Altered expression of diacylglycerol kinase isozymes in regenerating liver.
The liver possesses the capacity to restore its function and mass after injury. Liver regeneration is controlled through complicated mechanisms, in which the phosphoinositide (PI) cycle is shown to be activated in hepatocytes. Using a rat partial hepatectomy (PH) model, the authors investigated the expression of the diacylglycerol kinase (DGK) family, a key enzyme in the PI cycle, which metabolizes a lipid second-messenger diacylglycerol (DG). RT-PCR analysis shows that DGKζ and DGKα are the major isozymes in the liver. Results showed that in the process of regeneration, the DGKζ protein, which is detected in the nucleus of a small population of hepatocytes in normal liver, is significantly increased in almost all hepatocytes. However, the mRNA levels remain largely unchanged. Double labeling with bromodeoxyuridine (BrdU), an S phase marker, reveals that DGKζ is expressed independently of DNA synthesis or cell proliferation. However, DGKα protein localizes to the cytoplasm in normal and regenerating livers, but immunoblot analysis reveals that the expected (80 kDa) and the lower (70 kDa) bands are detected in normal liver, whereas at day 10 after PH, the expected band is solely recognized, showing a different processing pattern of DGKα in liver regeneration. These results suggest that DGKζ and DGKα are involved, respectively, in the nucleus and the cytoplasm of hepatocytes in regenerating liver.
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Tomoyuki
T
Nakano
Yasukazu
Y
Hozumi
Kiyoshi
K
Iwazaki
Kazuo
K
Okumoto
Ken
K
Iseki
Takafumi
T
Saito
Sumio
S
Kawata
Ichiro
I
Wakabayashi
Kaoru
K
Goto
D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D019852:Diacylglycerol Kinase / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D006498:Hepatectomy; D022781:Hepatocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008115:Liver Regeneration / Q000235:genetics*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
D007527:Isoenzymes; D004247:DNA; D019852:Diacylglycerol Kinase