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Protein kinase C delta (PKC delta): activation mechanisms and functions
Ushio Kikkawa1, Hidenori Matsuzaki, Toshiyoshi Yamamoto
1Biosignal Research Center, Kobe University, Kobe 657-8501, Japan. ukikkawa@kobe-u.ac.jp
Abstract:
Protein kinase C (PKC)delta was the first new/novel PKC isoform to be identified by the screening of mammalian cDNA libraries, based on the structural homology of its nucleotide sequences with those of classical/conventional PKC isoforms. PKC delta is expressed ubiquitously among cells and tissues. It is activated by diacylglycerol produced by receptor-mediated hydrolysis of membrane inositol phospholipids as well as by tumor-promoting phorbol ester through the binding of these compounds to the C1 region in its regulatory domain. It is also cleaved by caspase to generate a catalytically active fragment, and it is converted to an active form without proteolysis through the tyrosine phosphorylation reaction. Various lines of evidence indicate that PKC delta activated in distinct ways plays critical roles in cellular functions such as the control of growth, differentiation, and apoptosis. This article briefly summarizes the regulatory mechanisms of PKC delta activity and its functions in cell signaling.
Insights
Protein kinase C delta (PKC delta) is a key signaling molecule activated through various mechanisms, including proteolysis and phosphorylation. It plays vital roles in cell growth, differentiation, and apoptosis.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Protein kinase C delta (PKC delta) is a novel isoform identified through cDNA library screening.
- It exhibits ubiquitous expression across various cells and tissues.
- PKC delta shares structural homology with classical/conventional PKC isoforms.
Purpose of the Study:
- To summarize the regulatory mechanisms of PKC delta activity.
- To elucidate the functions of PKC delta in cell signaling pathways.
- To highlight the distinct activation pathways of PKC delta.
Main Methods:
- Analysis of cDNA libraries for novel PKC isoforms.
- Investigation of activation mechanisms including diacylglycerol binding to the C1 region.
- Examination of caspase-mediated cleavage and tyrosine phosphorylation for activation.
- Review of existing literature on PKC delta's role in cellular processes.
Main Results:
- PKC delta is activated by diacylglycerol and phorbol esters via its C1 regulatory domain.
- Proteolytic cleavage by caspases generates an active fragment.
- Tyrosine phosphorylation can also convert PKC delta to an active form without cleavage.
- Activated PKC delta is implicated in controlling cell growth, differentiation, and apoptosis.
Conclusions:
- PKC delta is a versatile signaling enzyme with multiple activation pathways.
- Its activation is crucial for regulating fundamental cellular functions.
- Understanding PKC delta regulation is key to deciphering complex cell signaling networks.