Cell Invasion by Neisseria meningitidis Requires a Functional Interplay between the Focal Adhesion Kinase, Src and Cortactin

Entry of Neisseria meningitidis (the meningococcus) into human brain microvascular endothelial cells (HBMEC) is mediated by fibronectin or vitronectin bound to the surface protein Opc forming a bridge to the respective integrins. This interaction leads to cytoskeletal rearrangement and uptake of meningococci. In this study, we determined that the focal adhesion kinase (FAK), which directly associates with integrins, is involved in integrin-mediated internalization of N. meningitidis in HBMEC. Inhibition of FAK activity by the specific FAK inhibitor PF 573882 reduced Opc-mediated invasion of HBMEC more than 90%. Moreover, overexpression of FAK mutants that were either impaired in the kinase activity or were not capable of autophosphorylation or overexpression of the dominant-negative version of FAK (FRNK) blocked integrin-mediated internalization of N. meningitidis. Importantly, FAK-deficient fibroblasts were significantly less invaded by N. meningitidis. Furthermore, N. meningitidis induced tyrosine phosphorylation of several host proteins including the FAK/Src complex substrate cortactin. Inhibition of cortactin expression by siRNA silencing and mutation of critical amino acid residues within cortactin, that encompass Arp2/3 association and dynamin binding, significantly reduced meningococcal invasion into eukaryotic cells suggesting that both domains are critical for efficient uptake of N. meningitidis into eukaryotic cells. Together, these results indicate that N. meningitidis exploits the integrin signal pathway for its entry and that FAK mediates the transfer of signals from activated integrins to the cytoskeleton. A cooperative interplay between FAK, Src and cortactin then enables endocytosis of N. meningitidis into host cells

Simulation of maneuvering aircraft

Within the DLR-Project SikMa-„Simulation komplexer Manöver“ („Simulation of Complex Maneuvers“) the development of a numerical simulation framework for calculating a free flying aeroelastic manoeuvring combat aircraft is realised. To achieve this objective a multidisciplinary time accurate coupling of computational codes is done. The computational aerodynamic, structural and flight mechanic codes are embedded into an interactive simulation environment in which the coupling, data transfer, pre- and post-processing is done. On the CFD side the DLR TAU-Code is used to predict the unsteady aerodynamics. During the last year several project specific changes have been implemented in the TAU-Code. For calculating a fully equipped X-31, and coupling with the other disciplines, the handling of multi-body configurations and resulting motion definitions had to be enhanced, with regards to both the data exchange interface and the parallelization of the ADT search algorithm for the chimera overset grid technique. In order to calculate the deformation of the aircraft a CSM-Code is implemented in the simulation environment. The CSM-Code uses the full mass- and stiffness matrices of the given finite-element model, and has several interpolation routines for data-transfer between CFD and FEM grids; time-integration is done using an implicit Newmark algorithm. The DLR flight-mechanic library SIMULA is used to determine the flight trajectory of the free-flying, maneuvering aircraft. Wind tunnel experiments are provided in order to validate the simulation environment. The model used for the experiments is the X-31 configuration. The X-31 wind tunnel model is depicted in Fig. 1. The time accurate maneuver simulation of the X-31 will be shown. The simulation will start with the determination of a trim condition and than a maneuver due to control device deflectionwill be initiated. In a second simulation the structural mechanics behavior of the aircraft is also taken into account