title: Kaposi's sarcoma-associated herpesvirus induces Nrf2 during de novo infection of endothelial cells to create a microenvironment conducive to infection.
abstract: Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS) and primary effusion B-cell lymphoma. KSHV induces reactive oxygen species (ROS) early during infection of human dermal microvascular endothelial (HMVEC-d) cells that are critical for virus entry. One of the downstream targets of ROS is nuclear factor E2-related factor 2 (Nrf2), a transcription factor with important anti-oxidative functions. Here, we show that KS skin lesions have high Nrf2 activity compared to healthy skin tissue. Within 30 minutes of de novo KSHV infection of HMVEC-d cells, we observed Nrf2 activation through ROS-mediated dissociation from its inhibitor Keap1, Ser-40 phosphorylation, and subsequent nuclear translocation. KSHV binding and consequent signaling through Src, PI3-K and PKC-ζ were also important for Nrf2 stability, phosphorylation and transcriptional activity. Although Nrf2 was dispensable for ROS homeostasis, it was essential for the induction of COX-2, VEGF-A, VEGF-D, Bcl-2, NQO1, GCS, HO1, TKT, TALDO and G6PD gene expression in KSHV-infected HMVEC-d cells. The COX-2 product PGE2 induced Nrf2 activity through paracrine and autocrine signaling, creating a feed-forward loop between COX-2 and Nrf2. vFLIP, a product of KSHV latent gene ORF71, induced Nrf2 and its target genes NQO1 and HO1. Activated Nrf2 colocalized with the KSHV genome as well as with the latency protein LANA-1. Nrf2 knockdown enhanced ORF73 expression while reducing ORF50 and other lytic gene expression without affecting KSHV entry or genome nuclear delivery. Collectively, these studies for the first time demonstrate that during de novo infection, KSHV induces Nrf2 through intricate mechanisms involving multiple signal molecules, which is important for its ability to manipulate host and viral genes, creating a microenvironment conducive to KSHV infection. Thus, Nrf2 is a potential attractive target to intervene in KSHV infection and the associated maladies.
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Olsi
authors.initials: O
authors.lastname: Gjyshi
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Virginie
authors.initials: V
authors.lastname: Bottero
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Mohanan Valliya
authors.initials: MV
authors.lastname: Veettil
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Sujoy
authors.initials: S
authors.lastname: Dutta
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Vivek Vikram
authors.initials: VV
authors.lastname: Singh
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Leela
authors.initials: L
authors.lastname: Chikoti
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America.
authors.forename: Bala
authors.initials: B
authors.lastname: Chandran
mesh_terms: D051546:Cyclooxygenase 2 / Q000378:metabolism; D042783:Endothelial Cells / Q000821:virology*; D019288:Herpesvirus 8, Human; D006801:Humans; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D012514:Sarcoma, Kaposi / Q000821:virology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D053586:Virus Internalization
chemical_list: D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D017382:Reactive Oxygen Species; D042461:Vascular Endothelial Growth Factor A; D051546:Cyclooxygenase 2