RHOH
Description
The RHOH (ras homolog family member H) is a protein-coding gene located on chromosome 4.
RhoH (Ras homolog gene family, member H) is a small (~21 kDa) signaling G protein (more specifically a GTPase), and is a member of the Rac subfamily of the Rho family of GTPases. It is encoded by the gene RHOH. Expression of a chimeric transcript of LAZ3 and this gene has been reported as a result of the translocation t(3;4) in non-Hodgkin's lymphomas. Unlike most other small G proteins which are expressed ubiquitously, this gene is transcribed only in hemopoietic cells.
RhoH negatively regulates hematopoietic progenitor cell proliferation, survival, and migration. It plays a critical role in thymocyte development and T-cell receptor (TCR) signaling by mediating recruitment and activation of ZAP70. RhoH is required for phosphorylation of CD3Z, membrane translocation of ZAP70, and subsequent activation of ZAP70-mediated pathways. It is essential for efficient beta-selection and positive selection by promoting ZAP70-dependent phosphorylation of the LAT signalosome during pre-TCR and TCR signaling. RhoH is crucial for thymocyte maturation during the DN3 to DN4 transition and during positive selection. It also plays critical roles in mast cell function by facilitating phosphorylation of SYK in Fc epsilon RI-mediated signal transduction. RhoH is essential for the phosphorylation of LAT, LCP2, PLCG1, and PLCG2, and for Ca(2+) mobilization in mast cells. RhoH binds GTP but lacks intrinsic GTPase activity and is resistant to Rho-specific GTPase-activating proteins. It inhibits the activation of NF-kappa-B by TNF and IKKB and the activation of CRK/p38 by TNF. RhoH inhibits the activities of RAC1, RHOA, and CDC42. It negatively regulates leukotriene production in neutrophils.
RHOH is also known as ARHH, TTF.
