Essential role of neuron-enriched diacylglycerol kinase (DGK), DGKbeta in neurite spine formation, contributing to cognitive function.
BACKGROUND
Diacylglycerol (DG) kinase (DGK) phosphorylates DG to produce phosphatidic acid (PA). Of the 10 subtypes of mammalian DGKs, DGKbeta is a membrane-localized subtype and abundantly expressed in the cerebral cortex, hippocampus, and caudate-putamen. However, its physiological roles in neurons and higher brain function have not been elucidated.


RESULTS
We, therefore, developed DGKbeta KO mice using the Sleeping Beauty transposon system, and found that its long-term potentiation in the hippocampal CA1 region was reduced, causing impairment of cognitive functions including spatial and long-term memories in Y-maze and Morris water-maze tests. The primary cultured hippocampal neurons from KO mice had less branches and spines compared to the wild type. This morphological impairment was rescued by overexpression of DGKbeta. In addition, overexpression of DGKbeta in SH-SY5Y cells or primary cultured mouse hippocampal neurons resulted in branch- and spine-formation, while a splice variant form of DGKbeta, which has kinase activity but loses membrane localization, did not induce branches and spines. In the cells overexpressing DGKbeta but not the splice variant form, DGK product, PA, was increased and the substrate, DG, was decreased on the plasma membrane. Importantly, lower spine density and abnormality of PA and DG contents in the CA1 region of the KO mice were confirmed.


CONCLUSIONS
These results demonstrate that membrane-localized DGKbeta regulates spine formation by regulation of lipids, contributing to the maintenance of neural networks in synaptic transmission of cognitive processes including memory.
Shirai
Yasuhito
Y
Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe, Japan.
Kouzuki
Takeshi
T
Kakefuda
Kenichi
K
Moriguchi
Shigeki
S
Oyagi
Atsushi
A
Horie
Kyoji
K
Morita
Shin-ya
SY
Shimazawa
Masamitsu
M
Fukunaga
Kohji
K
Takeda
Junji
J
Saito
Naoaki
N
Hara
Hideaki
H
D000818:Animals; D015139:Blotting, Southern; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003071:Cognition / Q000502:physiology*; D019852:Diacylglycerol Kinase / Q000235:genetics / Q000378:metabolism*; D004594:Electrophysiology; D005260:Female; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D016501:Neurites / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction
D019852:Diacylglycerol Kinase