Amyere, Mustapha
[UCL]
Payrastre, B
Krause, U
Van Der Smissen, Patrick
[UCL]
Veithen, A.
Courtoy, Pierre J.
[UCL]
Macropinocytosis results from the closure of lamellipodia generated by membrane ruffling, thereby reflecting cortical actin dynamics. Both transformation of Rat-1 fibroblasts by v-Src or K-Ras and stable transfection for expression of dominant-positive, wild-type phosphoinositide 3-kinase (PI3K) regulatory subunit p85 alpha constitutively led to stress fiber disruption, cortical actin recruitment, extensive ruffling, and macropinosome formation, as measured by a selective acceleration of fluid-phase endocytosis. These alterations closely correlated with activation of PI3K and phosphatidylinositol-specific phospholipase C (PI-PLC), as assayed by 3-phosphoinositide synthesis in situ and in vitro and inositol 1, 4,5 trisphosphate steady-state levels, respectively; they were abolished by stable transfection of v-Src-transformed cells for dominant-negative truncated p85 alpha expression and by pharmacological inhibitors of PI3K and PI-PLC, indicating a requirement for both enzymes. Whereas PI3K activation resisted PI-PLC inhibition, PI-PLC activation was abolished by a PI3K inhibitor and dominant-negative transfection, thus placing PI-PLC downstream of PI3K. Together, these data suggest that permanent sequential activation of both PI3K and PI-PLC is necessary for the dramatic reorganization of the actin cytoskeleton in oncogene-transformed fibroblasts, resulting in constitutive ruffling and macropinocytosis.
Bibliographic reference |
Amyere, Mustapha ; Payrastre, B ; Krause, U ; Van Der Smissen, Patrick ; Veithen, A. ; et. al. Constitutive macropinocytosis in oncogene-transformed fibroblasts depends on sequential permanent activation of phosphoinositide 3-kinase and phospholipase C.. In: Molecular biology of the cell, Vol. 11, no. 10, p. 3453-67 (2000) |
Permanent URL |
http://hdl.handle.net/2078.1/8657 |