Plasma membrane-targeted Raf kinase activates NF-kappaB and human immunodeficiency virus type 1 replication in T lymphocytes.
J Virol
; 72(4): 2788-94, 1998 Apr.
Article
en En
| MEDLINE
| ID: mdl-9525598
ABSTRACT
Increasing evidence points to a role of the mitogenic Ras/Raf/MEK/ERK signaling cascade in regulation of human immunodeficiency virus type 1 (HIV-1) gene expression. Stimulation of elements of this pathway leads to transactivation of the HIV-1 promoter. In particular, the NF-kappaB motif in the HIV long terminal repeat (LTR) represents a Raf-responsive element in fibroblasts. Regulation of the Raf kinase in T cells differs from findings with a variety of cell lines that the catalytic domain of Raf (Raf(delta26-303)) shows no activity. In this study, we restored the activity of the kinase in T cells by fusing its catalytic domain to the CAAX motif (-Cx) of Ras, thus targeting the enzyme to the plasma membrane. Constitutive activity of Raf was demonstrated by phosphorylation of mitogen-activated protein kinase kinase (MEK) and endogenous mitogen-activated protein kinase 1/2 (ERK1/2) in A3.01 T cells transfected with Raf(delta26-303)-Cx. Membrane-targeted Raf also stimulates NF-kappaB, as judged by kappaB-dependent reporter assays and enhanced NF-kappaB p65 binding on band shift analysis. Moreover, we found that active Raf transactivates the HIV(NL4-3) LTR in A3.01 T lymphocytes and that dominant negative Raf (C4) blocked 12-O-tetradecanoylphorbol-13-acetate induced transactivation. When cotransfected with infectious HIV(NL4-3) DNA, membrane-targeted Raf induces viral replication up to 10-fold over basal levels, as determined by the release of newly synthesized p24gag protein. Our study clearly demonstrates that the activity of the catalytic domain of Raf in A3.01 T cells is dependent on its cellular localization. The functional consequences of active Raf in T lymphocytes include not only NF-kappaB activation and transactivation of the HIV(NL4-3) LTR but also synthesis and release of HIV particles.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Linfocitos T
/
FN-kappa B
/
VIH-1
/
Proteínas Proto-Oncogénicas c-raf
/
Proteínas Quinasas Activadas por Mitógenos
/
Quinasa 1 de Quinasa de Quinasa MAP
Límite:
Humans
Idioma:
En
Revista:
J Virol
Año:
1998
Tipo del documento:
Article
País de afiliación:
Alemania