Induction of filopodia-like protrusions in N1E-115 neuroblastoma cells by diacylglycerol kinase γ independent of its enzymatic activity: potential novel function of the C-terminal region containing the catalytic domain of diacylglycerol kinase γ.
Type I diacylglycerol kinase (DGK) isozymes (α, β, and γ) contain recoverin homology domains and calcium-binding EF-hand motifs at their N-termini. The γ-isoform of DGK is abundantly expressed in retinal and Purkinje cells; however, its function in neuronal cells remains unknown. Here, we report that the mRNA and protein levels of DGKγ, but not DGKα or β, were markedly increased in N1E-115 neuroblastoma cells upon cellular differentiation by serum starvation. Interestingly, overexpression of wild-type DGKγ, which was partially located at the plasma membrane, considerably induced the formation of slender, filopodia-like cytoplasmic projections from N1E-115 cell bodies. Deletion of the recoverin homology domain and the EF-hand motifs, which potentiated the plasma membrane localization of the isozyme, significantly enhanced the formation of the filopodia-like protrusions. Intriguingly, the catalytic activity of the isozyme is not essential for the protrusion formation. The N-terminal half of the catalytic domain and a short stretch of amino acid residues at the C-terminus are responsible for plasma membrane localization and filopodia-like process formation. Taken together, we have described a potentially novel morphological function of the C-terminal DGKγ catalytic region that is independent of its enzymatic activity.
Department of Chemistry, Graduate School of Science Chiba University, 1-33 Yayoi-cho, Chiba 263-8522, Japan.
Fumihiko
F
Tanino
Yuki
Y
Maeda
Hiromichi
H
Sakai
Fumio
F
Sakane
D000818:Animals; D020134:Catalytic Domain; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D016895:Culture Media, Serum-Free; D019852:Diacylglycerol Kinase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015870:Gene Expression; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D009447:Neuroblastoma; D021381:Protein Transport; D011554:Pseudopodia / Q000201:enzymology*; D017384:Sequence Deletion
D016895:Culture Media, Serum-Free; D007527:Isoenzymes; D019852:Diacylglycerol Kinase