Three-dimensional imaging reveals endo(sarco)plasmic reticulum-containing invaginations within the muscle nucleoplasm.

The mammalian nucleus has invaginations from the cytoplasm, termed nucleoplasmic reticulum (NR). With increased resolution of cellular imaging, progress has been made in understanding the formation and function of NR. In fact, nucleoplasmic Ca2+ homeostasis has been implicated in the regulation of gene expression, DNA repair, and cell death. However, the majority of studies focus on cross-sectional or single plane analyses of NR invaginations, providing an incomplete assessment of its distribution and content. Here, we provided advanced imaging and three-dimensional reconstructive analyses characterizing the molecular constituents of nuclear invaginations in the nucleoplasm in HEK293 cells, murine C2C12 muscle cells, and cardiac myocytes. We demonstrated the presence of critical Ca2+ regulatory channels including SERCA2a, STIM1, and ORAI1 in the nucleoplasm in isolated primary mouse cardiomyocytes. We have shown for the first time the presence of STIM1 and ORAI1 in the nucleoplasm, suggesting the presence of store-operated calcium entry (SOCE) mechanism in nucleoplasmic Ca2+ regulation. These results show that nucleoplasmic invaginations contain continuous ER components, mitochondria, and intact nuclear membranes, highlighting the extremely detailed and complex nature of this organellar structure. Copyright © 2017, American Journal of Physiology-Cell Physiology.

Citation

Shin-Haw Lee, Sina Hadipour-Lakmehsari, Tetsuaki Miyake, Anthony O Gramolini. Three-dimensional imaging reveals endo(sarco)plasmic reticulum-containing invaginations within the muscle nucleoplasm. American journal of physiology. Cell physiology. 2017 Nov 22:ajpcell.00141.2017

PMID: 29167149

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