Role of 3′-phosphoinositides in oncogenic KRAS-induced modulation of shape and motility of airway epithelial cells
The authors' previous study demonstrated that oncogenic KRAS modulates the shape and motility of airway epithelial cells. To explore detailed mechanism mediating these events, the possible involvement of phosphatidylinositides (PIP) was investigated. The intracellular localization of PIP was visualized with a pleckstrin homology domain-enhanced green fluorescent protein (EGFP) construct. PIP accumulated at the leading edges of polarizing epithelial cells, while they co-localized with cortical actin at cell-cell contacts, suggesting that PIP play important roles in the cytoskeletal organization. Transduction of oncogenic KRAS induced multiple pseudopodia and disrupted cortical actin, enhancing motility. A mitogen activated protein kinase kinase (MEK) inhibitor reduced the accumulation of PIP at membranes and development of pseudopodia, and restored stable cortical actin, reducing the motility. A phosphoinositide 3-kinase (PI3K) inhibitor also reduced accumulation of PIP at membranes, formation of pseudopodia and motility, but its effect on cortical actin was indistinct. The KRAS V12/S35 mutant, activating only the MEK pathway, induced multiple pseudopodia and disrupted the cortical actin. The KRAS V12/C40 mutant, activating only the PI3K pathway, also induced pseudopodia, but its effect on cortical actin was obscure. Taken together, oncogenic KRAS could cause the accumulation of PIP via the PI3K and MEK pathways and modulate the cell shape and migration.
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