Colony-stimulating factor 1 activates protein kinase C in human monocytes

Area of Science:

• Cellular signaling pathways
• Monocyte biology
• Signal transduction

Background:

• Colony-stimulating factor 1 (CSF-1) is essential for monocyte survival, proliferation, and differentiation.
• Previous studies linked the CSF-1 receptor to a pertussis toxin-sensitive G protein and CSF-1-induced Na+ influx.

Purpose of the Study:

• To investigate protein kinase C (PKC) activation as an intracellular signaling event downstream of the CSF-1 receptor.
• To elucidate the role of lipid metabolism, specifically phosphatidylcholine (PC) and phosphatidylinositol (PI) turnover, in CSF-1 signaling.

Main Methods:

• Monocyte isolation and stimulation with CSF-1.
• Measurement of protein kinase C translocation from cytosol to membrane fractions.
• Analysis of phospholipid levels (PC and PI) and inositol phosphate production.
• Assessment of PC hydrolysis to diacylglycerol (DAG) and phosphorylcholine.
• Evaluation of Na+ influx inhibition by PKC inhibitors (staurosporine, H7, HA1004) and pertussis toxin pretreatment.

Main Results:

• CSF-1 stimulated the translocation of PKC activity to membrane fractions in a pertussis toxin-sensitive manner.
• CSF-1 induced hydrolysis of PC, but not PI, leading to increased DAG and phosphorylcholine production.
• CSF-1 stimulation of Na+ influx was inhibited by staurosporine and H7, indicating a role for PKC.
• Pertussis toxin inhibited CSF-1-induced PC turnover.

Conclusions:

• CSF-1 activates protein kinase C in human monocytes through a pertussis toxin-sensitive pathway.
• The signaling cascade involves the hydrolysis of phosphatidylcholine, contributing to CSF-1-mediated effects like Na+ influx.
• Protein kinase C plays a role in mediating CSF-1-induced sodium influx in monocytes.