Phosphoinositide signalling enzymes in rat liver nuclei: phosphoinositidase C isoform beta 1 is specifically, but not predominantly, located in the nucleus.
The presence of phosphoinositide-mobilizing enzymes has been investigated in purified rat liver nuclei by radiolabelling and by probing with antibodies. A Ca(2+)-activated phosphoinositidase C (PIC) is present and was shown immunologically to be the beta 1 isoform. No gamma- or delta-PIC was found. However, only 5% of the total beta 1-PIC isoform is nuclear, with the majority being cytosolic. G alpha q and G alpha 11, the suggested physiological activators of beta 1-PIC, were not present. A PtdIns4P 5-kinase is also present, which immunologically is shown to be the C isoform. All of these nuclear inositide enzymes still remained after the removal of the nuclear envelope with Triton X-100, consistent with the concept of an intranuclear inositide cycle [Divecha, Banfic and Irvine (1991) EMBO. J. 10, 3207-3214].
Department of Biochemistry, AFRC Institute of Animal Physiology and Genetics Research, Cambridge, U.K.
N
N
Divecha
S G
SG
Rhee
A J
AJ
Letcher
R F
RF
Irvine
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D007527:Isoenzymes / Q000032:analysis* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008297:Male; D009685:Nuclear Envelope; D010716:Phosphatidylinositols / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000032:analysis* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000201:enzymology
D007527:Isoenzymes; D010716:Phosphatidylinositols; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D002118:Calcium