The tyrosine phosphatase DEP-1 induces cytoskeletal rearrangements, aberrant cell-substratum interactions and a reduction in cell proliferation.
The receptor protein tyrosine phosphatase density-enhanced phosphatase-1 (DEP-1) has been implicated in aberrant cancer cell growth and immune cell function, however, its function within cells has yet to be properly elucidated. To investigate the cellular function of DEP-1, stable cell lines inducibly expressing DEP-1 were generated. Induction of DEP-1 expression was found to decrease PDGF-stimulated tyrosine phosphorylation of a number of cellular proteins including the PDGF receptor, and to inhibit growth factor-stimulated phosphorylation of components of the MAPK pathway, indicating that DEP-1 antagonised PDGF receptor signalling. This was supported by data showing that DEP-1 expression resulted in a reduction in cell proliferation. DEP-1-expressing cells had fewer actin-containing microfilament bundles, reduced vinculin and paxillin-containing adhesion plaques, and were defective in interactions with fibronectin. Defective cell-substratum adhesion correlated with lack of activation of FAK in DEP-1-expressing cells. Time-lapse interference reflection microscopy of live cells revealed that although small focal contacts at the leading edge were generated in DEP-1-expressing cells, they failed to mature into stable focal adhesions, as found in control cells. Further motility analysis revealed that DEP-1-expressing cells retained limited random motility, but showed no chemotaxis towards a gradient of PDGF. In addition, cell-cell contacts were disrupted, with a change in the localisation of cadherin from discrete areas of cell-cell contact to large areas of membrane interaction, and there was a parallel redistribution of beta-catenin. These results demonstrate that DEP-1 is a negative regulator of cell proliferation, cell-substratum contacts, motility and chemotaxis in fibroblasts.
Kellie
Stuart
S
School of Molecular and Microbial Sciences, Institute for Molecular Bioscience and CRC for Chronic Inflammatory Diseases, University of Queensland, Brisbane, QLD 4072, Australia. s.kellie@mailbox.uq.edu.au
Craggs
Graham
G
Bird
Ian N
IN
Jones
Gareth E
GE
D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002450:Cell Communication / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022001:Focal Adhesions / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D051379:Mice; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology
D006133:Growth Substances; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; D054645:Protein Phosphatase 1; C486288:PTPRJ protein, human; D017027:Protein Tyrosine Phosphatases; C098066:Ptprj protein, mouse; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3