A unique phosphorylation-dependent mechanism for the activation of Ca2+/calmodulin-dependent protein kinase type IV/GR.
The activity of the Ca2+/calmodulin-dependent protein kinase IV/Gr (CaMKIV/Gr) is shown to be strictly regulated by phosphorylation of three residues both in vitro and in response to antigen receptor-mediated signaling in lymphocytes. One residue, Thr-200, is indispensable for enhancement of Ca2+/calmodulin-dependent basal activity by CaMKIV/Gr kinase. This event requires Ca2+/calmodulin in the full-length CaMKIV/Gr but is Ca2+/calmodulin-independent when a truncated version of CaMKIV/Gr is used as a substrate (DeltaCaMKIV/Gr1-317 (Delta1-317)). The other two residues, Ser12 and Ser13, are apparently autophosphorylated by the Ca2+/calmodulin-bound CaMKIV/Gr. Phosphorylation of neither Ser12-Ser13 nor Thr312 (the residue in a homologous position to Thr286 of CaMKIIalpha influences the development of Ca2+/calmodulin-independent activity or any other property of CaMKIV/Gr examined. Similarly, removal of the NH2-terminal 20 amino acids has no effect on the activation or function of CaMKIV/Gr. However, mutation of both Ser12 and Ser13 residues to Ala in Delta1-317 completely abrogates activity, while individual substitutions have no effect. These results indicate that the NH2-terminal Ser cluster mediates a novel type of intrasteric inhibition and suggest that three events are required for CaMKIV/Gr activation: 1) Ca2+/calmodulin binding; 2) phosphorylation of the Ca2+/calmodulin-bound enzyme on Thr200 by a Ca2+/calmodulin-dependent protein kinase kinase; and 3) autophosphorylation of Ser12-Ser13. This three-step requirement is unique among the multifunctional Ca2+/calmodulin-dependent kinases.
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- Tumor Cells, Cultured
- Recombinant Proteins
- Phosphorylation
- Mutagenesis, Site-Directed
- Humans
- Calcium-Calmodulin-Dependent Protein Kinases
- Calcium-Calmodulin-Dependent Protein Kinase Type 4
- Biochemistry & Molecular Biology
- 34 Chemical sciences
- 32 Biomedical and clinical sciences
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Tumor Cells, Cultured
- Recombinant Proteins
- Phosphorylation
- Mutagenesis, Site-Directed
- Humans
- Calcium-Calmodulin-Dependent Protein Kinases
- Calcium-Calmodulin-Dependent Protein Kinase Type 4
- Biochemistry & Molecular Biology
- 34 Chemical sciences
- 32 Biomedical and clinical sciences