Protein kinase C from small intestine epithelial cells

Area of Science:

• Molecular Biology
• Cellular Physiology
• Biochemistry

Background:

• Protein kinase C (PKC) is a family of enzymes involved in various cellular processes.
• Understanding PKC localization and activation in intestinal epithelial cells is crucial for comprehending cellular signaling.
• Previous research has indicated the potential involvement of PKC in regulating ion transport.

Purpose of the Study:

• To identify and characterize Protein Kinase C activity in rat and rabbit small intestine epithelial cells.
• To investigate the localization and activation requirements of PKC within these cells.
• To explore the potential role of PKC in calcium-mediated ionic transport.

Main Methods:

• Fractionation of rat and rabbit small intestine epithelial cells into cytosolic and membrane components.
• Ion exchange chromatography to resolve PKC activity from other kinases.
• Assays to determine PKC activation by lipids (phosphatidylserine, phosphatidylinositol, diacylglycerols), calcium ions, and phorbol esters (TPA).

Main Results:

• Protein kinase C activity was predominantly found in the cytosolic fraction (approximately 75%).
• PKC activation required phosphatidylserine or phosphatidylinositol and was enhanced by diacylglycerols (diolein, dimyristin) and TPA.
• Basolateral membranes exhibited higher specific PKC activity (four-fold) compared to brush border membranes; calcium activation showed a Ka of 10(-7)M.

Conclusions:

• Protein kinase C is present and active in small intestine epithelial cells, with significant cytosolic localization.
• PKC activation is dependent on specific lipids and calcium ions, consistent with known regulatory mechanisms.
• The differential distribution and calcium sensitivity of PKC in intestinal membranes suggest a key role in regulating ion transport processes.