Protein tyrosine phosphatase phi regulates paxillin tyrosine phosphorylation and mediates colony-stimulating factor 1-induced morphological changes in macrophages.
Removal of colony-stimulating factor 1 (CSF-1) causes macrophages to round up and to increase their expression of protein tyrosine phosphatase phi (PTP phi). This is accompanied by the disruption of focal complexes and the formation of ruffles. Here we have overexpressed wild-type (WT) PTP phi and a phosphatase-inactive (C325S) mutant in a macrophage cell line in the presence and absence of CSF-1. In the presence of CSF-1, WT PTP phi induces cell rounding and ruffle formation, while C325S PTP phi has no effect. In contrast, in CSF-1-starved cells, C325S PTP phi behaves in a dominant negative fashion, preventing rounding and ruffling. Furthermore, C325S PTP phi increases adhesion in cycling cells, while WT PTP phi enhances motility. In WT PTP phi-overexpressing cells, the focal contact protein paxillin is selectively depleted from focal complexes and specifically dephosphorylated on tyrosine. In contrast, paxillin is hyperphosphorylated in C325S PTP phi-expressing cells. Moreover, a complex containing PTP phi, paxillin, and a paxillin-associated tyrosine kinase, Pyk2, can be immunoprecipitated from macrophage lysates, and the catalytic domain of PTP phi selectively binds paxillin and Pyk2 in vitro. Although PTP phi and Pyk2 do not colocalize with paxillin in focal complexes, all three proteins are colocalized in dorsal ruffles. The results suggest that paxillin is dephosphorylated by PTP phi in dorsal ruffles, using Pyk2 as a bridging molecule, resulting in a reduced pool of tyrosine-phosphorylated paxillin available for incorporation into focal complexes, thereby mediating CSF-1 regulation of macrophage morphology, adhesion, and motility.
Pixley
F J
FJ
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Lee
P S
PS
Condeelis
J S
JS
Stanley
E R
ER
D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D020134:Catalytic Domain; D002448:Cell Adhesion; D002455:Cell Division; D002460:Cell Line; D002465:Cell Movement; D002470:Cell Survival; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007668:Kidney / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism*; D014945:Wound Healing
D003598:Cytoskeletal Proteins; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D020033:Protein Isoforms; D014443:Tyrosine; D016173:Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D017027:Protein Tyrosine Phosphatases; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3