Inhibition of protein synthesis by nitric oxide correlates with cytostatic activity: nitric oxide induces phosphorylation of initiation factor eIF-2 alpha.
نویسندگان
چکیده
BACKGROUND Nitric oxide (NO) is cytostatic for proliferating cells, inhibits microbial growth, and down-regulates the synthesis of specific proteins. Studies were undertaken to determine the mechanism by which NO inhibits total protein synthesis and whether the inhibition correlates with established cytostatic activities of NO. MATERIALS AND METHODS In in vitro experiments, various cell types were exposed to NO using either donors or expression of inducible NO synthase (iNOS). The capacity of NO to suppress total protein synthesis, measured by incorporation of 35S-methionine into protein, was correlated with the capacity of NO to suppress cell proliferation, viral replication, or iNOS expression. Phosphorylation of eIF-2 alpha was examined as a possible mechanism for the suppressed protein synthesis by NO. RESULTS Both NO donors and expression of the iNOS suppressed total protein synthesis in L929 cells and A2008 human ovarian tumor cells in parallel with decreased cell proliferation. Suppressed protein synthesis was also shown to correlate with decreased vaccinia virus proliferation in murine peritoneal macrophages in an iNOS-dependent manner. Furthermore, iNOS expression in pancreatic islets or RAW264.7 cells almost completely inhibited total protein synthesis, suggesting that nonspecific inhibition of protein synthesis may be the mechanism by which NO inhibited the synthesis of specific proteins such as insulin or iNOS itself. This possibility was confirmed in RAW264.7 cells where the inhibition of total protein synthesis correlated with the decreased iNOS protein. The decrease in protein levels occurred without changes in iNOS mRNA levels, implicating an inhibition of translation. Mechanistic studies revealed that iNOS expression in RAW264.7 cells resulted in the phosphorylation of eIF-2 alpha and inhibition of the 80S ribosomal complex formation. CONCLUSIONS These results suggest that NO suppresses protein synthesis by stimulating the phosphorylation of eIF-2 alpha. Furthermore, our observations indicate that nonspecific inhibition of protein synthesis may be a generalized response of cells exposed to high levels of NO and that inhibition of protein synthesis may contribute to many of the described cytostatic actions of NO.
منابع مشابه
Nitric oxide mediates NMDA-induced persistent inhibition of protein synthesis through dephosphorylation of eukaryotic initiation factor 4E-binding protein 1 and eukaryotic initiation factor 4G proteolysis.
Cerebral ischaemia causes long-lasting protein synthesis inhibition that is believed to contribute to brain damage. Energy depletion promotes translation inhibition during ischaemia, and the phosphorylation of eIF (eukaryotic initiation factor) 2alpha is involved in the translation inhibition induced by early ischaemia/reperfusion. However, the molecular mechanisms underlying prolonged translat...
متن کاملThe Role of Nitric Oxide Synthase in the Regulation of Ultraviolet Light-induced Phosphorylation
Ultraviolet light (UV) induces phosphorylation of the alpha subunit of the eukaryotic initiation factor 2 (eIF2α) and inhibits global protein synthesis. Both eIF2 kinases, PERK and GCN2, have been shown to phosphorylate eIF2α in response to UV-irradiation. However, the roles of PERK and GCN2 in UV-induced eIF2α phosphorylation are controversial. The upstream signaling pathway(s) that leads to t...
متن کاملDetermination of Optimum Conditions for the Production of Peptides with Antioxidant and Nitric-Oxide Inhibition Properties from Protein Hydrolysis of Pumpkin Seed Meals Using Pepsin Enzyme
Background and Objectives: In this study, hydrolysis condition optimization of the pumpkin (Cucurbita pepo) seed proteins was carried out achieve maximum DPPH radical scavenging and nitric-oxide inhibition properties using Design Expert Software and response surface methodology. Materials & Methods: In general, 1–3% concentrations of pepsin enzyme, 30–40 °C temperature and 120–100 min time we...
متن کاملNectandrin B activates endothelial nitric-oxide synthase phosphorylation in endothelial cells: role of the AMP-activated protein kinase/estrogen receptor α/phosphatidylinositol 3-kinase/Akt pathway.
We revealed previously that nectandrin B isolated from Myristica fragrans (nutmeg, Myristicaceae) functions as a potent AMP-activated protein kinase (AMPK) activator and showed its antiobesity effect. In this study, we investigated whether nectandrin B affects phosphorylation of endothelial nitric-oxide synthase (eNOS) in human endothelial cells. Nectandrin B increased the phosphorylation of eN...
متن کاملCrocin Suppresses LPS-Stimulated Expression of Inducible Nitric Oxide Synthase by Upregulation of Heme Oxygenase-1 via Calcium/Calmodulin-Dependent Protein Kinase 4
Crocin is a water-soluble carotenoid pigment that is primarily used in various cuisines as a seasoning and coloring agent, as well as in traditional medicines for the treatment of edema, fever, and hepatic disorder. In this study, we demonstrated that crocin markedly induces the expression of heme oxygenase-1 (HO-1) which leads to an anti-inflammatory response. Crocin inhibited inducible nitric...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Molecular medicine
دوره 4 3 شماره
صفحات -
تاریخ انتشار 1998