Activation of p21-activated kinase 1-nuclear factor kappaB signaling by Kaposi's sarcoma-associated herpes virus G protein-coupled receptor during cellular transformation.
Kaposi's sarcoma-associated herpes virus (KSHV) contributes to the pathogenesis of Kaposi's sarcoma and primary effusion lymphomas. KSHV encodes a G protein-coupled receptor (KSHV-GPCR) that signals constitutively and transforms NIH3T3 cells. Here, we show that KSHV-GPCR transformation requires activation of the small G protein Rac1 and its effector, the p21-activated kinase 1 (Pak1). Either transient or sustained expression of KSHV-GPCR activated both Rac1 and Pak1. Furthermore, expression of dominant-negative mutants of Rac (RacN17) or Pak1 (PakR299, Pak-PID) inhibited KSHV-GPCR-induced focus formation and growth in soft agar. We also demonstrate that signaling from Pak1 to nuclear factor-kappaB (NFkappaB) is required for cell transformation induced by KSHV-GPCR. KSHV-GPCR induced transcriptional activation by NFkappaB. This process is inhibited by the PAK-PID, whereas reciprocally, expression of constitutively active Pak1 (PakL107F) activated NFkappaB comparably to KSHV-GPCR. The Pak-PID and RacN17 inhibited the KSHV-GPCR-induced phosphorylation of inhibitor of kappaB kinase-beta and inhibitor of kappaB-alpha, implying that it is Pak1-dependent phosphorylation and subsequent destruction of the inhibitor of kappaB proteins that allows NFkappaB activation. Finally, experiments with the KSHV-GPCR inverse agonist interferon-gamma-inducible protein-10, the Galpha(i) inhibitor pertussis toxin, and an inhibitor of phosphatidylinositol 3'-kinase, wortmannin, indicate that signaling through the Galpha(i) pathway and phosphatidylinositol 3'-kinase contributes to the cell transformation and NFkappaB activation induced by the KSHV-GPCR.
Dadke
Disha
D
Department of Pharmacology, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA.
Fryer
Benjamin H
BH
Golemis
Erica A
EA
Field
Jeffrey
J
D000818:Animals; D002472:Cell Transformation, Viral / Q000502:physiology*; D004789:Enzyme Activation; D019288:Herpesvirus 8, Human / Q000378:metabolism / Q000502:physiology*; D051550:I-kappa B Kinase; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D051550:I-kappa B Kinase; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D043562:Receptors, G-Protein-Coupled; D014409:Tumor Necrosis Factor-alpha; D020764:cdc42 GTP-Binding Protein; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; C515906:Pak1 protein, rat; C496564:Chuk protein, mouse; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse