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Calmodulin-dependent protein kinases in rat glioblastoma
Abstract:
The mitogenic activity of several growth factors is mediated by calcium-dependent signal transduction. Calmodulin (CaM) binding proteins such as CaM-dependent protein kinases are important components of this pathway and may be altered in diseases characterized by abnormal cell growth. CaM kinase II is believed to regulate the phosphorylation of microtubular-associated proteins and control the initiation of DNA synthesis. Furthermore, drugs that inhibit CaM-mediated signal transduction also inhibit cellular proliferation and are cytotoxic to numerous malignant cell lines, including those established from malignant gliomas. Yet, little is known about CaM-dependent protein kinases in these tumors. Therefore, we have investigated the activity and distribution of CaM-dependent protein kinase II in normal and malignant glial tissues, a kinase believed to play a critical role in cell cycle regulation. C6 and 9L cells contained kinase activities that were activated by Ca2+/CaM and inhibited by trifluoperazine. Tissue extracts from these cell lines and from rat brain white matter phosphorylated exogenous synapsin I in a pattern consistent with the presence of CaM kinase II activity as determined by phosphopeptide mapping. CaM kinase II activity was confirmed using a specific peptide substrate and inhibitor. An unexpected finding was that glioma lines, but not rat brain white matter, also contained a CaM-dependent protein kinase detected by the phosphorylation of a M(r) 100,000 protein, subsequently identified as elongation factor 2, the only known substrate for CaM kinase III.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
This study investigated calmodulin-dependent protein kinase II (CaM kinase II) in gliomas, finding its activity in malignant cells and normal brain tissue. Unexpectedly, glioma cells also showed CaM kinase III activity, suggesting roles in cell cycle regulation.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Calcium-dependent signal transduction pathways, involving calmodulin (CaM) binding proteins, regulate cell growth.
- CaM-dependent protein kinases, particularly CaM kinase II, are implicated in cell cycle regulation and DNA synthesis.
- Abnormalities in these pathways are linked to diseases with uncontrolled cell proliferation, such as malignant gliomas.
Purpose of the Study:
- To investigate the activity and distribution of CaM-dependent protein kinase II in normal and malignant glial tissues.
- To explore the role of CaM-dependent protein kinases in the cell cycle regulation of gliomas.
Main Methods:
- Assessed CaM-dependent protein kinase activity in C6 and 9L glioma cell lines and rat brain white matter.
- Utilized Ca2+/CaM activation and trifluoperazine inhibition assays.
- Employed phosphopeptide mapping and specific peptide substrates/inhibitors to confirm CaM kinase II activity.
- Investigated phosphorylation of a M(r) 100,000 protein in glioma lines.
Main Results:
- CaM kinase II activity was detected in both glioma cell lines and rat brain white matter.
- Kinase activity in these tissues was activated by Ca2+/CaM and inhibited by trifluoperazine.
- Glioma cell lines, but not normal brain white matter, exhibited CaM-dependent phosphorylation of a M(r) 100,000 protein, identified as elongation factor 2 (a CaM kinase III substrate).
Conclusions:
- CaM kinase II is present and active in both normal glial tissue and malignant gliomas.
- Glioma cells possess an additional CaM-dependent kinase activity, likely CaM kinase III, targeting elongation factor 2.
- These findings highlight the potential involvement of CaM-dependent kinases in glioma pathogenesis and cell cycle regulation.