PMID: 23777354

Authors:

Hajicek N, Charpentier TH, Rush JR, Harden TK, Sondek JE

Title:

Auto-inhibition and phosphorylation-induced activation of PLC-gamma isozymes.

Journal:

Biochemistry. 2013 Jun 18.

Abstract:

Multiple extracellular stimuli, such as growth factors and antigens, initiate signaling cascades through tyrosine phosphorylation and activation of phospholipase C (PLC)-gamma isozymes. Like most other PLCs, PLC-gamma1 is basally auto-inhibited by its X-Y linker, which separates the X- and Y-boxes of the catalytic core. The C-terminal SH2 (cSH2) domain within the X-Y linker is the critical determinant for auto-inhibition of phospholipase activity. Release of auto-inhibition requires an intramolecular interaction between the cSH2 domain and a phosphorylated tyrosine, Tyr783, also located within the X-Y linker. The molecular mechanisms that mediate auto-inhibition and phosphorylation-induced activation have not been defined. Here, we describe structures of the cSH2 domain both alone and bound to a PLC-gamma1 peptide encompassing phosphorylated Tyr783. The cSH2 domain remains largely unaltered by peptide engagement. Point mutations in the cSH2 domain located at the interface with the peptide were sufficient to constitutively activate PLC-gamma1 suggesting that peptide engagement directly interferes with the capacity of the cSH2 domain to block the lipase active site. This idea is supported by mutations in a complimentary surface of the catalytic core that also enhanced phospholipase activity.