genes through NF-κB activation, including pro-inflammatory cytokines, which contribute to the pathogenesis of Kaposi's sarcoma (KS). In this study, we report that KSHV vFLIP induces the expression of the NF-κB regulatory proteins A20, ABIN-1 and ABIN-3 (A20-binding NF-κB inhibitors) in primary human endothelial cells, and that KS spindle cells express A20 in KS tissue. In reporter assays, A20 strongly impaired vFLIP-induced NF-κB activation in 293T cells, but ABIN-1 and ABIN-3 did not. Mutational analysis established that the C-terminal domain (residues 427-790) is critical for A20 modulation of NF-κB, but the ubiquitin-editing OTU (ovarian tumor) domain is not. In functional assays, A20 inhibited vFLIP-induced expression of the chemokine IP-10, reduced vFLIP-induced cell proliferation and increased IKK1 protein levels. Thus, we demonstrate that A20 negatively regulates NF-κB activation directly induced by KSHV vFLIP. By attenuating excessive and prolonged vFLIP-induced NF-κB activation that could be harmful to KSHV-infected cells, A20 likely has an important role in the pathogenesis of KSHV-associated diseases, in which vFLIP is expressed.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Herpesvirus Humano 8/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , NF-kappa B/antagonistas & inibidores , Proteínas Nucleares/metabolismo , Sarcoma de Kaposi/virologia , Proteínas Virais/metabolismo , Animais , Quimiocina CXCL10/metabolismo , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/genética , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Herpesvirus Humano 8/genética , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/biossíntese , Peptídeos e Proteínas de Sinalização Intracelular/genética , Camundongos , NF-kappa B/genética , NF-kappa B/metabolismo , Proteínas Nucleares/biossíntese , Proteínas Nucleares/genética , Proteínas/genética , Proteínas/metabolismo , Sarcoma de Kaposi/genética , Sarcoma de Kaposi/metabolismo , Sarcoma de Kaposi/patologia , Transdução Genética , Transfecção , Proteína 3 Induzida por Fator de Necrose Tumoral alfa , Proteínas Virais/antagonistas & inibidores , Proteínas Virais/genéticaRESUMO
Roll-out of combination antiretroviral therapy (cART) in South Africa should impact on AIDS-associated Kaposi's sarcoma (KS). Government provision began in 2003, with 23% coverage for World Health Organization (WHO) stage IV AIDS in 2006. To assess the effect of cART availability on KS management, we evaluated records from 701 KS patients seen at a tertiary oncology centre in KwaZulu-Natal, South Africa, from 1995 to 2006. Associations between cART use and measures of KS care were evaluated. cART availability was 0% prior to 2001, 9.6% (2001-2003) and 44% (2004-2006). Documentation of HIV status increased incrementally from 65% to 92%. cART was associated with chemotherapy administration: 56% on cART versus 17% not on cART (P < 0.001); and less loss to follow-up, 13% on cART versus 38% not on cART (P < 0.001). cART availability improves the care of AIDS-associated KS. Further increases in cART availability for this population are needed in South Africa.
