title: In situ visualizing T-Tubule/SR junction reveals the ultra-structures of calcium storage and release machinery.
abstract: In skeletal muscle, Ca(2+) release from sarcoplasmic reticulum (SR) following the action potential relies on the delicate architecture of the T-Tubule/SR junction. The T-Tubule/SR junction comprises two membrane systems: the integral proteins DHPR and RyR1 and the Ca(2+)-buffering apparatus within the SR lumen. The arrangement and interactions of the components have remained elusive due to technological limitations. Here, we determined whether electron tomography is effective fort the in situ determination of the relationships between RyR1 and DHPR, the SR membrane and other involved structures. First, we visually confirmed that RyR1 and DHPR are close neighbors that are mutually staggered with each other and directly interact with one of RyR1 subunits. Second, the Ca(2+) storage network within the SR lumen is directly correlated with RyR1. These results suggest that the excitation of the T-Tubule may induce Ca(2+) release through a direct interaction among DHPR, RyR1 and the Ca(2+) buffering apparatus. These results indicate that electron tomography has potential as an efficient method for the in situ characterization of the complex architecture and arrangement of two integral-integral-membrane proteins in the context of the surrounding phospholipid-bilayer and proteins.
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China.
authors.forename: XiaoWei
authors.initials: X
authors.lastname: Song
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China.
authors.forename: ChangHai
authors.initials: C
authors.lastname: Lei
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China.
authors.forename: Mi
authors.initials: M
authors.lastname: Cao
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China.
authors.forename: YaFeng
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Biophysics, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China. Electronic address: yangyj22@smmu.edu.cn.
authors.forename: YongJi
authors.initials: Y
authors.lastname: Yang
mesh_terms: D000818:Animals; D001001:Anura; D002118:Calcium / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium
keywords: DHPR; Electron tomography; Integral–integral-membrane proteins; Macromolecular architecture; RyR1