Membrane-associated phospholipase D activity in neural cell line PC12

Area of Science:

• Biochemistry
• Cell Biology
• Neuroscience

Background:

• Phospholipase D (PLD) is a key enzyme in cell signaling.
• PC12 cells are a neuronal cell line widely used in research.
• Calcium ions (Ca2+) play crucial roles in cellular processes.

Purpose of the Study:

• To investigate the mechanism of phospholipase D (PLD) activation in PC12 cells.
• To determine the role of extracellular calcium in Cch-mediated PLD activation.
• To characterize the types of PLD activity present in PC12 cells.

Main Methods:

• PC12 cells were stimulated with carbachol (Cch) or phorbol 12-myristate 13-acetate (PMA).
• Radioactive [3H]phosphatidylbutanol ([3H]PBut) production was measured.
• Extracellular calcium was depleted to assess its role.
• Exogenous [3H]phosphatidylcholine was used to examine PLD activity in membrane fractions, assessing oleate- and GTPγS-dependence.

Main Results:

• Cch and PMA induced [3H]PBut production in PC12 cells.
• Cch-mediated PLD activation was abolished by extracellular calcium depletion, indicating a requirement for Ca2+ influx.
• PC12 cell membrane PLD activity was highly oleate-dependent and independent of GTPγS.
• This contrasts with HL60 cells, where PLD is GTPγS-dependent.
• High concentrations of Ca2+ and Mg2+ inhibited the oleate-dependent PLD activity in PC12 membranes.

Conclusions:

• Calcium influx is necessary for carbachol-stimulated PLD activation in PC12 cells.
• PC12 cell PLD exhibits oleate-dependent activity, differing from GTPγS-dependent PLD in other cell types.
• Calcium may not directly activate PLD but acts through intermediate Ca2+-dependent mechanisms in Cch-stimulated PC12 cells.