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Uptake and phosphorylation of phosphatidylinositol by rat liver nuclei. Role of phosphatidylinositol transfer protein

1990; Elsevier BV; Volume: 1044; Issue: 2 Linguagem: Inglês

10.1016/0005-2760(90)90303-f

1879-145X

Silvano Capitani, Bernd Helms, Meri Mazzoni, Maurizio Previati, Valeria Bertagnolo, K.W.A. Wirtz, Francesco A. Manzoli,

Diet, Metabolism, and Disease

The incorporation of phosphatidyl[2-3H]inositol ([3H]PI) from vesicles or microsomal membranes into rat liver nuclei is greatly stimulated by phosphatidylinositol transfer protein (PI-TP). The nuclei are able to phosphorylate [3H]PI, with the production of phosphatidylinositol 4-phosphate (PIP). Recovery of tritiated inositol trisphosphate, inositol phosphate, glycerophosphoinositol and inositol, suggests that in isolated nuclei a large set of enzymes of the PI cycle is present, similar to the enzymes involved in the plasma membrane PI cycle. Incubation with [gamma-32P]ATP shows that isolated nuclei are able to phosphorylate endogenous PI to PIP and phosphatidylinositol 4,5-bisphosphate (PIP2). In the presence of exogenous PI and detergent the synthesis of PIP is increased, indicating that in nuclei the PI pool is suboptimal for the PI-kinase activity. The present study suggests that PI-TP may be involved in providing substrates for PI metabolism at the nuclear level.