title: Nanoscale distribution of ryanodine receptors and caveolin-3 in mouse ventricular myocytes: dilation of t-tubules near junctions.
abstract: We conducted super-resolution light microscopy (LM) imaging of the distribution of ryanodine receptors (RyRs) and caveolin-3 (CAV3) in mouse ventricular myocytes. Quantitative analysis of data at the surface sarcolemma showed that 4.8% of RyR labeling colocalized with CAV3 whereas 3.5% of CAV3 was in areas with RyR labeling. These values increased to 9.2 and 9.0%, respectively, in the interior of myocytes where CAV3 was widely expressed in the t-system but reduced in regions associated with junctional couplings. Electron microscopic (EM) tomography independently showed only few couplings with caveolae and little evidence for caveolar shapes on the t-system. Unexpectedly, both super-resolution LM and three-dimensional EM data (including serial block-face scanning EM) revealed significant increases in local t-system diameters in many regions associated with junctions. We suggest that this regional specialization helps reduce ionic accumulation and depletion in t-system lumen during excitation-contraction coupling to ensure effective local Ca²⁺ release. Our data demonstrate that super-resolution LM and volume EM techniques complementarily enhance information on subcellular structure at the nanoscale.
authors.affiliation: Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Wong
authors.forename: David
authors.initials: D
authors.lastname: Baddeley
authors.forename: Eric A
authors.initials: EA
authors.lastname: Bushong
authors.forename: Zeyun
authors.initials: Z
authors.lastname: Yu
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ellisman
authors.forename: Masahiko
authors.initials: M
authors.lastname: Hoshijima
authors.forename: Christian
authors.initials: C
authors.lastname: Soeller
mesh_terms: D000818:Animals; D051244:Caveolin 3 / Q000737:chemistry* / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology*; D051379:Mice; D008856:Microscopy, Fluorescence; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D049329:Nanostructures; D021381:Protein Transport; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D051244:Caveolin 3; D019837:Ryanodine Receptor Calcium Release Channel