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Phosphorylation of microtubule-associated proteins by protein kinase CK2 in neuritogenesis
1Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Spain.
Abstract:
Phosphorylation of microtubule-associated protein MAP1B and the neuronal-specific beta III-tubulin isoform takes place during neurite growth in neuroblastoma cells. Protein kinase CK2 (formerly referred to as casein kinase 2) is possibly involved in beta III-tubulin phosphorylation. As for MAP1B, there are at least two types of phosphorylation; one catalyzed by proline-directed protein kinases and another catalyzed by CK2. Protein kinase CK2 is primarily localized to the nuclei in proliferating neuroblastoma cells, whereas an increased amount of the enzyme is present in the cytoplasm of postmitotic cells bearing neurites. Treatment of neuroblastoma cells with an antisense oligonucleotide which specifically results in CK2 catalytic subunit depletion inhibits neuritogenesis. CK2 depletion is accompanied by dephosphorylation of MAP1B on the corresponding phosphorylatable sites. This dephosphorylation is paralleled by a release of MAP1B from microtubules. These results suggest that MAP1B phosphorylation by CK2 may be required for the assembly of microtubules within neurites. Other neuronal cytoskeletal proteins including MAP1A and tau are also substrates for CK2, indicating a role for the enzyme in the regulation of cytoskeletal functions also in mature neurons.
Insights
Protein kinase CK2 (casein kinase 2) is crucial for neurite growth by phosphorylating microtubule-associated protein MAP1B. Depleting CK2 inhibits neuritogenesis and MAP1B assembly into microtubules.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Neurite growth involves phosphorylation of microtubule-associated protein MAP1B and beta III-tubulin.
- Protein kinase CK2 (casein kinase 2) is implicated in beta III-tubulin phosphorylation.
- MAP1B undergoes phosphorylation by proline-directed kinases and CK2.
Purpose of the Study:
- To investigate the role of protein kinase CK2 in neurite growth and MAP1B phosphorylation.
- To determine the localization and function of CK2 during neuroblastoma cell differentiation.
Main Methods:
- Using antisense oligonucleotides to deplete CK2 catalytic subunit in neuroblastoma cells.
- Analyzing MAP1B phosphorylation status and its association with microtubules.
- Observing effects on neuritogenesis and cytoskeletal organization.
Main Results:
- CK2 depletion inhibited neuritogenesis and caused MAP1B dephosphorylation.
- Dephosphorylated MAP1B was released from microtubules.
- CK2 localization shifted from nucleus to cytoplasm during neurite outgrowth.
Conclusions:
- CK2-mediated MAP1B phosphorylation is essential for microtubule assembly during neurite extension.
- CK2 plays a significant role in regulating neuronal cytoskeletal dynamics.
- CK2 may regulate other neuronal cytoskeletal proteins like MAP1A and tau.