National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM093271
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R01GM111367
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R21GM131231
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
U24GM116788
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
U24GM116789
United States
National Institutes of Health/National Cancer Institute (NIH/NCI)
C06RR30414
United States
National Institutes of Health/National Cancer Institute (NIH/NCI)
U24GM129539
United States
Cancer Prevention and Research Institute of Texas (CPRIT)
RP120474
United States
American Heart Association
12IRG9400019
United States
National Institutes of Health/National Cancer Institute (NIH/NCI)
R01GM088745
United States
Cystic Fibrosis Foundation
JIANG15G0
United States
Welch Foundation
I-1684
United States
Citation
Journal: Front Mol Neurosci / Year: 2023 Title: Chromogranin B (CHGB) is dimorphic and responsible for dominant anion channels delivered to cell surface via regulated secretion. Authors: Gaya P Yadav / Haiyuan Wang / Joke Ouwendijk / Stephen Cross / Qiaochu Wang / Feng Qin / Paul Verkade / Michael X Zhu / Qiu-Xing Jiang / Abstract: Regulated secretion is conserved in all eukaryotes. In vertebrates granin family proteins function in all key steps of regulated secretion. Phase separation and amyloid-based storage of proteins and ...Regulated secretion is conserved in all eukaryotes. In vertebrates granin family proteins function in all key steps of regulated secretion. Phase separation and amyloid-based storage of proteins and small molecules in secretory granules require ion homeostasis to maintain their steady states, and thus need ion conductances in granule membranes. But granular ion channels are still elusive. Here we show that granule exocytosis in neuroendocrine cells delivers to cell surface dominant anion channels, to which chromogranin B (CHGB) is critical. Biochemical fractionation shows that native CHGB distributes nearly equally in soluble and membrane-bound forms, and both reconstitute highly selective anion channels in membrane. Confocal imaging resolves granular membrane components including proton pumps and CHGB in puncta on the cell surface after stimulated exocytosis. High pressure freezing immuno-EM reveals a major fraction of CHGB at granule membranes in rat pancreatic β-cells. A cryo-EM structure of bCHGB dimer of a nominal 3.5 Å resolution delineates a central pore with end openings, physically sufficient for membrane-spanning and large single channel conductance. Together our data support that CHGB-containing (CHGB+) channels are characteristic of regulated secretion, and function in granule ion homeostasis near the plasma membrane or possibly in other intracellular processes.
Type of model: OTHER Details: Ab initio model from cisTEM and cryoSPARC, and a reference model from angular reconstitution of a negative stain dataset.
Final reconstruction
Applied symmetry - Point group: C2 (2 fold cyclic) / Resolution.type: BY AUTHOR / Resolution: 3.5 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. 3.3.2) Details: CryoSPARC and relion were used for independent analyses to generate similar results. Number images used: 70000
Initial angle assignment
Type: MAXIMUM LIKELIHOOD Details: Initial assignment was based on the reference model.
Final angle assignment
Type: MAXIMUM LIKELIHOOD Details: Refinement was done in cryoSPARC and relion separately.
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