Structural insights into Ca2+-activated long-range allosteric channel gating of RyR1

Ryanodine receptors (RyRs) are a class of giant ion channels with molecular mass over 2.2 mega-Daltons. These channels mediate calcium signaling in a variety of cells. Since more than 80% of the RyR protein is folded into the cytoplasmic assembly and the remaining residues form the transmembrane domain, it has been hypothesized that the activation and regulation of RyR channels occur through an as yet uncharacterized long-range allosteric mechanism. Here we report the characterization of a Ca2+-activated open-state RyR1 structure by cryo-electron microscopy. The structure has an overall resolution of 4.9 angstrom and a resolution of 4.2 angstrom for the core region. In comparison with the previously determined apo/closed-state structure, we observed long-range allosteric gating of the channel upon Ca2+ activation. In-depth structural analyses elucidated a novel channel-gating mechanism and a novel ion selectivity mechanism of RyR1. Our work not only provides structural insights into the molecular mechanisms of channel gating and regulation of RyRs, but also sheds light on structural basis for channel-gating and ion selectivity mechanisms for the six-transmembrane-helix cation channel family.Strategic Priority Research Program of Chinese Academy of Sciences [XDB08030202]; National Basic Research Program (973 Program); Ministry of Science & Technology of China [2012CB917200, 2014CB910700]; National Natural Science Foundation of China [31270768]; Ministry of Education of China (111 Program China)SCI(E)PubMed中国科技核心期刊(ISTIC)[email protected]; [email protected]

Benchtop and Animal Validation of a Projective Imaging System for Potential Use in Intraoperative Surgical Guidance

<div><p>We propose a projective navigation system for fluorescence imaging and image display in a natural mode of visual perception. The system consists of an excitation light source, a monochromatic charge coupled device (CCD) camera, a host computer, a projector, a proximity sensor and a Complementary metal–oxide–semiconductor (CMOS) camera. With perspective transformation and calibration, our surgical navigation system is able to achieve an overall imaging speed higher than 60 frames per second, with a latency of 330 ms, a spatial sensitivity better than 0.5 mm in both vertical and horizontal directions, and a projection bias less than 1 mm. The technical feasibility of image-guided surgery is demonstrated in both agar-agar gel phantoms and an ex vivo chicken breast model embedding Indocyanine Green (ICG). The biological utility of the system is demonstrated in vivo in a classic model of ICG hepatic metabolism. Our benchtop, ex vivo and in vivo experiments demonstrate the clinical potential for intraoperative delineation of disease margin and image-guided resection surgery.</p></div

Fluorescence imaging projective surgical navigation system.

<p>(a) Schematic diagram of the projective surgical navigation system; (b) Projective surgical navigation system in working mode.</p

In vivo, ICG concentration–time course in mouse liver following ICG injection.

<p>(a) The nude mouse before dissection at 3 hours after ICG tail intravenous injection; (b) After the mouse is sacrificed by cervical vertebra dislocation, we dissect its abdomen and observe the anatomy map. (c) The fluorescence image captured by NIR camera. The area into the white frame is used to calculate fluorescence intensity. (d)The image of nude mouse under projective navigation system captured by nude eye. (e) Corresponding fluorescence intensity basis time courses.</p

Phantom study to show the projective accuracy as the function of the height difference between the projection plane and the reference plane.

<p>(a)—(e): As the projection plane moves from 40 mm above to 40 mm below the registered reference plane, the projected image is biased from left to the right of the actual phantom. (c): If the projection plane is identical to the reference plane, the projected image and the actual phantom are co-registered without bias. (f) Linear relationship is observed between the projection bias and the height difference without height correction, while the projection bias is controlled within 1 mm for all the height differences after the height correction algorithm is applied.</p

The relationship between projection bias and height difference.

<p>(a) Schematic diagram of the projection bias induced by height variation after registration, plane α is the registration plane and there is a bias l on the observation plane β; (b) The triangle caused deviation in (a).</p

Comparison of the projective system with other NIFR systems.

<p>Comparison of the projective system with other NIFR systems.</p