ARHGAP33 is a brain-enriched Rho GTPase-activating protein with multifaceted roles in intracellular trafficking and synaptic function. Mechanistically, ARHGAP33 interacts with SORT1 to regulate the intracellular trafficking of TrkB, a key neurotrophin receptor essential for synapse development 1. The protein also functions in epithelial cell polarization and apical cargo secretion, as demonstrated by CRISPR screening showing that ARHGAP33 knockout causes mislocalization of apical cargo proteins to late endosomes/lysosomes 2. Additionally, ARHGAP33 participates in Rho GTPase signaling pathways critical for hair cell function and hearing 3. Disease relevance is substantial. ARHGAP33 dysfunction is implicated in neuropsychiatric disorders; knockout mice exhibit impaired spine development and behavioral abnormalities reversible by TrkB pathway enhancement 1. Genetic variants in ARHGAP33 are associated with COVID-19 hospitalization severity 4, and the gene shows altered expression in testis tissue from infertile patients with nonobstructive azoospermia 5. ARHGAP33 variants may also contribute to antidepressant treatment response through neurotrophic pathways 6. Clinically, ARHGAP33 represents a candidate gene for understanding the molecular pathology of neuropsychiatric disorders, reproductive dysfunction, and complex disease susceptibility to infection and psychiatric conditions.