Vav is a family of proteins involved in cell signalling. They act as guanine nucleotide exchange factors (GEFs) for small G proteins of the Rho family. [1] [2] GEF activity is mediated via module of tandem DH-PH domains. Vav proteins also appear to exhibit GEF-independent functions. Although it was originally thought that Vav proteins would only be present in multicellular organisms, [1] Vav family proteins have been observed in Choanoflagellates. [2]
Some functions of the Vav protein are important for the immune system. Specifically the ability of Vav to change the cytoskeletal structure of lymphocytes, which is particularly used to "aim" cytokines towards bound pathogens or cells. [3]
In humans there are three Vav proteins:
GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a protein domain common to many GTPases.
G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their activity is regulated by factors that control their ability to bind to and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). When they are bound to GTP, they are 'on', and, when they are bound to GDP, they are 'off'. G proteins belong to the larger group of enzymes called GTPases.
Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated structural domains have been shown to exhibit guanine nucleotide exchange activity. Some GEFs can activate multiple GTPases while others are specific to a single GTPase.
The Rho family of GTPases is a family of small signaling G proteins, and is a subfamily of the Ras superfamily. The members of the Rho GTPase family have been shown to regulate many aspects of intracellular actin dynamics, and are found in all eukaryotic kingdoms, including yeasts and some plants. Three members of the family have been studied in detail: Cdc42, Rac1, and RhoA. All G proteins are "molecular switches", and Rho proteins play a role in organelle development, cytoskeletal dynamics, cell movement, and other common cellular functions.
Transforming protein RhoA, also known as Ras homolog family member A (RhoA), is a small GTPase protein in the Rho family of GTPases that in humans is encoded by the RHOA gene. While the effects of RhoA activity are not all well known, it is primarily associated with cytoskeleton regulation, mostly actin stress fibers formation and actomyosin contractility. It acts upon several effectors. Among them, ROCK1 and DIAPH1 are the best described. RhoA, and the other Rho GTPases, are part of a larger family of related proteins known as the Ras superfamily, a family of proteins involved in the regulation and timing of cell division. RhoA is one of the oldest Rho GTPases, with homologues present in the genomes since 1.5 billion years. As a consequence, RhoA is somehow involved in many cellular processes which emerged throughout evolution. RhoA specifically is regarded as a prominent regulatory factor in other functions such as the regulation of cytoskeletal dynamics, transcription, cell cycle progression and cell transformation.
Rap guanine nucleotide exchange factor 3 also known as exchange factor directly activated by cAMP 1 (EPAC1) or cAMP-regulated guanine nucleotide exchange factor I (cAMP-GEFI) is a protein that in humans is encoded by the RAPGEF3 gene.
Proto-oncogene vav is a protein that in humans is encoded by the VAV1 gene.
RhoGEF domain describes two distinct structural domains with guanine nucleotide exchange factor (GEF) activity to regulate small GTPases in the Rho family. Rho small GTPases are inactive when bound to GDP but active when bound to GTP; RhoGEF domains in proteins are able to promote GDP release and GTP binding to activate specific Rho family members, including RhoA, Rac1 and Cdc42.
Rho guanine nucleotide exchange factor 7 is a protein that in humans is encoded by the ARHGEF7 gene.
A-kinase anchor protein 13 is an protein that in humans is encoded by the AKAP13 gene. This protein is also called AKAP-Lbc because it encodes the lymphocyte blast crisis (Lbc) oncogene, and ARHGEF13/RhoGEF13 because it contains a guanine nucleotide exchange factor (GEF) domain for the RhoA small GTP-binding protein.
Rho guanine nucleotide exchange factor 6 is a protein that, in humans, is encoded by the ARHGEF6 gene.
Dock180, also known as DOCK1, is a large protein involved in intracellular signalling networks. It is the mammalian ortholog of the C. elegans protein CED-5 and belongs to the DOCK family of Guanine nucleotide exchange factors (GEFs).
Guanine nucleotide exchange factor VAV2 is a protein that in humans is encoded by the VAV2 gene.
Rho guanine nucleotide exchange factor 12 is a protein that in humans is encoded by the ARHGEF12 gene. This protein is also called RhoGEF12 or Leukemia-associated Rho guanine nucleotide exchange factor (LARG).
RhoG is a small monomeric GTP-binding protein, and is an important component of many intracellular signalling pathways. It is a member of the Rac subfamily of the Rho family of small G proteins and is encoded by the gene RHOG.
Guanine nucleotide exchange factor VAV3 is a protein that in humans is encoded by the VAV3 gene.
Dock4, also known as DOCK4, is a large protein involved in intracellular signalling networks. It is a member of the DOCK-B subfamily of the DOCK family of guanine nucleotide exchange factors (GEFs) which function as activators of small G proteins. Dock4 activates the small G proteins Rac and Rap1.
Guanine nucleotide-binding protein subunit alpha-13 is a protein that in humans is encoded by the GNA13 gene.
Guanine nucleotide-binding protein subunit alpha-12 is a protein that in humans is encoded by the GNA12 gene.
DHR2, also known as CZH2 or Docker2, is a protein domain of approximately 450-550 amino acids that is present in the DOCK family of proteins. This domain functions as a guanine nucleotide exchange factor (GEF) domain for small G proteins of the Rho family. DHR2 domains bear no significant similarity to the well described DH domain present in other RhoGEFs such as Vav, P-Rex and TRIO. Indeed, the most divergent mammalian DHR2 domains share only 16-17% sequence similarity.