Selective Distribution of Protein Kinase A Regulatory Subunit RIIAlpha in Rodent Gliomas

¹ Department of Human Anatomy and Physiology, University of Padova, Italy
² Department of Biomedical and Morphological Sciences, Section of Anatomy and Histology, University of Verona, Italy

^* To whom correspondence should be addressed. E-mail: carla.mucignat{at}unipd.it.

	Abstract

Differential diagnosis of brain tumor types is mainly based on cell morphology, and could benefit from additional markers. The cAMP second messenger system is involved in regulating cell proliferation and differentiation and is conceivably modulated during cancer transformation. It mainly activates protein kinases, that are in part docked to cytoskeleton, membranes or organelles by anchoring proteins, forming protein aggregates that are detergent-insoluble and not freely diffusible, and are characteristics for each cell type.

The intracellular distribution of the detergent-insoluble regulatory subunits (R) of the cAMP dependent protein kinase has been examined in mouse and rat glioma cells both in vitro and in vivo by immunohistochemistry. In normal rodent brains, the RII regulatory subunit is detergent-insoluble only in ependymal cells, while in the rest of brain it is present in soluble form. Immunohistochemistry shows that in both mouse and rat glioma cell lines RII is mainly detergent-insoluble. It is localized close to the nucleus, associated to smooth vesicles in the trans-Golgi network area. Both paclitaxel and vinblastine cause a redistribution of RII within the cell. Under conditions that increased intracellular cAMP, apoptosis of glioma cells was observed, and was accompanied by RII redistribution. Also in vivo, detergent-insoluble RII can be observed in mouse and rat gliomas, where it delineates the border between normal brain tissue and glioma. Therefore, intracellular distribution of detergent-insoluble RII can assist in detecting tumor cells within the brain, thus making the histologic diagnosis of brain tumors more accurate, and may represent an additional target for therapy.

Key Words: Glioblastoma, cAMP, protein kinase A, diagnosis, Golgi

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