DDHD Domain Containing Protein 1 (DDHD1)

 DDHD1, previously identified as phosphatidic acid (PA)-preferring PLA1 (PA-PLA1), is involved in the formation of 2-arachidonoyl-LPI. DDHD1 was translocated from the cytosol to membranes upon ionomycin treatment. DDHD1 binds PA, and the addition of PA to DDHD1 increased the affinity for PI (K(m) ; 3 mol%) and augmented the PI-PLA1 activity. DDHD1 activated by PA was returned to a basal state by its own PA-hydrolytic activity. These results implicate DDHD1 in the formation of 2-arachidonoyl-LPI and indicate that the process is modulated by PA released by phospholipase D. Similar observations for the production of arachidonic acid-containing LPI in neuroblastoma cells suggest the DDHD1-LPI-GPR55 axis to be involved in functions in the brain.