Figure 3.

Disassembly of actin filaments can spontaneously activate PLC in certain cells: a model involving SFK. (A) Src family kinases (SFK) can be recruited to the plasma membrane due to their myristoylation, but the enzymes hardly have access to its substrate PLC-γ because of the actin cytoskeleton to which SFK is often associated. (B) When the actin cytoskeleton is disassembled, the physical barrier is essentially removed. SFK now gains access to PLC-γ and activates it. The phosphorylated PLC-γ now hydrolyzes the plasma membrane PIP2 to produce InsP₃, a Ca²⁺-mobilizing second messenger acting on the receptor ion channel on the endoplasmic reticulum (ER). In the case of starfish egg (Astropecten aranciacus), disassembly of subplasmalemmal F-actin with Latrunculin-A and other drugs leads to increased production of InsP₃ and the consequent rise of intracellular Ca²⁺ levels in the form of repetitive waves.