The Rho Family Guanine Nucleotide Exchange Factor Vav-2 Regulates the Development of Cell-Mediated Cytotoxicity

Abstract

Previous pharmacologic and genetic studies have demonstrated a critical role for the low molecular weight GTP-binding protein RhoA in the regulation of cell-mediated killing by cytotoxic lymphocytes. However, a specific Rho family guanine nucleotide exchange factor (GEF) that activates this critical regulator of cellular cytotoxicity has not been identified. In this study, we provide evidence that the Rho family GEF, Vav-2, is present in cytotoxic lymphocytes, and becomes tyrosine phosphorylated after the cross-linking of activating receptors on cytotoxic lymphocytes and during the generation of cell-mediated killing. In addition, we show that overexpression of Vav-2 in cytotoxic lymphocytes enhances cellular cytotoxicity, and this enhancement requires a functional Dbl homology and Src homology 2 domain. Interestingly, the pleckstrin homology domain of Vav-2 was found to be required for enhancement of killing through some, but not all activating receptors on cytotoxic lymphocytes. Lastly, although Vav and Vav-2 share significant structural homology, only Vav is able to enhance nuclear factor of activated T cells–activator protein 1–mediated gene transcription downstream of the T cell receptor. These data demonstrate that Vav-2, a Rho family GEF, differs from Vav in the control of certain lymphocyte functions and participates in the control of cell-mediated killing by cytotoxic lymphocytes.

Rac Activation Induces NADPH Oxidase Activity in Transgenic COS Cells, and the Level of Superoxide Production Is Exchange Factor-dependent

“…Our results are also consistent with evidence suggesting differential regulation of downstream functions by the hematopoietic-specific Vav1 and widely expressed Vav2 isoforms, which are large multidomain proteins and only 55% homologous (74). In Jurkat T cells, antigeninduced activation of nuclear factor of activated T-cells-or NFB-dependent transcriptional pathways is strongly potentiated by overexpression of Vav1 but not Vav2 (75,76). Furthermore, studies of Vav-deficient mice indicate that Vav1 and Vav2 differentially regulate various lymphocyte functions (74,77,78).…”

Regulation of NK Cell-Mediated Cytotoxicity by the Adaptor Protein 3BP2

“…This difference may potentially cause a different binding specificity of the two SH2 domains for phosphotyrosine-containing proteins. We have previously shown that both Vav-1 and Vav-2 overexpression increases cell-mediated cytotoxicity in NK and T lymphocytes (9,24). However, Vav-1, but not Vav-2, selectively controls the NFAT/AP-1-dependent transcription in T cells (24), which indicates that the two isoforms do not have simply a redundant function.…”

SH2-containing inositol phosphatase (SHIP-1) transiently translocates to raft domains and modulates CD16-mediated cytotoxicity in human NK cells

“…38 Notably, rac1, ERK1/2 effectors, and Ca ϩϩ elevation critically control cytolytic granule polarization and exocytosis. 9,19,[39][40][41][42][43] Our results demonstrate that SHIP-1 could limit activation signals necessary for CD16-dependent cytotoxic function. Overexpression of SHIP-WT reduced CD16-mediated cytotoxicity and the functional catalytic domain of SHIP-1 is required, in that overexpression of the phosphatase inactive mutant did not affect the cytotoxic function.…”