The process of GEEC endocytosis and signal amplification atthe plasmamembrane

In metazoan cells,the cytosoland the extracellular milieu are separated bythe plasmamembrane (PM). The communication between these two chemically distinct environments is brought about by highly regulated endocytic and signaling processes. One such process, namely the GPI-Anchored Proteinenriched Early EndosomalCompartment (GEEC) endocyticpathway hasbeen the focus of my thesis work. While a majority of GPI-APs and a large bulk of PM are internalized via the GEECpathway,itsmolecular mechanism remained unclear. The results from my experiments revealed that a coupling of two GTPasesand subsequent dynamic actin polymerization at the PM is required for efficient operation of the GEEC pathway. Furthermore, the post-endocytic fate of GPI-APs endocytosed via GEECs was dictated by the membrane cholesterol composition and extracellular pH. Together, these results impliedthat the GEEC pathway is a constitutive internalization portal that is highly sensitive to the extracellular environment and cortical actin remodeling.

In my talk, I will primarily discuss the molecular regulationand cargo sorting features of the GEEC pathway. In addition, I will briefly introduce the role of cortical actin in facilitating receptor signal amplification at the PM, whichaids in sensitive yet robust signaling response inside the cell.