Constitutive activation of NF-kappa B and secretion of interleukin-8 induced by the G protein-coupled receptor of Kaposi's sarcoma-associated herpesvirus involve G alpha(13) and RhoA.
The Kaposi's sarcoma herpesvirus (KSHV) open reading frame 74 encodes a G protein-coupled receptor (GPCR) for chemokines. Exogenous expression of this constitutively active GPCR leads to cell transformation and vascular overgrowth characteristic of Kaposi's sarcoma. We show here that expression of KSHV-GPCR in transfected cells results in constitutive transactivation of nuclear factor kappa B (NF-kappa B) and secretion of interleukin-8, and this response involves activation of G alpha(13) and RhoA. The induced expression of a NF-kappa B luciferase reporter was partially reduced by pertussis toxin and the G beta gamma scavenger transducin, and enhanced by co-expression of G alpha(13) and to a lesser extent, G alpha(q). These results indicate coupling of KSHV-GPCR to multiple G proteins for NF-kappa B activation. Expression of KSHV-GPCR led to stress fiber formation in NIH 3T3 cells. To examine the involvement of the G alpha(13)-RhoA pathway in KSHV-GPCR-mediated NF-kappa B activation, HeLa cells were transfected with KSHV-GPCR alone and in combination with the regulator of G protein signaling (RGS) from p115RhoGEF or a dominant negative RhoA(T19N). Both constructs, as well as the C3 exoenzyme from Clostritium botulinum, partially reduced NF-kappa B activation by KSHV-GPCR, and by a constitutively active G alpha(13)(Q226L). KSHV-GPCR-induced NF-kappa B activation is accompanied by increased secretion of IL-8, a function mimicked by the activated G alpha(13) but not by an activated G alpha(q)(Q209L). These results suggest coupling of KSHV-GPCR to the G alpha(13)-RhoA pathway in addition to other G proteins.
Shepard
L W
LW
Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
Yang
M
M
Xie
P
P
Browning
D D
DD
Voyno-Yasenetskaya
T
T
Kozasa
T
T
Ye
R D
RD
D004268:DNA-Binding Proteins / Q000378:metabolism*; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D015654:Herpesvirus 6, Human / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012514:Sarcoma, Kaposi / Q000821:virology; D015398:Signal Transduction; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D004268:DNA-Binding Proteins; D016209:Interleukin-8; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D019204:GTP-Binding Proteins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020742:rhoA GTP-Binding Protein