Transmodulation between phospholipase D and c-Src enhances cell proliferation

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Phospholipase D (PLD) is involved in signal transduction pathways activated by mitogenic protein tyrosine kinases.
• The interaction between PLD and kinases like c-Src is crucial for cellular signaling but not fully understood.

Purpose of the Study:

• To investigate the direct interaction and functional relationship between Phospholipase D (PLD) isoforms (PLD1 and PLD2) and c-Src tyrosine kinase.
• To elucidate the role of PLD catalytic activity in modulating c-Src signaling pathways and cellular proliferation.

Main Methods:

• Co-immunoprecipitation to demonstrate protein-protein interactions.
• In vitro kinase assays to assess enzymatic activity.
• Western blotting to detect protein phosphorylation.
• Cell proliferation assays.

Main Results:

• PLD2 and PLD1 are directly tyrosine phosphorylated by c-Src, with PLD2 being more significantly affected.
• Epidermal growth factor (EGF) induces PLD2 phosphorylation and its interaction with c-Src in A431 cells.
• PLD catalytic activity, but not its lipid-hydrolyzing function, is critical for up-regulating c-Src kinase activity, paxillin phosphorylation, and ERK activity.
• Coexpression of PLD and c-Src synergistically enhances cellular proliferation.

Conclusions:

• c-Src directly phosphorylates PLD, acting as its kinase.
• PLD, through its catalytic activity, acts as an activator of c-Src kinase.
• This reciprocal modulation (transmodulation) between c-Src and PLD amplifies mitogenic signaling, contributing to cellular proliferation.