Protease-activated protein kinase C in rat liver

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Signaling

Background:

• Protein kinase C (PKC) is crucial in cellular signaling pathways.
• Proteolytic activation of PKC can alter its function.
• Investigating PKC activation mechanisms is vital for understanding cellular regulation.

Purpose of the Study:

• To characterize protease-activated protein kinase C in regenerating rat liver.
• To elucidate the mechanisms and conditions for PKC proteolytic activation.
• To identify the molecular properties of the resulting active kinase forms.

Main Methods:

• Analysis of protein kinase activity in regenerating rat liver extracts.
• Biochemical characterization of enzyme properties, including molecular mass and activation conditions.
• Investigating the effects of proteolysis, calcium, and phospholipids on PKC activity.

Main Results:

• Elevated protein kinase activity phosphorylating ribosomal protein S6 and histones was observed.
• Two distinct protease-activated forms of protein kinase C were identified: protein kinase M (Mr 45,000) and another kinase (Mr 80,000).
• Activation conditions varied, with protein kinase M formation favored at higher ionic strength and alkaline pH, potentially linked to Na+/H+ exchanger activity, while the Mr 80,000 form appeared under lower ionic strength.

Conclusions:

• Regenerating rat liver exhibits distinct protease-activated forms of protein kinase C.
• The formation of protein kinase M is dependent on specific ionic strength and pH conditions, possibly involving plasma membrane ion exchangers.
• The physiological roles of these protease-activated PKC forms in liver function require further investigation.