Sperm associated antigen 9 promotes oncogenic KSHV-encoded interferon regulatory factor-induced cellular transformation and angiogenesis by activating the JNK/VEGFA pathway

Abstract

Kaposi's sarcoma (KS), caused by Kaposi's sarcoma-associated herpesvirus (KSHV), is a highly angioproliferative disseminated tumor of endothelial cells commonly found in AIDS patients. We have recently shown that KSHV-encoded viral interferon regulatory factor 1 (vIRF1) mediates KSHV-induced cell motility (PLoS Pathog. 2019 Jan 30;15(1):e1007578). However, the role of vIRF1 in KSHV-induced cellular transformation and angiogenesis remains unknown. Here, we show that vIRF1 promotes angiogenesis by upregulating sperm associated antigen 9 (SPAG9) using two in vivo angiogenesis models including the chick chorioallantoic membrane assay (CAM) and the matrigel plug angiogenesis assay in mice. Mechanistically, vIRF1 interacts with transcription factor Lef1 to promote SPAG9 transcription. vIRF1-induced SPAG9 promotes the interaction of mitogen-activated protein kinase kinase 4 (MKK4) with JNK1/2 to increase their phosphorylation, resulting in enhanced VEGFA expression, angiogenesis, cell proliferation and migration. Finally, genetic deletion of ORF-K9 from KSHV genome abolishes KSHV-induced cellular transformation and impairs angiogenesis. Our results reveal that vIRF1 transcriptionally activates SPAG9 expression to promote angiogenesis and tumorigenesis via activating JNK/VEGFA signaling. These novel findings define the mechanism of KSHV induction of the SPAG9/JNK/ VEGFA pathway and establish the scientific basis for targeting this pathway for treating KSHV-associated cancers.

CircRNA ARFGEF1 functions as a ceRNA to promote oncogenic KSHV-encoded viral interferon regulatory factor induction of cell invasion and angiogenesis by upregulating glutaredoxin 3

“…To identify cellular circRNAs regulated by KSHV vIRF1, an endothelial cell line EA.hy926 was either treated with PBS, or infected with 3 MOI of KSHV_WT virus or vIRF1_mut virus for 3 days [ 16 , 17 ]. We characterized circRNAs profiles in these cells by total RNA-sequencing.…”

“…We found that vIRF1 activated circARFGEF1 promoter activity ( Fig 2G ). Our recent studies reported that vIRF1 interacted with transcription factor Lef1 to bind to the promoters of CDCP1 and SPAG9 genes, and enhance their transcriptions and expressions [ 9 , 17 ]. Here, we first overexpressed Lef1, and found that circARFGEF1 transcription was significantly enhanced by Lef1 ( Fig 2H ).…”

“…Our recent reports showed that vIRF1 promoted endothelial cell migration, invasion, proliferation, angiogenesis and cellular transformation [ 9 , 16 , 17 ]. We asked whether vIRF1-upregulated circARFGEF1 was involved in this process.…”

“…vIRF1 directly binds to a mitophagy receptor, NIX, on the mitochondria and activates NIX-mediated mitophagy to promote mitochondrial clearance, resulting in enhanced KSHV productive replication [ 15 ]. Although we and others have shown that vIRF1 promotes cell migration, invasion, proliferation, angiogenesis, cellular transformation and tumorigenesis in vitro and in vivo [ 9 , 12 , 16 , 17 ], the underlying mechanisms of vIRF1-mediated tumor pathogenesis still remain to be explored.…”

Molecular Virology of KSHV in the Lymphocyte Compartment—Insights From Patient Samples and De Novo Infection Models

“…KSHV encodes four viral interferon regulatory factors (vIRFs). These proteins have minimal homology to human IRFs, but vIRF1, vIRF2, and vIRF3 are known to bind DNA elements similar to their human IRF counterparts (Lubyova and Pitha, 2000;Park et al, 2007;Hu et al, 2016) vIRFs exert their regulatory role at varying levels ranging from hampering the antiviral interferon response to inhibition of signaling pathways to control the function of cellular proteins, thereby interfering with the cellular processes such as apoptosis (Rivas et al, 2001;Nakamura et al, 2001;Lee et al, 2009) proliferation and angiogenesis (Wies et al, 2008;Li et al, 2019;Li et al, 2020) vIRF3 (LANA-2) expression is detected in nearly all virus infected cells in PEL and MCD tumors, and vIRF3 is a bona fide oncogene which can inhibit the function of p53. Moreover, among the KSHV vIRFs, the function of vIRF3 is thought to be B cellspecific.…”