title: Phosphotyrosine-mediated LAT assembly on membranes drives kinetic bifurcation in recruitment dynamics of the Ras activator SOS.
abstract: The assembly of cell surface receptors with downstream signaling molecules is a commonly occurring theme in multiple signaling systems. However, little is known about how these assemblies modulate reaction kinetics and the ultimate propagation of signals. Here, we reconstitute phosphotyrosine-mediated assembly of extended linker for the activation of T cells (LAT):growth factor receptor-bound protein 2 (Grb2):Son of Sevenless (SOS) networks, derived from the T-cell receptor signaling system, on supported membranes. Single-molecule dwell time distributions reveal two, well-differentiated kinetic species for both Grb2 and SOS on the LAT assemblies. The majority fraction of membrane-recruited Grb2 and SOS both exhibit fast kinetics and single exponential dwell time distributions, with average dwell times of hundreds of milliseconds. The minor fraction exhibits much slower kinetics, extending the dwell times to tens of seconds. Considering this result in the context of the multistep process by which the Ras GEF (guanine nucleotide exchange factor) activity of SOS is activated indicates that kinetic stabilization from the LAT assembly may be important. This kinetic proofreading effect would additionally serve as a stochastic noise filter by reducing the relative probability of spontaneous SOS activation in the absence of receptor triggering. The generality of receptor-mediated assembly suggests that such effects may play a role in multiple receptor proximal signaling processes.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: William Y C
authors.initials: WY
authors.lastname: Huang
authors.affiliation: Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
authors.forename: Qingrong
authors.initials: Q
authors.lastname: Yan
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Wan-Chen
authors.initials: WC
authors.lastname: Lin
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Jean K
authors.initials: JK
authors.lastname: Chung
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Scott D
authors.initials: SD
authors.lastname: Hansen
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Sune M
authors.initials: SM
authors.lastname: Christensen
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720;
authors.forename: Hsiung-Lin
authors.initials: HL
authors.lastname: Tu
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720.
authors.forename: John
authors.initials: J
authors.lastname: Kuriyan
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720; jtgroves@lbl.gov.
authors.forename: Jay T
authors.initials: JT
authors.lastname: Groves
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008567:Membranes, Artificial; D019000:Phosphotyrosine / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D015398:Signal Transduction; D020664:Son of Sevenless Proteins / Q000378:metabolism*; D018631:ras Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C110810:LAT protein, human; D008565:Membrane Proteins; D008567:Membranes, Artificial; D011948:Receptors, Antigen, T-Cell; D020664:Son of Sevenless Proteins; D019000:Phosphotyrosine; D018631:ras Proteins
keywords: kinetic proofreading; membrane dwell time; protein assembly; signal transduction; single molecule