InstructThe latest webinar in the Instruct-ERIC Structure Meets Function series was hosted by Instruct-CZ. Register for the webinar here.
The webinar will took place 11:00 CET, on 14 March.
Featuring expert speakers from Instruct Centres across Europe, Instruct-ERIC Webinar Series: Structure Meets Function highlights some of the latest developments in structural biology, demonstrating how integrative methods are enabling scientists to decipher the mechanisms that underpin health and disease.
Take a look at the previous webinars in the series here.
Moderator: Jan Dohnalek
Talk 1: Structure of tick-borne encephalitis virus immature particle solved by cryo-electron microscopy and sub-tomogram averaging
Speaker: Tibor Fuzik
Abstract: Tick-borne encephalitis virus (TBEV) is an enveloped virus belonging to the family Flaviviridae. It is mainly transmitted by ticks and causes severe disease of central nervous system in humans. Virion surface is covered by envelope proteins (E-protein), that are together with the membrane proteins (M-protein) anchored in the virus lipid bilayer. During the viral life cycle, the immature non-infectious virus undergoes a maturation process. This process includes proteolytic cleavage of prM and major reorganization of the envelope proteins on the viral surface. To determine the structure of immature TBEV particles, we purified them from infected tissue culture cells and used cryo-electron microscopy for visualization.
In comparison with smooth mature TBEV particles, the immature particles have “spiky” surface formed by the E-protein-prM-protein complex. We combined cryo-electron tomography and sub-tomogram averaging with single-particle analysis methods using localized reconstruction of the surface “spikes”, to determine the high-resolution structure of the immature E-protein complexes and their interaction with the prM-protein. The organization of the particle surface indicates that the TBEV maturation mechanism involves a complex reorganization of the envelope proteins on the viral surface.
The results show more detailed insight in the viral maturation process which may be targeted by specific antiviral drugs.
Talk 2: Structure of the human NK cell NKR-P1:LLT1 receptor:ligand complex reveals clustering in the immune synapse
Speaker: Ondrej Vanek
Abstract: Natural killer (NK) cells are innate immune lymphocytes equipped with a wide range of activating and inhibitory surface receptors, allowing them to sensitively recognize and kill malignant, infected, or other transformed cells through “missing-“ and “induced-self” mechanisms and through antibody-dependent cell-mediated cytotoxicity.
Signaling by the human C-type lectin-like receptor, natural killer (NK) cell inhibitory receptor NKR-P1, has a critical role in many immune-related diseases and cancer. C-type lectin-like receptors have weak affinities to their ligands; therefore, setting up a comprehensive model of NKR-P1-LLT1 interactions that considers the natural state of the receptor on the cell surface is necessary to understand its functions. Here we report the crystal structures of the NKR-P1 and NKR-P1:LLT1 complexes, which provides evidence that NKR-P1 forms homodimers in an unexpected arrangement to enable LLT1 binding in two modes, bridging two LLT1 molecules.
These interaction clusters are suggestive of an inhibitory immune synapse. By observing the formation of these clusters in solution using SEC-SAXS analysis, by dSTORM super-resolution microscopy on the cell surface, and by following their role in receptor signaling with freshly isolated NK cells, we show that only the ligation of both LLT1 binding interfaces leads to effective NKR-P1 inhibitory signaling.
In summary, our findings collectively support a model of NKR-P1:LLT1 clustering, which allows the interacting proteins to overcome weak ligand-receptor affinity and to trigger signal transduction upon cellular contact in the immune synapse, thereby providing a good model for the future description of related homologous low-affinity complexes.
