Phosphatidylcholine hydrolysis and c-myc expression are in collaborating mitogenic pathways activated by colony-stimulating factor 1.

Abstract

Stimulation of diglyceride production via phospholipase C (PLC) hydrolysis of phosphatidylcholine was an early event in the mitogenic action of colony-stimulating factor 1 (CSF-1) in the murine macrophage cell line BAC1.2F5 and was followed by a second phase of diglyceride production that persisted throughout the G1 phase of the cell cycle. Addition of phosphatidylcholine-specific PLC (PC-PLC) from Bacillus cereus to the medium of quiescent cells raised the intracellular diglyceride concentration and stimulated [3H]thymidine incorporation, although PC-PLC did not support continuous proliferation. PC-PLC treatment did not induce tyrosine phosphorylation or turnover of the CSF-1 receptor. The major protein kinase C (PKC) isotype in BAC1.2F5 cells was PKC-delta. Diglyceride production from PC-PLC did not target PKC-delta, since unlike phorbol esters, PC-PLC treatment neither decreased the electrophoretic mobility of PKC-delta nor increased the amount of GTP bound to Ras, and PC-PLC was mitogenically active in BAC1.2F5 cells in which PKC-delta was downregulated by prolonged treatment with phorbol ester. PC-PLC mimicked CSF-1 action by elevating c-fos and junB mRNAs to 40% of the level induced by CSF-1; however, PC-PLC induced c-myc mRNA to only 5% of the level in CSF-1-stimulated cells. PC-PLC addition to CSF-1-dependent BAC1.2F5 clones that constitutively express c-myc increased [3H]thymidine incorporation to 86% of the level evoked by CSF-1 and supported slow growth in the absence of CSF-1. Therefore, PC-PLC is a component of a signal transduction pathway leading to transcription of c-fos and junB that collaborates with c-myc and is independent of PKC-delta and Ras activation.

Reversion of Ras- and Phosphatidylcholine-hydrolyzing Phospholipase C-mediated Transformation of NIH 3T3 Cells by a Dominant Interfering Mutant of Protein Kinase C λ Is Accompanied by the Loss of Constitutive Nuclear Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase Activity

“…Constitutively active mutants of Ras relay signals through several parallel pathways (37,38,40,70). Hydrolysis of phosphatidylcholine has also been reported to be involved in several signaling pathways (20,27,71,72). However, the ERKs are the only known substrates for MEK.…”

CSF-1 Receptor Signaling in Myeloid Cells

“…PI3K-independent pathways of CSF-1R-mediated survival involve phospholipase C (PLC) (Xu et al 1993) and Fms-interacting protein (FIMP) (Mancini et al 2004). PI3K and PLC independently enhance survival by controlling glucose uptake (Chang et al 2009).…”

Regulation of Urokinase-Type Plasminogen Activator Gene Transcription by Macrophage Colony-Stimulating Factor

“…Unlike the platelet-derived growth factor receptor, CSF-1R does not activate phospholipase C-␥ (21), and there is no associated increase in phosphatidylinositol turnover (34,81). An alternative route for diacylglycerol production may be by activation of a phosphatidylcholine-specific phospholipase C (83).…”