Histochemistry and Cell Biology

, Volume 106, Issue 5, pp 457–464 | Cite as

Cytoplasmic and nuclear localization sites of phosphatidylinositol 3-kinase in human osteosarcoma sensitive and multidrug-resistant Saos-2 cells

  • Nicoletta Zini
  • Andrea Ognibene
  • Alberto Bavelloni
  • Spartaco Santi
  • Patrizia Sabatelli
  • Nicola Baldini
  • Katia Scotlandi
  • Massimo Serra
  • Nadir Mario Maraldi
Original Paper


The intracellular localization of phosphatidylinositol 3-kinase (PI 3-kinase) has been analyzed by western blotting, confocal, and electron microscopy immunocytochemistry in human osteosarcoma Saos-2 cells. By western blotting, the enzyme appears to be present in both the cytoplasmic and nuclear subfractions. By confocal microscope immunocytochemistry, the cytoplasmic fluorescence is localized in the perinuclear region and on a network of filaments, while a diffused signal is present in the nucleus, except for the nucleolar areas. Ultrastructural analyses on whole cells and on in situ matrix preparations reveal that nuclear PI 3-kinase is localized in interchromatin domains, in stable association with inner nuclear matrix components, while the enzyme diffused in the cytosol is partly associated with the cytoskeletal filaments. Quantitative evaluations indicate that, in a multidrug-resistant variant obtained by continuous exposure of Saos-2 cells to doxorubicin, the amount of nuclear and cytoplasmic PI 3-kinase is significantly lower than in the sensitive parental cell line. The nuclear localization of PI 3-kinase and its variation in multidrug-resistant cells, characterized by a reduced mitotic index, are consistent with the data on the existence of a nuclear inositol lipid cycle, which could also utilize 3-phosphorylated inositides to modulate signal transduction for the control of some key functional activities.


Nerve Growth Factor Nuclear Matrix Cytoskeletal Filament Matrix Preparation Sensitive Parental Cell Line 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Nicoletta Zini
    • 1
  • Andrea Ognibene
    • 2
  • Alberto Bavelloni
    • 2
  • Spartaco Santi
    • 1
  • Patrizia Sabatelli
    • 1
  • Nicola Baldini
    • 3
  • Katia Scotlandi
    • 3
  • Massimo Serra
    • 3
  • Nadir Mario Maraldi
    • 1
  1. 1.Istituto di Citomorfologia Normale e Patologica C.N.R. Chieti-Bologna, c/o IORBolognaItaly
  2. 2.Laboratorio di Biologia Cellulare e Microscopia ElettronicaIOR, via di Barbiano 1/10BolognaItaly
  3. 3.Dipartimento di OncologiaIORBolognaItaly

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