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Nuclear substrates of protein kinase C
R Beckmann1, K Buchner, P R Jungblut
1Institut für Biochemie, Freie Universität Berlin, Federal Republic of Germany.
European Journal of Biochemistry
|November 15, 1992
Summary
Researchers identified nuclear protein B23 as a substrate for protein kinase C (PKC) in neuronal cells. This finding advances understanding of nuclear signaling pathways and protein regulation within the cell nucleus.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Nuclear-membrane-associated protein kinase C (PKC) exists in a constitutively active, membrane-inserted form in neuronal cells.
- Identifying substrates of this nuclear PKC is crucial for understanding its regulatory functions.
Purpose of the Study:
- To identify specific substrates phosphorylated by the constitutively active nuclear PKC in neuronal cells.
- To elucidate the role of nuclear PKC in regulating nuclear protein function.
Main Methods:
- Preparation of nuclear membranes and subcellular fractions from bovine brain.
- In-vitro phosphorylation assays using nuclear fractions and purified PKC.
- Proteomic analysis including 2D gel electrophoresis, in-situ digestion, HPLC, and microsequencing.
Main Results:
- Several nuclear membrane proteins were phosphorylated by nuclear PKC, with activity inhibited by specific PKC inhibitors.
- Two nuclear PKC substrates were identified: Lamin B2 (control) and nucleolar protein B23.
- Phosphorylation of nucleolar protein B23 by PKC was specifically mapped to Serine 225.
Conclusions:
- Nucleolar protein B23 is a novel substrate for nuclear protein kinase C (PKC) in neuronal cells.
- Serine 225 of protein B23 is a key site for PKC-mediated phosphorylation.
- These findings highlight a role for nuclear PKC in regulating nucleolar protein function and cellular signaling.