PTP alpha regulates integrin-stimulated FAK autophosphorylation and cytoskeletal rearrangement in cell spreading and migration.
We investigated the molecular and cellular actions of receptor protein tyrosine phosphatase (PTP) alpha in integrin signaling using immortalized fibroblasts derived from wild-type and PTP alpha-deficient mouse embryos. Defects in PTP alpha-/- migration in a wound healing assay were associated with altered cell shape and focal adhesion kinase (FAK) phosphorylation. The reduced haptotaxis to fibronectin (FN) of PTP alpha-/- cells was increased by expression of active (but not inactive) PTP alpha. Integrin-mediated formation of src-FAK and fyn-FAK complexes was reduced or abolished in PTP alpha-/- cells on FN, concomitant with markedly reduced phosphorylation of FAK at Tyr397. Reintroduction of active (but not inactive) PTP alpha restored FAK Tyr-397 phosphorylation. FN-induced cytoskeletal rearrangement was retarded in PTP alpha-/- cells, with delayed filamentous actin stress fiber assembly and focal adhesion formation. This mimicked the effects of treating wild-type fibroblasts with the src family protein tyrosine kinase (Src-PTK) inhibitor PP2. These results, together with the reduced src/fyn tyrosine kinase activity in PTP alpha-/- fibroblasts (Ponniah et al., 1999; Su et al., 1999), suggest that PTP alpha functions in integrin signaling and cell migration as an Src-PTK activator. Our paper establishes that PTP alpha is required for early integrin-proximal events, acting upstream of FAK to affect the timely and efficient phosphorylation of FAK Tyr-397.
Zeng
Li
L
Cell Regulation Laboratory, Institute of Molecular and Cell Biology, Singapore 117609, Singapore.
Si
Xiaoning
X
Yu
Wei-Ping
WP
Le
Hoa Thi
HT
Ng
Kwok Peng
KP
Teng
Raymond M H
RM
Ryan
Kenneth
K
Wang
Dennis Z-M
DZ
Ponniah
Sathivel
S
Pallen
Catherine J
CJ
D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D002384:Catalysis; D002448:Cell Adhesion; D002465:Cell Movement; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015151:Immunoblotting; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D011233:Precipitin Tests; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism* / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D011956:Receptors, Cell Surface; D014443:Tyrosine / Q000378:metabolism; D016596:Vinculin / Q000096:biosynthesis
D016895:Culture Media, Serum-Free; D005353:Fibronectins; D016023:Integrins; D011956:Receptors, Cell Surface; D016596:Vinculin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D017027:Protein Tyrosine Phosphatases; C516843:Ptpra protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4