Northwestern大学医学系大学院 Steve H. DeVries教授によるセミナーが開催されました。
2021年3月22日お知らせ
Northwestern大学医学系大学院 Steve H. DeVries教授によるセミナーが開催されました。
開催日：2021年2月25日（木）14：00～15:30
場所 ：オンライン（Zoom、Youtube）
演者 ：Northwestern大学医学系大学院 Steve H. DeVries教授 Depts of Ophthalmology & Physiology
タイトル：Design of the mammalian cone photoreceptor synapse
要旨：The cone photoreceptor synapse is an essential link in daylight vision. At the synapse, a time-varying change in cone membrane voltage, the light response, modulates the rate of vesicle fusion at ~20 discrete ribbon sites, producing a spatiotemporal glutamate gradient in the cleft. This gradient is sampled by the dendritic processes of more than a dozen types of cone bipolar cells, creating separate voltage signals that provide the raw material for downstream processing. Under steady voltage conditions, the release rate at each ribbon fluctuates around a mean value, and thus, for a bipolar cell type, the best estimate of the cone signal should be obtained by averaging release from all of a cone’s ribbons. Deviations from a maximal sampling strategy may reflect space limitations at the synapse or may indicate an alternative sampling strategy. We focus on the Off bipolar cells, which express ionotropic glutamate receptors. Sampling is measured during paired recordings by comparing the number of quanta released by a cone to the number simultaneously detected by an identified postsynaptic bipolar cell type. Additional structural and mechanistic information is obtained by visualizing the synapse with 3D-STED super-resolution microscopy, via rapid agonist perfusion of postsynaptic receptors, and by Monte Carlo (MCell) simulation. We find that Off bipolar cells can be divided into 3 groups based on sampling strategy. Two groups sample most or all ribbon sites but at different locations relative to those sites, invaginating and basal. The third group uses a different sampling strategy. Bipolar cells in this group express a low affinity glutamate receptor and make a small number of contacts at the center of the cone terminal base. These contacts respond preferentially during strong release where the glutamate gradients from neighboring sites overlap and merge. Preliminary data from transcriptomic and proteomic approaches suggest a basis for sampling diversity.
