PIP5K2A-dependent regulation of excitatory amino acid transporter EAAT3.
BACKGROUND
According to previous observations, the gene encoding the phosphatidylinositol-4-phosphate 5-kinase II alpha (PIP5K2A) is associated with schizophrenia. Specifically, the mutation (N251S)PIP5K2A has been discovered in schizophrenic patients but not in healthy individuals. A defect of the excitatory amino acid transporter EAAT3 has similarly been implicated in the development of schizophrenia. The present study thus explored whether PIP5K2A is involved in the regulation of EAAT3 activity.


METHODS
EAAT3 was expressed in Xenopus oocytes either without or with PIP5K2A, and EAAT3 transporter activity was estimated from the glutamate (2-mM)-induced current (I(glu)) in dual electrode voltage clamp experiments. EAAT3 protein abundance in the cell membrane was estimated by Western blotting and confocal microscopy.


RESULTS
In EAAT3-expressing oocytes, I(glu) was enhanced by coexpression of wild type PIP5K2A. Coexpression of the schizophrenia-associated mutant (N251S)PIP5K2A significantly decreased I(glu) in oocytes expressing EAAT3 with or without additional expression of wild type PIP5K2A. Thus, (N251S)PIP5K2A exerts a dominant inhibitory effect.


CONCLUSIONS
Membrane abundance of EAAT3 was increased by wild type PIP5K2A and decreased by (N251S)PIP5K2A in both EAAT3-expressing oocytes and human embryonic kidney cells. The present observations disclose a novel mechanism of EAAT3 regulation, which may contribute to the deranged regulation of excitability in schizophrenic patients.
Fedorenko
Olga
O
Department of Physiology, University of Tuebingen, Gmelinstr. 5, 72076 Tuebingen, Germany.
Tang
Cai
C
Sopjani
Mentor
M
Föller
Michael
M
Gehring
Eva-Maria
EM
Strutz-Seebohm
Nathalie
N
Ureche
Oana N
ON
Ivanova
Svetlana
S
Semke
Arkadij
A
Lang
Florian
F
Seebohm
Guiscard
G
Lang
Undine E
UE
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D050580:Excitatory Amino Acid Transporter 3 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D018613:Microscopy, Confocal; D009154:Mutation; D009865:Oocytes; D018408:Patch-Clamp Techniques; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D012559:Schizophrenia / Q000235:genetics; D014981:Xenopus
D050580:Excitatory Amino Acid Transporter 3; C493400:SLC1A1 protein, human; D018698:Glutamic Acid; C514871:PIP4K2A protein, human; D017853:Phosphotransferases (Alcohol Group Acceptor)