Phosphorylation of GMFγ by c-Abl coordinates lamellipodial and focal adhesion dynamics to regulate airway smooth muscle cell migration.pdf

Airway smooth muscle cells require coordinated protrusion and focal adhesion dynamics to
migrate properly. However, the signaling cascades that connect these two processes remain
incompletely understood. GMFγ has been implicated in inducing actin debranching and inhibiting
nucleation. In this study, we discovered that GMFγ phosphorylation at Y104 regulates human
airway smooth muscle cell migration. Utilizing high-resolution microscopy coupled with 3D-object
based quantitative image analysis software Imaris 9.2.0, phosphomimetic mutant Y104D-GMFγ
was enriched at nascent adhesions along the leading edge where it recruited activated N-WASP
(pY256) to promote actin-branch formation, which enhanced lamellipodial dynamics and limited
the growth of focal adhesions. Unexpectedly, we found that non-phosphorylated mutant Y104FGMFγ
was enriched in growing adhesions where it promoted a linear branch organization, focal
adhesion clustering, and recruited zyxin to increase maturation, thus inhibiting lamellipodial
dynamics and cell migration. The localization of GMFγ between the leading edge and focal
adhesions was dependent upon myosin activity. Furthermore, c-Abl tyrosine kinase regulated the
GMFγ phosphorylation-dependent processes. Together, these results unveil the importance of
GMFγ phosphorylation in coordinating lamellipodial and focal adhesion dynamics to regulate cell
migration.