A continuous fluorescence assay for protein kinase C

Area of Science:

• Biochemistry
• Molecular Biology
• Enzyme Assays

Background:

• Protein kinase C (PKC) plays a crucial role in cellular signaling pathways.
• Accurate quantification of PKC activity is essential for understanding its biological functions and associated diseases.
• Existing methods for measuring PKC activity can be complex or lack sensitivity.

Purpose of the Study:

• To develop a novel, continuous fluorescence-based assay for quantifying protein kinase C (PKC) activity.
• To characterize the sensitivity and specificity of this new assay.
• To demonstrate the utility of the assay in both purified systems and crude biological homogenates.

Main Methods:

• A 6-acryloyl-2-dimethylaminonapthalene (acrylodan)-labeled peptide, mimicking PKC phosphorylation sites, was synthesized.
• The fluorescence change of the labeled peptide upon phosphorylation by PKC was measured.
• PKC activity was assessed by monitoring the decrease in fluorescence intensity.
• The assay's sensitivity, specificity, and inhibition by staurosporine were evaluated.

Main Results:

• Phosphorylation of the acrylodan-peptide by PKC resulted in a 20% decrease in fluorescence.
• The fluorescence decrease was dependent on PKC, calcium, phosphatidylserine, diacylglycerol, and ATP.
• The assay demonstrated high sensitivity, detecting as little as 0.02 nM PKC.
• No significant fluorescence change was observed with other kinases, indicating high specificity.
• Staurosporine inhibited the fluorescence decrease with an IC50 of 2 nM.

Conclusions:

• The fluorescence decrease of the acrylodan-peptide provides a robust and continuous fluorescence assay for PKC activity.
• This assay is highly sensitive and specific, suitable for measuring PKC in purified enzymes and crude brain homogenates.
• The developed method offers a valuable tool for biochemical and cell biology research involving PKC signaling.