Acts as a regulator of G protein signaling (RGS). Modulates G protein alpha subunits nucleotide exchange and hydrolysis activities by functioning either as a GTPase-activating protein (GAP), thereby driving G protein alpha subunits into their inactive GDP-bound form, or as a GDP-dissociation inhibitor (GDI). Confers GDI and GAP activities on G(i) alpha subunit Galphai. Confers GAP activity on G(o)-alpha subunit Galphao and G(i) alpha subunit Galphai. Involved in the dorsal-ventral axis formation of the egg. Acts as a G-protein signaling for glial cell differentiation during embryogenesis; Galphai, Galphao and the G-protein coupled receptor, moody, are required in the surface glia to achieve effective insulation of the nerve cord. May be essential for nurse cell dumping during oogenesis. Required in neuroblast asymmetrical cell division. Plays a role in stress resistance and life span control. Interacts (via GoLoco and RGS domains) with Galphai (via GDP- or GTP-bound forms). Recruited from the cytosol to the plasma membrane by the G(i) alpha subunit. Colocalizes with moody at the plasma membrane. Localizes as a crescent to the apical cortex in interphase and forms an apical crescent and segregates into the apical daughter cell at telophase. Colocalizes with Galphai and raps/pins at the apical cortex throughout mitosis. Expressed in surface and longitudinal glial cells, gut and heart (at protein level). Expressed both maternally and zygotically. Expressed during oogenesis and embryogenesis. Isoform 3 and isoform 4 are expressed in the germarium at stage 2. Isoform 4 is expressed in the nurse cells at stage 6 until the nurse cells degenerate. Isoform 3 is expressed in the follicle cells at stage 8, in the anterior-dorsal follicles cells from stage 10 until the follicles degenerate. Isoform 2 and isoform 3 are expressed in late stage 12 embryos, onwards. Isoform 2 is expressed in tracheal cells and in lateral glial cells within the CNS in late stage 16 embryos. Homozygous mutant flies show dorsal-ventral defects in egg (shorter egg length and fused appendages) and embryo patterning. Fail to hatch and show severe glial cell differentiation defects: disruption of intimate glial-glial cell contact and absence of glial cell processes enwrapping neuronal cell bodies and axones, resulting in loss of the blood-brain barrier (BBB) formation. Heterozygous flies show an enhanced stress resistance, fat content and extended lifespan.