Phosphorylation of c-Src on tyrosine 527 by another protein tyrosine kinase

Area of Science:

• Cellular and Molecular Biology
• Biochemistry
• Signal Transduction

Background:

• Cellular Src (c-Src) is a non-receptor protein tyrosine kinase.
• c-Src activity is regulated by phosphorylation, particularly at tyrosine residue 527 (Tyr527), which inhibits its kinase activity.
• The specific kinase responsible for Tyr527 phosphorylation remains unidentified, with possibilities including autophosphorylation or an external kinase.

Purpose of the Study:

• To determine whether the phosphorylation of Tyr527 in c-Src is an autophosphorylation event or mediated by another cellular kinase.
• To elucidate the mechanism of negative regulation of c-Src kinase activity.

Main Methods:

• Utilized a modified form of c-Src lacking intrinsic kinase activity.
• Examined Tyr527 phosphorylation in mouse cells with targeted disruption of both endogenous src alleles (Src-null cells).
• Compared Tyr527 phosphorylation levels in Src-null cells versus cells expressing endogenous Src.

Main Results:

• Phosphorylation of the inactive c-Src mutant on Tyr527 occurred at comparable levels in both Src-null cells and cells expressing endogenous Src.
• This indicates that a kinase other than c-Src itself is responsible for Tyr527 phosphorylation.

Conclusions:

• The phosphorylation of Tyr527, a key inhibitory modification of c-Src, is mediated by an external cellular protein tyrosine kinase.
• This finding clarifies a critical regulatory mechanism of c-Src activity and cellular signaling pathways it influences.