Calcium fluxes cause nuclear shrinkage and the translocation of phospholipase C-delta1 into the nucleus.
Phospholipase C-delta1 (PLCdelta1) is the most fundamental form of the eukaryotic PLC and thought to play important roles in the regulation of cells. We previously reported that PLCdelta1 shuttles between the cytoplasm and nucleus, and an influx of Ca2+ triggers the nuclear import of PLCdelta1 via Ca2+-dependent interaction with importin beta1, although the physiological meaning of this is unclear. Here we have examined the distribution of PLCdelta1 using primary cultures of rat hippocampal neurons. Treatment of 7DIV neurons with ionomycin or thapsigargin caused the nuclear localization of PLCdelta1 as has been observed in other cell lines. Similar results were obtained with neurons treated with glutamate, suggesting that the nuclear localization of PLCdelta1 plays some roles in excitotoxicity associated with ischemic stress. Generally, cells undergoing ischemic or hypoxic cell death show nuclear shrinkage. We confirmed that a massive influx of Ca2+ caused similar results. Furthermore, overexpression of GFP-PLCdelta1 facilitated ionomycin-induced nuclear shrinkage in embryonic fibroblasts derived from PLCdelta1 gene-knockout mice (PLCdelta1KO-MEF). By contrast, an E341A mutant that cannot bind with importin beta1 and be imported into the nucleus by ionomycin and also lacks enzymatic activity did not cause nuclear shrinkage in PLCdelta1KO-MEF. Nuclear translocation and the PLC activity of PLCdelta1, therefore, may regulate the nuclear shape by controlling the nuclear scaffold during stress-induced cell death caused by high levels of Ca2+.
Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Hyogo 678-1297, Japan.
Masashi
M
Okada
Katsutoshi
K
Taguchi
Shohei
S
Maekawa
Kiyoko
K
Fukami
Hitoshi
H
Yagisawa
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D015687:Cell Hypoxia; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure*; D053144:Cell Nucleus Shape; D002478:Cells, Cultured; D005347:Fibroblasts / Q000201:enzymology; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D054803:Phospholipase C delta / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology
D007476:Ionophores; D018698:Glutamic Acid; D015759:Ionomycin; D019284:Thapsigargin; D054803:Phospholipase C delta; D000252:Calcium-Transporting ATPases; D002118:Calcium