RESUMO
Genetically encoded FRET based biosensors allow one to visualize the spatial and temporal evolution of specific enzyme activities in live cells. We have previously reported the creation of a FRET based biosensor specific for Zeta-Associated Protein -70 kD (ZAP-70) (Randriamampita et al., 2008), a Syk family protein tyrosine kinase. ZAP-70 is essential for early T cell receptor (TCR) signaling events, T lymphocyte development and has also been implicated in integrin mediated T lymphocyte migration. In order to facilitate the study of ZAP-70 kinase activity during dynamic phenomena such as immunological synapse formation or cell migration, we have designed and prepared a second generation of ZAP-70 specific biosensors. Here we describe a novel biosensor named ROZA-XL, that displays a 3-4 times greater dynamic range than its predecessor and possesses a robust baseline FRET value when expressed in the Jurkat human T cell line. We demonstrate that the robust behavior of this biosensor allows for rapid analysis of TCR mediated of ZAP-70 kinase activity at a single cell level, as shown in a simple end point assay in which ROZA-XL expressing cells are allowed to interact with stimulatory anti-CD3epsilon coated coverslips.
Assuntos
Técnicas Biossensoriais/métodos , Transferência Ressonante de Energia de Fluorescência/métodos , Linfócitos T/enzimologia , Proteína-Tirosina Quinase ZAP-70/metabolismo , Sequência de Aminoácidos , Corantes Fluorescentes/química , Humanos , Células Jurkat , Proteínas Luminescentes/química , Proteínas Luminescentes/genética , Dados de Sequência Molecular , Receptores de Antígenos de Linfócitos T/metabolismo , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Transdução de Sinais , Análise de Célula Única/métodos , Linfócitos T/imunologiaRESUMO
As they leave the blood stream and travel to lymph nodes or sites of inflammation, T lymphocytes are captured by the endothelium and migrate along the vascular wall to permissive sites of transmigration. These processes take place under the influence of hemodynamic shear stress; therefore, we investigated how migrational speed and directionality are influenced by variations in shear stress. We examined human effector T lymphocytes on intercellular adhesion molecule 1 (ICAM-1)-coated surfaces under the influence of shear stresses from 2 to 60 dyn.cm(-2). T lymphocytes were shown to respond to shear stress application by a rapid (30 s) and fully reversible orientation of their migration against the fluid flow without a change in migration speed. Primary T lymphocytes migrating on ICAM-1 in the presence of uniformly applied SDF-1α were also found to migrate against the direction of shear flow. In sharp contrast, neutrophils migrating in the presence of uniformly applied fMLP and leukemic HSB2 T lymphocytes migrating on ICAM-1 alone oriented their migration downstream, with the direction of fluid flow. Our findings suggest that, in addition to biochemical cues, shear stress is a contributing factor to leukocyte migration directionality.
