Nuclear phosphoinositidase C during growth factor stimulation.
The existence of phosphoinositidase C beta is demonstrated in the nucleus of Swiss 3T3 cells. Moreover, we show that this isoform is specific for the nucleus while the gamma isoform is confined to the cytoplasm of these cells. When Swiss 3T3 fibroblasts are treated with Insulin-like Growth Factor I a rapid and transient activation of the beta isoform occurs at the nucleus whilst the cytoplasmic phosphoinositidase C is unaffected. These results seem to explain the mechanism by which the decrease in the mass of polyphosphoinositol lipids occurs in the nucleus after stimulation with Insulin-like Growth Factor I and actually point out the existence of a nuclear polyphosphoinositide signalling system distinct from the plasma membrane localized system and constituted not only by the previously demonstrated lipid kinases but also by a specific phosphoinositidase C.
Cocco
L
L
Institute of Human Anatomy, University of Bologna, Italy.
Martelli
A M
AM
Capitani
S
S
Maraldi
N M
NM
Mazzotti
G
G
Barnabei
O
O
Manzoli
F A
FA
D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000201:enzymology*; D003593:Cytoplasm / Q000201:enzymology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D051379:Mice; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*
D007334:Insulin-Like Growth Factor I; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase