Active nNOS Is Required for Grp94-Induced Antioxidant Cytoprotection: A Lesson from Myogenic to Cancer Cells
The endoplasmic reticulum (ER) chaperone Grp94/gp96 appears to be involved in cytoprotection without being required for cell survival. This study compared the effects of Grp94 protein levels on Ca<sup>2+</sup> homeostasis, antioxidant cytoprotection and protein–protein interactions betwe...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-03-01
|
| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/23/6/2915 |
| Summary: | The endoplasmic reticulum (ER) chaperone Grp94/gp96 appears to be involved in cytoprotection without being required for cell survival. This study compared the effects of Grp94 protein levels on Ca<sup>2+</sup> homeostasis, antioxidant cytoprotection and protein–protein interactions between two widely studied cell lines, the myogenic C2C12 and the epithelial HeLa, and two breast cancer cell lines, MDA-MB-231 and HS578T. In myogenic cells, but not in HeLa, Grp94 overexpression exerted cytoprotection by reducing ER Ca<sup>2+</sup> storage, due to an inhibitory effect on SERCA2. In C2C12 cells, but not in HeLa, Grp94 co-immunoprecipitated with non-client proteins, such as nNOS, SERCA2 and PMCA, which co-fractionated by sucrose gradient centrifugation in a distinct, medium density, ER vesicular compartment. Active nNOS was also required for Grp94-induced cytoprotection, since its inhibition by L-NNA disrupted the co-immunoprecipitation and co-fractionation of Grp94 with nNOS and SERCA2, and increased apoptosis. Comparably, only the breast cancer cell line MDA-MB-231, which showed Grp94 co-immunoprecipitation with nNOS, SERCA2 and PMCA, increased oxidant-induced apoptosis after nNOS inhibition or Grp94 silencing. These results identify the Grp94-driven multiprotein complex, including active nNOS as mechanistically involved in antioxidant cytoprotection by means of nNOS activity and improved Ca<sup>2+</sup> homeostasis. |
|---|---|
| ISSN: | 1661-6596 1422-0067 |