Activation of phosphoinositide 3-kinase C2 beta in the nuclear matrix during compensatory liver growth.
In the nuclear matrix harvested 20 h after partial hepatectomy, an increase in immunoprecipitable PI3K-C2beta activity is observed, which is sensitive to wortmannin (10 Mm) and shows strong preference for PtdIns over PtdIns(4)P as a substrate. On western blots PI3K-C2beta revealed a single immunoreactive band of 180 kD, whereas 20 h after partial hepatectomy gel shift of 18kDa was noticed in the nuclear matrix, suggesting that observed activation of enzyme is achieved by proteolysis. As it is know that PI3K-C2alpha is associated with nuclear speckles [Didichenko SA, Thelen M. Phosphatidylinositol 3-kinase C2alpha contains a nuclear localization sequence and associates with nuclear speckles. J Biol Chem 2001;276:48135-42.], the data presented in this report show that in the nuclear matrix PI3K-C2beta is activated during the compensatory liver growth, which clearly demonstrates that different class II PI3K enzymes have different subnuclear localization and therefore might have different intranuclear functions.
Sindić
Aleksandra
A
Department of Physiology and Croatian Institute for Brain Research, School of Medicine, University of Zagreb, P.O. Box 978, Salata 3, 10 001 Zagreb, Croatia.
Crljen
Vladiana
V
Matković
Katarina
K
Lukinović-Skudar
Vesna
V
Visnjić
Dora
D
Banfić
Hrvoje
H
D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D004789:Enzyme Activation / Q000502:physiology; D008099:Liver / Q000201:enzymology* / Q000254:growth & development*; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D021122:Protein Subunits; D019869:Phosphatidylinositol 3-Kinases; C516123:Pik3c2b protein, rat