Generation of lysophosphatidylinositol by DDHD domain containing 1 (DDHD1): Possible involvement of phospholipase D/phosphatidic acid in the activation of DDHD1.
GPR55 is a seven-transmembrane G-protein-coupled receptor that has been proposed as a novel type of cannabinoid receptor. Previously, we identified lysophosphatidylinositol (LPI), in particular 2-arachidonoyl-LPI, as an agonist for GPR55. In the present study, we examined whether intracellular phospholipase A1 (DDHD domain containing 1, or DDHD1), previously identified as phosphatidic acid (PA)-preferring PLA1 (PA-PLA1), is involved in the formation of 2-arachidonoyl-LPI. HEK293 cells expressing DDHD1 produced [(3)H]arachidonic acid-containing LPI after prelabeling with [(3)H]arachidonic acid and subsequent activation by ionomycin; the formation of [(3)H]LPI was inhibited by n-butanol and the overexpression of an inactive PLD1 mutant PLD1K898R. DDHD1 was translocated from the cytosol to membranes upon ionomycin treatment. A purified recombinant DDHD1 formed [(3)H]LPI when incubated with [(3)H]PI; the V(max) and apparent K(m) were 190 micromol/min/mg protein and 10 mol% PI, respectively. 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.
Yamashita
Atsushi
A
Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Sagamihara, Kanagawa 229-0195, Japan. ayamashi@pharm.teikyo-u.ac.jp
Kumazawa
Tsukasa
T
Koga
Hiroki
H
Suzuki
Naotaka
N
Oka
Saori
S
Sugiura
Takayuki
T
D001921:Brain / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008246:Lysophospholipids / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D010712:Phosphatidic Acids / Q000235:genetics / Q000378:metabolism*; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
C524885:GPR55 protein, human; D007476:Ionophores; D008246:Lysophospholipids; D010712:Phosphatidic Acids; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled; D011994:Recombinant Proteins; C025449:lysophosphatidylinositol; D015759:Ionomycin; D010739:Phospholipase D