MICROTUBULE-DEPENDENT POSITIONING OF PROTEIN TYROSINE PHOSPHATASE PTP1B IN CELL-MATRIX ADHESIONS

ANA E. GONZÁLEZ S. WUSENER; CECILIA CONDE; ALFREDO CÁCERES; CARLOS O. ARREGUI

Villa Carlos Paz, provincia de Córdoba, Argentina

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

PTP1B is an ubiquitous ER-bound tyrosine phosphatase implicated in a variety of cellular processes; thus, it requires a precise subcellular targeting.. PTP1B has the potential for substrate dephosphorylation throughout the branching network occupied by the ER. Here, we provide new insights on the mechanism through which PTP1B is targeted to cell-matrix adhesion sites. We developed a microscopy-based assay for quantifying coincidence events between microtubules (MTs), PTP1B and cell-matrix adhesions in B16F1 melanoma cells and fibroblasts. We found tha GFP-PTP1B bearing the substrate-trapping mutation D181A (DA) localized at MTs plus-ends in cell matrix adhesion visualized by interference reflection microscopy. ER/MT dissociation prevented PTP1B-DA but not MT targeting to the adhesion sites. Similar results were observed using the protein CLIP-170 as a marker of growing MT plus ends. PTP1B-DA at MT plus ends localized mostly at the distal tips of foci containing paxillin, and to a less degree, at foci containing zyxin, markers of nascent and mature adhesions, respectively. TIRFM confirmed that coincidence events occurred near the ventral cell surface. Our results suggest that PTP1B is positioned to the distal tip of newly forming cell matrix adhesion sites through the dynamic activity of MTs. PTP1B may contribute to the maturation of cell-matrix foci. Supported by ANPCyTSupported by ANPCyT