Constitutive Macropinocytosis in Oncogene-transformed Fibroblasts Depends on Sequential Permanent Activation of Phosphoinositide 3-Kinase and Phospholipase C
AUTOR(ES)
Amyere, Mustapha
FONTE
The American Society for Cell Biology
RESUMO
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 p85α 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 p85α 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=15006Documentos Relacionados
- Novel revertants of H-ras oncogene-transformed R6-PKC3 cells.
- Growth factor requirements of oncogene-transformed NIH 3T3 and BALB/c 3T3 cells cultured in defined media.
- Depletion of c-myc with specific antisense sequences reverses the transformed phenotype in ras oncogene-transformed NIH 3T3 cells.
- Suppression of tumorigenicity in hybrids of normal and oncogene-transformed CHEF cells.
- Prevention of tumorigenesis of oncogene-transformed rat fibroblasts with DNA site inhibitors of poly(ADP ribose) polymerase.