title: Real-time quantitative measurement of autocrine ligand binding indicates that autocrine loops are spatially localized.
abstract: Autocrine ligands are important regulators of many normal tissues and have been implicated in a number of disease states, including cancer. However, because by definition autocrine ligands are synthesized, secreted, and bound to cell receptors within an intrinsically self-contained "loop," standard pharmacological approaches cannot be used to investigate relationships between ligand/receptor binding and consequent cellular responses. We demonstrate here a new approach for measurement of autocrine ligand binding to cells, using a microphysiometer assay originally developed for investigating cell responses to exogenous ligands. This technique permits quantitative measurements of autocrine responses on the time scale of receptor binding and internalization, thus allowing investigation of the role of receptor trafficking and dynamics in cellular responses. We used this technique to investigate autocrine signaling through the epidermal growth factor receptor by transforming growth factor alpha (TGFalpha) and found that anti-receptor antibodies are far more effective than anti-ligand antibodies in inhibiting autocrine signaling. This result indicates that autocrine-based signals can operate in a spatially restricted, local manner and thus provide cells with information on their local microenvironment.
authors.affiliation: Division of Bioengineering & Environmental Health and Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. lauffen@mit.edu
authors.forename: D A
authors.initials: DA
authors.lastname: Lauffenburger
authors.forename: G T
authors.initials: GT
authors.lastname: Oehrtman
authors.forename: L
authors.initials: L
authors.lastname: Walker
authors.forename: H S
authors.initials: HS
authors.lastname: Wiley
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007700:Kinetics; D008024:Ligands; D051379:Mice; D011869:Radioligand Assay; D015398:Signal Transduction; D013997:Time Factors; D016211:Transforming Growth Factor alpha / Q000494:pharmacology / Q000502:physiology
chemical_list: D007457:Iodine Radioisotopes; D008024:Ligands; D016211:Transforming Growth Factor alpha; D004815:Epidermal Growth Factor; D066246:ErbB Receptors