PTP1B promotes focal complex maturation, lamellar persistence and directional migration

Abstract

SummaryPrevious findings established that ER-bound PTP1B targets peripheral cell-matrix adhesions and positively regulates cell adhesion to fibronectin. Here we show that PTP1B enhances focal complex lifetime at the lamellipodium base, delaying their turnover and facilitating a-actinin incorporation. We demonstrate the presence of catalytic PTP1BD181A-a-actinin complexes at focal complexes. Kymograph analysis revealed that PTP1B contributes to lamellar protrusion persistence and directional cell migration. Pull-down and FRET analysis also showed that PTP1B is required for efficient integrin-dependent downregulation of RhoA and upregulation of Rac1 during spreading. A substrate trap strategy revealed that FAK/Src recruitment and Src activity are essential for the generation of PTP1B substrates in adhesions. PTP1B targets the negative regulatory site of Src (phosphotyrosine 529), paxillin and p130Cas at peripheral cell-matrix adhesions. We postulate that PTP1B modulates more than one pathway required for focal complex maturation and membrane protrusion, including aactinin-mediated cytoskeletal anchorage, integrin-dependent activation of the FAK/Src signaling pathway, and RhoA and Rac1 GTPase activity. By doing so, PTP1B contributes to coordinated adhesion turnover, lamellar stability and directional cell migration.

Protein tyrosine phosphatase PTP1B in cell adhesion and migration

“…In support to this notion, Bimolecular Fluorescence Complementation (BiFC) analysis revealed the presence of catalytic PTP1B/α-actinin complexes overlapping with paxillin adhesions at lamellar extensions. 28 In addition, we observed that small paxillin adhesions assembled during lamellar protrusion in KO cells did not incorporate α-actinin efficiently and were quickly disassembled. 28 In contrast, most adhesions assembled during lamellar protrusion in WT cells incorporated α-actinin and grew in size.…”

“…Visual inspection of cell morphology and kymograph analysis of the leading edge further revealed that migration of KO cells was characterized by fast extension/retraction of lamella produced in multiple directions, while WT cells persistently extended a broad lamella in the direction of movement. 2,28 Remarkably, neurons from hippocampus and retina transfected with a dominant negative PTP1B construct, displayed axonal growth cones with similar lamellar alterations as those observed in the leading edge of KO fibroblasts. Consistently, axons also showed reduced net elongation rate and increased pause times compared with axons of control neurons.…”

“…[24][25][26][27] In a recent quantitative study, we analyzed the intrinsic motility and migration parameters of PTP1B-null cells (KO cells) in an isotropic 2-D fibronectin substratum. 28 Directionality and average velocity of KO cells were significantly reduced when compared with KO cells reconstituted with wild-type PTP1B (WT cells). These effects could be partially explained by a higher tendency of KO cells to pause during migration.…”

“…We found that adhesions assembled during lamellar protrusions and contacted with ER tubules containing wild-type GFP-PTP1B, had average lifetimes five times longer than those contacted with ER tubules bearing the catalytically inactive mutant GFP-PTP1B (C215S). 28 In addition, short-lived adhesions, which are more abundant in KO cells, displayed higher paxillin disassembly rates than those in WT cells. These results establish that by modulating adhesion lifetimes, ER-bound PTP1B promotes persistent lamellar protrusion and directional migration (Fig.…”

Journey to the Center of the Mitochondria Guided by the Tail Anchor of Protein Tyrosine Phosphatase 1B

“…A spatial subcellular gradient of the activity of PTP1B has been proposed to account for observations of its interactions with an artificial substrate 29 . The specific roles of ER-bound PTP1B at adhesions sites 30,31 and cell-cell junctions 32 have also been explored. These investigations highlight important and distinct physiological roles for PTP1B subpopulations distributed across the cell.…”