Immunocytochemical localization of a neuron-specific diacylglycerol kinase β and γ in the developing rat brain

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA) and is, therefore, a potential terminator of DG signaling. DG and PA are important intracellular second messengers. DG directly binds protein kinase C (PKC) then activates this multifunctional enzyme. Ca²⁺-dependent and brain-specific DGKs, α, β, and γ, are suggested to play pivotal roles in the central nervous system. To elucidate the DGK function in neuronal development, we studied the developmental changes of DGKα, β, and γ in the postnatal rat brain. By immunoblot analysis, DGKα and γ subtypes were present at birth and then gradually increased, while DGKβ was not present at birth or postnatal day 3, then increased rapidly from day 14 to reach maximum at day 28. Immunohistochemically, DGKβ and γ were distributed in different brain regions. In most brain regions, DGKγ showed sustained expression throughout the postnatal developmental periods. Interestingly, a temporal expression of DGKγ was observed in the medial geniculate nucleus during day 3 to 14, and a delay of DGKγ expression was seen in Purkinje cells, which was coincident with dendritic growth of Purkinje cells. In the hippocampal pyramidal cell, both DGKβ and γ were abundant but subcellular localization was different. DGKγ localized in the cytosol while DGKβ localized along the membrane structure. These findings suggest that each DGK subtype has a spatio-temporally different function in the developmental neurons.