Relationship between dopamine-stimulated phospholipid methylation and the single-carbon folate pathway.
In a previous study we demonstrated the ability of dopamine (DA) to stimulate phospholipid methylation (PLM) via a novel mechanism involving the D4 dopamine receptor (D4R) in which single-carbon folates appeared to be the primary source of methyl groups. To further understand the relationship between D4R-mediated PLM and folate metabolism, we examined the effect of several folate pathway interventions on the level of basal and DA-stimulated incorporation of [14C]-labeled formate into phospholipids in cultured SH-SY5Y neuroblastoma cells. These interventions included: (i) Overexpression of methenyltetrahydrofolate synthetase (MTHFS). (ii) Treatment with 5-formylTHF. (iii) Treatment with the MTHFS inhibitor 5-formyltetrahydrohomofolic acid (5-formylTHHF). (iv) Growth in nucleoside-free media. 31P-NMR was also used to follow DA-induced changes in cell phospholipid composition. MTHFS overexpression and 5-formylTHHF treatment, both of which lower 5-methylTHF levels, each reduced basal PLM and its stimulation by DA. In contrast, 5-formylTHF, which increases 5-methylTHF, caused a dose-dependent increase in both basal and DA-stimulated PLM. Growth in nucleoside-free media caused time-dependent changes in PLM, which were due to the absence of purine nucleosides. While basal PLM was maintained at a reduced level, DA-stimulated PLM was initially increased followed by a later decrease. Together, these findings indicate a close functional relationship between single-carbon folate metabolism and DA-stimulated PLM, consistent with a role for 5-methylTHF as the methyl donor for the D4R-mediated process.
Zhao
R
R
Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, USA.
Chen
Y
Y
Tan
W
W
Waly
M
M
Sharma
A
A
Stover
P
P
Rosowsky
A
A
Malewicz
B
B
Deth
R C
RC
D002250:Carbon Radioisotopes / Q000378:metabolism; D019731:Carbon-Nitrogen Ligases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008954:Models, Biological; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011684:Purine Nucleosides / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D050638:Receptors, Dopamine D4; D014407:Tumor Cells, Cultured
D002250:Carbon Radioisotopes; C493599:DRD4 protein, human; D004791:Enzyme Inhibitors; D010743:Phospholipids; D011684:Purine Nucleosides; D017448:Receptors, Dopamine D2; D050638:Receptors, Dopamine D4; D005492:Folic Acid; D019731:Carbon-Nitrogen Ligases; C021557:5,10-methenyltetrahydrofolate synthetase; D004298:Dopamine