Involved in an inositol phospholipid-based intracellular signaling cascade. Shows no PLC activity to phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol. Component in the phospho-dependent endocytosis process of GABA A receptor (By similarity). Regulates the turnover of receptors and thus contributes to the maintenance of GABA-mediated synaptic inhibition. Its aberrant expression could contribute to the genesis and progression of lung carcinoma. Acts as an inhibitor of PPP1C. Interacts with PPP2CA (By similarity). Interacts with Ins(1,4,5)P3, Ins(1,4,5,6)P4, GABARAP, GABA receptor beta subunits, GABA receptor gamma-2 subunits and PPP1C. May form a ternary complex with GABA receptor beta subunit and GABARAP. The formation of a ternary complex with GABA receptor beta subunit and GABARAP could be the key step for facilitating the association of GABARAP with the GABA receptor gamma-2 subunit and to allow it to be transported at the right destination. Expressed in a variety of fetal and adult organs including brain, lung and kidney. Its expression was greatly reduced in small and non-small cell lung carcinoma. Isoform 1 is predominantly expressed in brain. Phosphorylated by the catalytic subunit of PKA. Phosphorylation of Thr-93 resulted in dissociation of PPP1C from PRIP1 (By similarity). In the PI-PLC X-box Asn-458 is present instead of the conserved His which is one of the active site residues. It is therefore expected that this protein lacks catalytic activity.