Plays an important role in mitotic spindle pole organization via its interaction with NUMA1 (PubMed:21816348). Required for cortical dynein-dynactin complex recruitment during metaphase (By similarity). Plays a role in metaphase spindle orientation (By similarity). Plays an important role in asymmetric cell divisions (PubMed:12571286, PubMed:21816348). Has guanine nucleotide dissociation inhibitor (GDI) activity towards G(i) alpha proteins, such as GNAI1 and GNAI3, and thereby regulates their activity (PubMed:22952234). Interacts with the dynein-dynactin complex; this interaction is inhibited in a PLK1-dependent manner (By similarity). Part of a spindle orientation complex at least composed of GNAI1, GPSM2 and NUMA1 (By similarity). Interacts with LLGL2 (By similarity). Interacts (via TPR repeat region) with INSC/inscuteable (PubMed:16094321, PubMed:21816348). Interacts (via TPR repeat region) with NUMA1 (via C-terminus); this interaction is direct, inhibited in a PLK1-dependent manner and promotes spindle pole organization (PubMed:21816348, PubMed:23318951, PubMed:23665171). INSC and NUMA1 compete for the same binding site, but INSC has higher affinity and can displace NUMA1 (in vitro) (PubMed:21816348). Interacts with GNAI2 (By similarity). Interacts (via GoLoco domains) with the GDP-bound form of GNAI1 and GNAI3; has much lower affinity for the GTP-bound form (PubMed:22952234, PubMed:23665171). Interaction with GDP-bound GNAI3 strongly enhances the affinity for NUMA1 (PubMed:23665171). Interacts (via TPR repeat region) with FRMPD1 (PubMed:23318951). INSC and FRMPD1 compete for the same binding site, but INSC has higher affinity and can displace FRMPD1 (in vitro) (PubMed:23318951). Interacts (via TPR repeat region) with FRMPD4. Identified in a complex with INSC and F2RL2/Par3 (By similarity). Interacts with TASOR (PubMed:31112734). Localizes in the cytoplasm during interphase and at cell cortex during metaphase. Colocalizes with NUMA1 to mitotic spindle poles. Localized at the central and lateral cell cortex regions in a RanGTP-dependent manner (By similarity). In horizontally retinal progenitor dividing cells, localized to the lateral cortical region (PubMed:26766442). In vertically retinal progenitor dividing cells, localized at the polar cortical region (PubMed:26766442). Detected in brain and liver (at protein level). Detected in brain, spleen, liver and testis, and at lower levels in heart, lung and kidney. Enriched in the ventricular zone of the developing central nervous systems (PubMed:12571286). Expressed in proximal colon, ileum, ovary, Sertoli cells of the testis and granular cells within the cerebellum (PubMed:31112734). Each GoLoco domain can bind one GNAI3 (PubMed:22952234). In the auto-inhibited conformation, the GoLoco domains interact with the TPR repeat region (PubMed:23665171). Belongs to the GPSM family. It is uncertain whether Met-1 or Met-8 is the initiator. Truncated N-terminus. Truncated N-terminus.