GMIP (GEM interacting protein) is a GTPase activating protein that regulates RhoA-mediated cytoskeletal dynamics and cellular signaling pathways. GMIP functions as a key component in the Gem/GMIP/RhoA signaling cascade, where it acts downstream of Gem GTPase to modulate cortical actin remodeling and spindle positioning during mitosis 1. The protein stimulates RhoA GTPase activity, leading to negative regulation of small GTPase-mediated signal transduction pathways 1. During early mitosis, GMIP accumulates at the cell cortex and is essential for proper spindle positioning through RhoA activation - knockdown of GMIP can rescue spindle defects caused by Gem overexpression 1. Beyond its role in cell division, GMIP appears to have neurological significance, with genetic variants in the GMIP gene showing association with major depressive disorder in Japanese populations 2. A promoter polymorphism (-525G/A) associated with depression risk demonstrates functional consequences, with the risk allele showing decreased transcriptional activity 2. GMIP also contains conserved ARIES domains that may participate in interferon signaling pathways 3. These findings establish GMIP as a critical regulator of cytoskeletal organization with potential implications in neuropsychiatric disorders.