To nucleate the assembly of branched actin filaments, Arp2/3 needs to be activated by a nucleation promoting factor (NPF)

TLS Online TPP Program

#Id: 9660

#Unit 4. Cell Communication and Cell Signaling

Many RTKs and cytokine receptors specifically activate the γ isoform (PLCγ), which contains an SH2 domain.

TLS Online TPP Program

#Id: 9661

#Unit 4. Cell Communication and Cell Signaling

Activated RTKs and cytokine receptors promote PLCγ activity in two ways: 

By localizing PLCγ to the membrane

By phosphorylating PLCγ

TLS Online TPP Program

#Id: 9662

#Unit 4. Cell Communication and Cell Signaling

The SH2 domains of PLCγ bind to specific phosphotyrosines on the activated RTKs and cytokine receptors, thus positioning PLCγ close to PIP2.

TLS Online TPP Program

#Id: 9663

#Unit 4. Cell Communication and Cell Signaling

Kinase activity associated with receptor activation phosphorylates tyrosines on the bound PLCγ, enhancing its hydrolase activity. 

TLS Online TPP Program

#Id: 9664

#Unit 4. Cell Communication and Cell Signaling

Activated RTKs and cytokine receptors initiate another phosphoinositide pathway by recruiting PI-3 kinase to the cytosolic surface of the plasma membrane.

TLS Online TPP Program

#Id: 9665

#Unit 4. Cell Communication and Cell Signaling

PI-3 kinase contains SH2 domain which binds to phosphotyrosines on the activated RTKs and cytokine receptors