This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ekanger, R. Articles by Døskeland, S. O. Search for Related Content PubMed PubMed Citation Articles by Ekanger, R. Articles by Døskeland, S. O.

Characterization of Cyclic Adenosine 3':5'-Monophosphate-dependent Protein Kinase Isozymes in Normal and Neoplastic Fetal Rat Brain Cells¹

Cell Biology Research Group, Institute of Anatomy, University of Bergen, årstadveien 19, N-5000 Bergen [R. E., D. Ø., O. E., O. V., S. O. D.], and Department of Pathology, The Gade Institute, University of Bergen, Haukeland Hospital, N-5016 Bergen [O. D. L.], Norway

Fetal brain cells from rats given a transplacental pulse of N-ethyl-N-nitrosourea progressively acquire malignant characteristics and dedifferentiate when grown in vitro. One aspect of this dedifferentiation is a decreased morphological response to cyclic adenosine 3':5'-monophosphate (cAMP). In the present study, we have characterized and compared the isozymes (I, II) of cAMP-dependent protein kinase in fetal brain cells and in the neoplastically transformed, dedifferentiated BT5C glioma cell line. This is a first approach to find the mechanism behind the subresponsiveness of such cells towards cAMP. It is also part of a broader investigation of the cAMP effector system in cells showing various rates of normal and malignant growth.

We found the regulatory and catalytic subunits of cAMP-dependent protein kinase to be expressed to a similar degree in both cell types. Sixty % of the enzyme was located in the 30,000 x g supernatant. The glioma cell line had a significantly higher ratio (1.2) between protein kinase I and II than did the normal fetal cells (0.5). This difference in isozyme distribution was not apparent using conventional methods for enzyme separation and detection, the use of specific antibodies being essential for that purpose. Of the chromatographically separated forms (a, b) of protein kinase II, Form IIa was selectively decreased in the glioma cell line.

The alterations of the protein kinases in the glioma cell line described above may be of importance for some of the neoplastic properties of these cells. However, the subdued response of such cells towards cAMP is not explained since the concentrations of cAMP or its analogues required for activation of the kinases were similar for the enzymes from normal and neoplastically transformed cells.

¹ This work was supported by the Norwegian Cancer Society (LMK).

² To whom requests for reprints should be addressed.

Received 11/27/85. Revised 2/13/85. Accepted 2/15/85.