NFAT5, a constitutively nuclear NFAT protein that does not cooperate with Fos and Jun

NFAT1 enhances HIV-1 gene expression in primary human CD4 T cells

Cyclosporin A (CsA) is a potent inhibitor of the NFAT family of transcription factors that enhance T cell activation. The observation that human immunodeficiency virus type 1 (HIV-1)-positive transplant recipients have a reduced HIV-1 viral burden during treatment with CsA suggested that NFAT may play a direct role in enhancing transcription of the HIV-1 viral genome. Two sets of NFAT binding sites were identified in the HIV-1 long terminal repeat (LTR) promoter by in vitro footprinting with full-length recombinant NFAT protein, and gel shift analysis of nuclear protein from polyclonally activated primary CD4 T cells revealed specific binding of NFAT1 to the NFkappaB binding sites of the HIV-1 LTR. Activation of primary CD4 T cells transiently transfected with a HIV-1 LTR luciferase reporter plasmid, lacking the NFAT binding sites in the upstream putative negative regulatory element but maintaining the NFkappaB/NFAT sites, demonstrated increased HIV-1 gene expression when cotransfected with a NFAT1 expression vector. Moreover, CsA, FK506, and a dominant-negative NFAT1 protein independently inhibited HIV-1 LTR promoter activity in CD4 T cells stimulated with phorbol ester and calcium ionophore. In primary human CD4 T cells, CsA also inhibited promoter activity directed by multimers of binding sites for NFAT, while having no effect on NFkappaB multimer-driven promoter activity. Increasing NFAT1 levels in CD4 T cells transiently transfected with a HIV-1 provirus also increased p24 protein expression. Thus, NFAT may be a target for prevention of HIV-1 LTR-directed gene expression in human CD4 T cells.

Cell fate decision: T-helper 1 and 2 subsets in immune responses

After activation CD4(+) helper T cells differentiate into T-helper (Th) 1 or Th2 effector cells. These two subsets are characterized by their distinct cytokine expression pattern and the immune function they mediate. Over the past years, a number of factors have been identified to affect helper T cell lineage determination, including antigen receptor, coreceptors and, most importantly, cytokine environment. In this review, we also summarize recent advancement in understanding of transcriptional and signaling regulation of the differentiation process. This knowledge will become important in the future to develop means in treating immune disorders.

Affinity-driven peptide selection of an NFAT inhibitor more selective than cyclosporin A

The flow of information from calcium-mobilizing receptors to nuclear factor of activated T cells (NFAT)-dependent genes is critically dependent on interaction between the phosphatase calcineurin and the transcription factor NFAT. A high-affinity calcineurin-binding peptide was selected from combinatorial peptide libraries based on the calcineurin docking motif of NFAT. This peptide potently inhibited NFAT activation and NFAT-dependent expression of endogenous cytokine genes in T cells, without affecting the expression of other cytokines that require calcineurin but not NFAT. Substitution of the optimized peptide sequence into the natural calcineurin docking site increased the calcineurin responsiveness of NFAT. Compounds that interfere selectively with the calcineurin-NFAT interaction without affecting calcineurin phosphatase activity may be useful as therapeutic agents that are less toxic than current drugs.