A Switchable Two-Photon Membrane Tracer Capable of Imaging Membrane-Associated Protein Tyrosine Phosphatase Activities

摘要

The plasma membrane is involved in a variety of important cellular processes such as cell adhesion and cell signaling, most of which are orchestrated by proteins embedded within its lipid bilayer. It is estimated that proteins occupy approximately 50 % of a typical membrane volume, and in mammalian cells, more than one third of all genes encode membrane proteins of different functions. Protein tyrosine phosphatases (PTPs) are signaling enzymes that remove the phosphate group from their protein substrates. One of the most important subclasses of PTPs is the membrane-associated, receptor-like protein tyrosine phosphatases (RPTPs), which are responsible for most of the protein phosphatase activities localized near the plasma membrane. Dysregulation of PTPs, especially RPTPs, has been implicated in a variety of human diseases including cancer, diabetes, and autoimmune disorders. Elevated levels of endogenous RPTP activities are well documented to be closely associated with tumori-genesis in numerous cells and tissues. Effective methods to fluorescently label the plasma membrane of cancer cells and tissues, as well as monitor membrane-localized RPTP activities, are therefore of significant interest in cell signaling and PTP biology. At present, few biochemical techniques are available for such labeling owing to the difficulty in working with membrane proteins.