Rac3

Rac3 is a small GTPase of the Rac subfamily within the Rho family of GTPases. The RAC3 gene encodes the Rac3 protein in humans. Like other Rac proteins, Rac3 acts as a molecular switch, cycling between an active GTP-bound state and an inactive GDP-bound state, a process regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). In its active form, Rac3 modulates the actin cytoskeleton, promoting lamellipodia formation, cell spreading, and motility. It signals through downstream effectors, including p21-activated kinases (PAKs) and the WAVE regulatory complex, to control actin dynamics and gene expression.

Expression of RAC3 is enriched in neural tissue, with high levels in the brain during development and adolescence, and detectable but lower expression in other tissues. In the nervous system, Rac3 participates in neuronal morphogenesis, including dendritic spine formation and synaptic maturation, and may influence axon guidance and neuronal migration.

Clinical relevance is primarily explored in cancer biology and neurobiology. Altered RAC3 expression or activity has been reported in certain tumors, sometimes correlating with changes in cell motility and invasiveness in specific contexts. In neuroscience, dysregulation of Rac3 signaling is investigated for potential roles in neurodevelopmental and synaptic disorders, though the evidence is context-dependent.

RAC3 is related to other Rac family members, notably RAC1 and RAC2, which share overlapping functions but can have distinct expression patterns and roles.