Guanine nucleotide dissociation inhibitor (GDI) which functions as a receptor-independent activator of heterotrimeric G-protein signaling. Keeps G(i/o) alpha subunit in its GDP-bound form thus uncoupling heterotrimeric G-proteins signaling from G protein-coupled receptors. Controls spindle orientation and asymmetric cell fate of cerebral cortical progenitors. May also be involved in macroautophagy in intestinal cells. May play a role in drug addiction. Interacts with GNAI1 and GNAI2 preferentially in their GDP-bound state. May also interact with GNAO1. Interacts with INSC/inscuteable and FRMPD1 (By similarity). Interacts with GNAI3. Interacts with STK11/LKB1 and MACF1. Expressed in neural progenitor cells (at protein level). Expressed in brain at 14 dpc. The GoLoco domains are essential for the GDI activity toward G(i/o) alpha. The GoLoco domains mediate interaction with G(i/o) alpha (By similarity). Phosphorylation regulates interaction with G(i/o) alpha. Belongs to the GPSM family. Truncated N-terminus. Truncated N-terminus.