Question

Cofilin is a protein that binds to actin filaments and speeds up the loss of actin monomers from the minus end. Why might increasing the activity of cofilin cause a crawling cell (or a motile growth cone) to increase its speed of movement?

Answer 1

answer:

Cofilin is a ubiquitous actin-binding factor (ADF) required for the reorganization of actin filaments. ADF/Cofilin family members bind G-actin monomers and depolymerize actin filaments through two mechanisms: severing and increasing the off-rate for actin monomers from the pointed end. Growth cone motility and morphology are based on actin-filament dynamics. it plays an essential role for the rapid turnover of actin filaments by severing and depolymerizing them. The activity of cofilin is repressed by phosphorylation at Ser3 by LIM kinase (LIMK, in which LIM is an acronym of the three gene products Lin-11, Isl-1, and Mec-3) and is reactivated by dephosphorylation by phosphatases, termed Slingshot (SSH). The growth of cones wasfan- like and disorganized by the expression of any of these proteins. The repressive effects on growth cone behavior by LIMK1 expression were significantly rescued by the coexpression of S3A–cofilin or SSH1. it is proven that LIMK1 and SSH1 play critical roles in controlling growth cone motility and morphology and neurite extension by regulating the activity of cofilin and may be involved in signaling pathways that regulate stimulus-induced growth cone guidance. Using various mutants of cofilin,it is proved that the actin-filament-severing activity of cofilin is critical for growth cone motility and neurite extension.