RHOH GTPase cycle

RHOH is constitutively bound to GTP and does not require a guanine nucleotide exchange factor (GEF) for activation. RHOH does not possess a GTPase activity, but has been reported to bind to a small number of GTPase activator proteins (GAPs), which possibly function as RHOH effectors. While RHOH is not found in the GDP bound state, GDP dissociation inhibitors (GDIs), still interact with RHOH, presumably affecting its translocation to the site of activity by sequestering it in the cytosol. Similar to RAC2, RHOH expression is also restricted to hematopoietic cells. RHOH function is required for T cell development and RHOH activity is regulated by posttranslational modifications downstream of activated T cell receptor (TCR). Following TCR activation, RhoH is degraded in lysosomes. In blood neutrophils from patients suffering from cystic fibrosis or eosinophils from patients with hypereosinophilic syndromes, an upregulation of RhoH expression has been found. RHOH is subject to mutations and translocations in lymphoma. Mutations in RHOH are associated with abnormal susceptibility to human beta-papillomavirus (beta-HPV) skin infections, which leads to epidermodysplasia verruciformis, a condition characterized by persistent flat warts or beta-HPV associated skin lesions.

Summary from Reactome (R-HSA-9013407), read 2026-09-23.