Reduced focal adhesion kinase and paxillin phosphorylation in BCR-ABL-transfected cells.
BACKGROUND
BCR-ABL formation is critical to oncogenic transformation in chronic myelogenous leukemia and has been implicated as a key event leading to alterations in cytoskeletal structures and adhesion in the leukemic cells. The authors therefore investigated the effect of p210(BCR-ABL) on actin polymerization as well as on the expression and phosphorylation state of the adhesion proteins paxillin and focal adhesion kinase (FAK).


METHODS
Transfection with BCR-ABL constructs abrogated the ability of NIH 3T3 fibroblasts to adhere and the cells underwent striking morphologic changes.


RESULTS
Scanning electron microscopy revealed that the cells lost their elongated appearance and became rounded. This alteration was associated with significantly reduced actin polymerization. In addition, steady-state levels of paxillin and FAK protein were increased. However, while the overall level of phosphotyrosines was also increased, the amount of tyrosine phosphorylated paxillin and FAK was reduced in the BCR-ABL-transfected cells as compared to the parental cells. Culture on extracellular fibronectin matrix partially reversed the morphologic changes and resulted in a return, albeit incomplete, of filamentous actin in BCR-ABL-transfected 3T3 fibroblasts. In addition, phosphorylation of paxillin and FAK in the BCR-ABL-transfected NIH 3T3 cells was restored.


CONCLUSIONS
The authors conclude that, in the current system, transfection of BCR-ABL attenuates FAK and paxillin phosphorylation and reduces actin polymerization, events accompanied by significant alterations in cellular morphology. The observation that exposure of the cells to fibronectin partially reverses all these changes suggests that the focal adhesion proteins and actin structures nevertheless remain responsive to signaling from the outside.
Cheng
Keding
K
Department of Bioimmunotherapy, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Kurzrock
Razelle
R
Qiu
Xiangguo
X
Estrov
Zeev
Z
Ku
Stella
S
Dulski
Kim M
KM
Wang
Jean Y J
JY
Talpaz
Moshe
M
D016475:3T3 Cells; D000199:Actins / Q000648:ultrastructure; D000818:Animals; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure; D005353:Fibronectins / Q000648:ultrastructure; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022001:Focal Adhesions; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014162:Transfection
D000199:Actins; D003598:Cytoskeletal Proteins; D005353:Fibronectins; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; C496051:Ptk2 protein, mouse