title: Vav1 and Ly-GDI two regulators of Rho GTPases, function cooperatively as signal transducers in T cell antigen receptor-induced pathways.
abstract: The Rho family GTPases are pivotal for T cell signaling; however, the regulation of these proteins is not fully known. One well studied regulator of Rho GTPases is Vav1; a hematopoietic cell-specific guanine nucleotide exchange factor critical for signaling in T cells, including stimulation of the nuclear factor of activated T cells (NFAT). Surprisingly, Vav1 associates with Ly-GDI, a hematopoietic cell-specific guanine nucleotide dissociation inhibitor of Rac. Here, we studied the functional significance of the interaction between Vav1 and Ly-GDI in T cells. Upon organization of the immunological synapse, both Ly-GDI and Vav1 relocalize to T cell extensions in contact with the antigen-presenting cell. Ly-GDI is phosphorylated on tyrosine residues following T cell receptor stimulation, and it associates with the Src homology 2 region of an adapter protein, Shc. In addition, the interaction between Ly-GDI and Vav1 requires tyrosine phosphorylation. Overexpression of Ly-GDI alone is inhibitory to NFAT stimulation and calcium mobilization. However, when co-expressed with Vav1, Ly-GDI enhances Vav1 induction of NFAT activation, phospholipase Cgamma phosphorylation, and calcium mobilization. Moreover, Ly-GDI does not alter the regulation of these phenomena when coexpressed with oncogenic Vav1. Since oncogenic Vav1 does not bind Ly-GDI, this suggests that the functional cooperativity of Ly-GDI and Vav1 is dependent upon their association. Thus, our data suggest that the interaction of Vav1 and Ly-GDI creates a fine tuning mechanism for the regulation of intracellular signaling pathways leading to NFAT stimulation.
authors.affiliation: Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Maya
authors.initials: M
authors.lastname: Groysman
authors.forename: Idit
authors.initials: I
authors.lastname: Hornstein
authors.forename: Andres
authors.initials: A
authors.lastname: Alcover
authors.forename: Shulamit
authors.initials: S
authors.lastname: Katzav
mesh_terms: D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D018797:Cell Cycle Proteins; D002462:Cell Membrane / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005822:Genetic Vectors; D020730:Guanine Nucleotide Dissociation Inhibitors; D006801:Humans; D006868:Hydrolysis; D015151:Immunoblotting; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010766:Phosphorylation; D011233:Precipitin Tests; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D018909:src Homology Domains
chemical_list: C569658:ARHGDIB protein, human; D000945:Antigens, Differentiation, T-Lymphocyte; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C496618:VAV1 protein, human; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D014443:Tyrosine; D010738:Type C Phospholipases; D020741:rho GTP-Binding Proteins; D002118:Calcium