Mhamane, Amit2018-04-122018-04-122017http://hdl.handle.net/2003/3683310.17877/DE290R-18834Autocatalytic activation of Epidermal Growth Factor Receptor (EGFR) at the plasma membrane increases the sensitivity of the cell to extracellular growth factors but can also generate spontaneous receptor activation in the absence of stimulation. As a mechanism to control EGFR phosphorylation at the plasma membrane, receptor endocytosis and vesicular trafficking relocalizes activated, phosphorylated EGFR to perinuclear compartments rich in Protein Tyrosine Phosphatases (PTPs), such as PTPN1, which dephosphorylate and inactivate the receptor. Although the role of few PTPs in regulating EGFR phosphorylation is known, it is unclear how PTPs that are spatially segregated in distinct cellular compartments, modulate EGFR autocatalytic activation and hence its downstream signaling. Through quantitative imaging of EGFR phosphorylation upon genetic perturbations of classical PTPs and EGFR-PTP interactions, we identified endoplasmic reticulum (ER) associated PTPN2 and plasma membrane associated receptor-like PTPRG/J as strong, direct negative regulators of EGFR. Using single cell measurements of phosphorylation of the EGFR downstream signaling tyrosine residue Y1068, we generated a spatial-temporal reactivity map to identify local phosphatase activity. By negatively regulating EGFR phosphorylation, we deduced the role of PTPN2/PTPRJ in determining signal duration: a function that is coupled to vesicular trafficking. Furthermore, by maintaining the plasma membrane density of EGFR due to its interaction with ligandless EGFR and dephosphorylation of EGFR at Y1045 - a cCbl-ubiquitin ligase binding site, PTPN2 participates in a spatially established negative-feedback that is mediated by vesicular recycling. Through its activity on ligandless EGFR at plasma membrane, PTPRG regulates the autocatalytic activity of EGFR and influences the responsiveness of a cell to EGF dose. Altogether our findings indicate that by spatially segregating PTPs with different functional relationships to EGFR, the cell is able to sense and respond to its environment.enEGFRPTPSpatial dynamics570doctoral thesisPlasmamembranEpidermaler Wachstumsfaktor