The Kaposi's Sarcoma-Associated Herpesvirus (KSHV)-Induced 5-Lipoxygenase-Leukotriene B4 Cascade Plays Key Roles in KSHV Latency,Monocyte Recruitment,and Lipogenesis

Kaposi''s sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi''s sarcoma (KS) and primary effusion lymphoma (PEL). KS lesions are characterized by endothelial cells with multiple copies of the latent KSHV episomal genome, lytic replication in a low percentage of infiltrating monocytes, and inflammatory cytokines plus growth factors. We demonstrated that KSHV utilizes inflammatory cyclooxygenase 2/prostaglandin E₂ to establish and maintain latency (Sharma-Walia, N., A. G. Paul, V. Bottero, S. Sadagopan, M. V. Veettil, N. Kerur, and B. Chandran, PLoS Pathog 6:e1000777, 2010 [doi:10.1371/journal.ppat.1000777]). Here, we evaluated the role of 5-lipoxygenase (5LO) and its chemotactic metabolite leukotriene B4 (LTB4) in KSHV biology. Abundant staining of 5LO was detected in human KS tissue sections. We observed elevated levels of 5LO and high levels of secretion of LTB4 during primary KSHV infection of endothelial cells and in PEL B cells (BCBL-1 and BC-3 cells). Blocking the 5LO/LTB4 cascade inhibited viral latent ORF73, immunomodulatory K5, viral macrophage inflammatory protein 1 (MIP-1), and viral MIP-2 gene expression, without much effect on lytic switch ORF50, immediate early lytic K8, and viral interferon-regulatory factor 2 gene expression. 5LO inhibition significantly downregulated latent viral Cyclin and latency-associated nuclear antigen 2 levels in PEL cells. 5LO/LTB4 inhibition downregulated TH2-related cytokine secretion, elevated TH1-related cytokine secretion, and reduced human monocyte recruitment, adhesion, and transendothelial migration. 5LO/LTB4 inhibition reduced fatty acid synthase (FASN) promoter activity and its expression. Since FASN, a key enzyme required in lipogenesis, is important in KSHV latency, these findings collectively suggest that 5LO/LTB4 play important roles in KSHV biology and that effective inhibition of the 5LO/LTB4 pathway could potentially be used in treatment to control KS/PEL.     

膜去极化与cAMP在胰岛细胞株HIT中诱导CBP片段的转录活性

为了研究 Ｃ Ｂ Ｐ在胰岛 Ｈ Ｉ Ｔ 细胞中调节基因转录的机制,将不同的 Ｃ Ｂ Ｐ片段瞬时转染到细胞中,观察其转录活性．实验表明,在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ 均可诱导 Ｃ Ｂ Ｐ３０（ Ｃ Ｒ Ｅ Ｂ结合功能区）转录活性增强,并有协同效应． Ｐ Ｋ Ｃ对 Ｃ Ｂ Ｐ３０ 的转录活性无影响;与 Ｃ Ｒ Ｅ Ｂ有更强结合力的 Ｃ Ｂ Ｐ Ｋ Ｉ Ｘ Ｓ／ Ｂ（氨基酸序列短于 Ｃ Ｂ Ｐ３０ 的 Ｃ Ｒ Ｅ Ｂ结合功能区）其基本转录活性及膜去极化、ｃ Ａ Ｍ Ｐ诱导下的转录活性均比 Ｃ Ｂ Ｐ３０ 更强．反义 Ｃ Ｒ Ｅ Ｂ 的过度表达可降低 ｃ Ａ Ｍ Ｐ诱导的 Ｃ Ｂ Ｐ的转录活性．提示在胰岛 Ｈ Ｉ Ｔ 细胞中,膜去极化及 ｃ Ａ Ｍ Ｐ对共转录因子 Ｃ Ｂ Ｐ转录活性的调节作用通过 Ｃ Ｒ Ｅ Ｂ介导．