title: ER-bound PTP1B is targeted to newly forming cell-matrix adhesions.
abstract: Here, we define the mechanism through which protein tyrosine phosphatase 1B (PTP1B) is targeted to cell-matrix adhesion sites. Green fluorescent protein (GFP)-labeled PTP1B bearing the substrate-trapping mutation D181A was found in punctate structures in lamellae. The puncta co-localized with focal adhesion kinase (FAK) and Src, and defined the distal tips of cell-matrix adhesion sites identified with paxillin and vinculin. PTP1B is largely associated with the external face of the endoplasmic reticulum (ER) and the puncta develop from ER projections over cell-matrix adhesion sites, a process dependent on microtubules. Deletion of the ER-targeting sequence resulted in cytosolic localization and altered the distribution of PTP1B at cell-matrix foci, whereas mutations disrupting interactions with Src homology 3 (SH3) domains, and the insulin and cadherin receptors had no effect. PTP1B recognizes substrates within forming adhesion foci as revealed by its preferential association with paxillin as opposed to zyxin-containing foci. Our results suggest that PTP1B targets to immature cell-matrix foci in newly forming lamellae by dynamic extensions of the ER and contributes to the maturation of these sites.
authors.affiliation: Instituto de Investigaciones Biotecnológicas, IIB-INTECH, Universidad de San Martín, 1650 San Martín, Buenos Aires, Argentina.
authors.forename: Mariana V
authors.initials: MV
authors.lastname: Hernández
authors.forename: Maria G Davies
authors.initials: MG
authors.lastname: Sala
authors.forename: Janne
authors.initials: J
authors.lastname: Balsamo
authors.forename: Jack
authors.initials: J
authors.lastname: Lilien
authors.forename: Carlos O
authors.initials: CO
authors.lastname: Arregui
mesh_terms: D000818:Animals; D015153:Blotting, Western; D021982:Cell-Matrix Junctions / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D019085:Fluorescent Antibody Technique, Direct; D017353:Gene Deletion; D018390:Gene Targeting; D051379:Mice; D018345:Mice, Knockout; D018715:Microscopy, Video; D051419:Paxillin / Q000378:metabolism; D011233:Precipitin Tests; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D051419:Paxillin; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; C516609:Ptpn1 protein, mouse