Methionine sulfoxide reductase A regulates cell growth through the p53–p21 pathway

Microarray data analysis of antileukemic action of Cinnamoylated benzaldehyde LQB-461 in Jurkat cell line

BACKGROUND

Leukemias stand out for being the main type of childhood cancer in the world. Current treatments have strong side effects for patients, and there is still a high rate of development of resistance to multidrug therapy. Previously, our research group developed a structure-activity study with novel synthetic molecules analogous to LQB-278, described as an essential molecule with in vitro antileukemic action. Among these analogs, LQB-461 stood out, presenting more significant antileukemic action compared to its derivative LQB-278, with cytostatic and cytotoxicity effect by apoptosis, inducing caspase-3, and increased sub-G1 phase on cell cycle analysis.

METHODS AND RESULTS

Deepening the study of the mechanism of action of LQB-461 in Jurkat cells in vitro, a microarray assay was carried out, which confirmed the importance of the apoptosis pathway in the LQB-461 activity. Through real-time PCR, we validated an increased expression of CDKN1A and BAX genes, essential mediators of the apoptosis intrinsic pathway. Through the extrinsic apoptosis pathway, we found an increased expression of the Fas receptor by flow cytometry, showing the presence of a more sensitive population and another more resistant to death. Considering the importance of autophagy in cellular resistance, it was demonstrated by western blotting that LQB-461 decreased LC-3 protein expression, an autophagic marker.

CONCLUSIONS

These results suggest that this synthetic molecule LQB-461 induces cell death by apoptosis in Jurkat cells through intrinsic and extrinsic pathways and inhibits autophagy, overcoming some mechanisms of cell resistance related to this process, which differentiates LQB-461 of other drugs used for the leukemia treatment.

Methionine sulfoxide reductase A (MsrA) modulates cells and protects against Mycoplasma genitalium induced cytotoxicity

Methionine sulfoxide reductase A (MsrA) is a ubiquitous antioxidant repair enzyme which specifically reduces the oxidized methionine (Met-O) in proteins to methionine (Met). Previous studies have shown that lack of or overexpression of MsrA in cells affects the function of proteins and can lead to altered cellular processes. Interestingly, some pathogenic bacteria secrete and/or carry MsrA on their surface, suggesting some key roles for this enzyme in the modulation of host cellular processes. Therefore, we investigated how exogenously added MsrA affects the ability of the host cells in combating infection by using an in vitroMycoplasma genitalium cytotoxicity model. HeLa cells pretreated with MsrA and infected with M. genitalium showed significantly lower necrosis (cytotoxicity) than untreated cells infected with M. genitalium. Intriguingly, necrotic cell death pathway specific real time RT-PCR revealed that M. genitalium infection upregulates the expression of the TNF gene in HeLa cells and that MsrA pretreatment of the cells downregulates its expression significantly. Consistent with this, enzyme linked immunosorbent assay (ELISA) results showed that HeLa cells pretreated with MsrA secreted reduced levels of TNF-α following M. genitalium infection. Also, our study demonstrates that MsrA treatment of cells affects the phosphorylation status of transcriptional regulators such as NF-кB, JNK and p53 that regulate different cytokines. Further, fluorescent microscopy showed the cellular uptake of exogenously added MsrA fused with red fluorescent protein (MsrA-RFP). Altogether, our results suggest that secreted MsrA may help pathogens to modulate host cellular processes.

Methionine sulfoxide reductase (Msr) dysfunction in human brain disease

Extensive research has shown that oxidative stress is strongly associated with aging, senescence and several diseases, including neurodegenerative and psychiatric disorders. Oxidative stress is caused by the overproduction of reactive oxygen species (ROS) that can be counteracted by both enzymatic and nonenzymatic antioxidants. One of these antioxidant mechanisms is the widely studied methionine sulfoxide reductase system (Msr). Methionine is one of the most easily oxidized amino acids and Msr can reverse this oxidation and restore protein function, with MsrA and MsrB reducing different stereoisomers. This article focuses on experimental and genetic research performed on Msr and its link to brain diseases. Studies on several model systems as well as genome-wide association studies are compiled to highlight the role of MSRA in schizophrenia, Alzheimer's disease, and Parkinson's disease. Genetic variation of MSRA may also contribute to the risk of psychosis, personality traits, and metabolic factors.

Genetic regulation of longevity and age-associated diseases through the methionine sulfoxide reductase system

Methionine sulfoxide reductase enzymes are a protective system against biological oxidative stress in aerobic organisms. Modifications to this antioxidant system have been shown to impact the lifespan of several model system organisms. In humans, methionine oxidation of critical proteins and deficiencies in the methionine sulfoxide reductase system have been linked to age-related diseases, including cancer and neurodegenerative disease. Substrates for methionine sulfoxide reductases have been reviewed multiple times, and are still an active area of discovery. In contrast, less is known about the genetic regulation of methionine sulfoxide reductases. In this review, we discuss studies on the genetic regulation of the methionine sulfoxide reductase system with relevance to longevity and age-related diseases. A better understanding of genetic regulation for methionine sulfoxide reductases may lead to new therapeutic approaches for age-related diseases in the future.

MsrB3 deficiency induces cancer cell apoptosis through p53-independent and ER stress-dependent pathways

We have previously shown that down-regulation of methionine sulfoxide reductase B3 (MsrB3) induces cancer cell apoptosis through the activation of the intrinsic mitochondrial pathway. However, the mechanism through which MsrB3 deficiency results in cancer cell death is poorly understood. In this study, we investigated whether p53 and endoplasmic reticulum (ER) stress are involved in MsrB3 deficiency-induced cancer cell apoptosis using breast and colon cancer cells. MsrB3 depletion resulted in p53 down-regulation at the post-transcriptional level. MsrB3 deficiency induced cell death to a similar extent in both p53 wild-type (p53^+/+) and null (p53^-/-) cancer cells, suggesting that MsrB3 deficiency-induced apoptosis occurs independently of p53. MsrB3 deficiency significantly increased ER stress, which resulted in apoptosis. In addition, MsrB3 depletion activated the pro-apoptotic Bim molecule, which is essential for ER stress-induced apoptosis. MsrB3 deficiency increased cytosolic calcium levels, suggesting that MsrB3 down-regulation leads to a disturbance of calcium homeostasis in the ER, which consequently triggers ER stress. MsrB3 overexpression in MsrB3-depleted cells reduced ER stress, and was accompanied by at least partial recovery of cell viability. Taken together, our results suggest that MsrB3 plays a critical role in cancer cell apoptosis through the modulation of ER stress status.

Methionine sulfoxide reductase B3 deficiency stimulates heme oxygenase-1 expression via ROS-dependent and Nrf2 activation pathways

Methionine sulfoxide reductase B3 (MsrB3), which is primarily found in the endoplasmic reticulum (ER), is an important protein repair enzyme that stereospecifically reduces methionine-R-sulfoxide residues. We previously found that MsrB3 deficiency arrests the cell cycle at the G1/S stage through up-regulation of p21 and p27. In this study, we report a critical role of MsrB3 in gene expression of heme oxygenase-1 (HO-1), which has an anti-proliferative effect associated with p21 up-regulation. Depletion of MsrB3 elevated HO-1 expression in mammalian cells, whereas MsrB3 overexpression had no effect. MsrB3 deficiency increased cellular reactive oxygen species (ROS), particularly in the mitochondria. ER stress, which is associated with up-regulation of HO-1, was also induced by depletion of MsrB3. Treatment with N-acetylcysteine as an ROS scavenger reduced augmented HO-1 levels in MsrB3-depleted cells. MsrB3 deficiency activated Nrf2 transcription factor by enhancing its expression and nuclear import. The activation of Nrf2 induced by MsrB3 depletion was confirmed by increased expression levels of its other target genes, such as γ-glutamylcysteine ligase. Taken together, these data suggest that MsrB3 attenuates HO-1 induction by inhibiting ROS production, ER stress, and Nrf2 activation.

Deletion of Methionine Sulfoxide Reductase A Does Not Affect Atherothrombosis but Promotes Neointimal Hyperplasia and Extracellular Signal-Regulated Kinase 1/2 Signaling

OBJECTIVE

Emerging evidence suggests that methionine oxidation can directly affect protein function and may be linked to cardiovascular disease. The objective of this study was to define the role of the methionine sulfoxide reductase A (MsrA) in models of vascular disease and identify its signaling pathways.

APPROACH AND RESULTS

MsrA was readily identified in all layers of the vascular wall in human and murine arteries. Deletion of the MsrA gene did not affect atherosclerotic lesion area in apolipoprotein E-deficient mice and had no significant effect on susceptibility to experimental thrombosis after photochemical injury. In contrast, the neointimal area after vascular injury caused by complete ligation of the common carotid artery was significantly greater in MsrA-deficient than in control mice. In aortic vascular smooth muscle cells lacking MsrA, cell proliferation was significantly increased because of accelerated G1/S transition. In parallel, cyclin D1 protein and cdk4/cyclin D1 complex formation and activity were increased in MsrA-deficient vascular smooth muscle cell, leading to enhanced retinoblastoma protein phosphorylation and transcription of E2F. Finally, MsrA-deficient vascular smooth muscle cell exhibited greater activation of extracellular signal-regulated kinase 1/2 that was caused by increased activity of the Ras/Raf/mitogen-activated protein kinase signaling pathway.

CONCLUSIONS

Our findings implicate MsrA as a negative regulator of vascular smooth muscle cell proliferation and neointimal hyperplasia after vascular injury through control of the Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 signaling pathway.

The methionine sulfoxide reduction system: selenium utilization and methionine sulfoxide reductase enzymes and their functions

SIGNIFICANCE

Selenium is utilized in the methionine sulfoxide reduction system that occurs in most organisms. Methionine sulfoxide reductases (Msrs), MsrA and MsrB, are the enzymes responsible for this system. Msrs repair oxidatively damaged proteins, protect against oxidative stress, and regulate protein function, and have also been implicated in the aging process. Selenoprotein forms of Msrs containing selenocysteine (Sec) at the catalytic site are found in bacteria, algae, and animals.

RECENT ADVANCES

A selenoprotein MsrB1 knockout mouse has been developed. Significant progress in the biochemistry of Msrs has been made, which includes findings of a novel reducing system for Msrs and of an interesting reason for the use of Sec in the Msr system. The effects of mammalian MsrBs, including selenoprotein MsrB1 on fruit fly aging, have been investigated. Furthermore, it is evident that Msrs are involved in methionine metabolism and regulation of the trans-sulfuration pathway.

CRITICAL ISSUES

This article presents recent progress in the Msr field while focusing on the physiological roles of mammalian Msrs, functions of selenoprotein forms of Msrs, and their biochemistry.

FUTURE DIRECTIONS

A deeper understanding of the roles of Msrs in redox signaling, the aging process, and metabolism will be achieved. The identity of selenoproteome of Msrs will be sought along with characterization of the identified selenoprotein forms. Exploring new cellular targets and new functions of Msrs is also warranted.

Intersection of selenoproteins and kinase signalling

The small, obscure group of selenoprotein oxidoreductases and the huge clan of kinases, the workhorses of cellular signalling, are rarely discussed together. Focusing on selenoproteins of unknown structures, we predict a thioredoxin-like fold for the Selenoprotein N (SelN) family and use the structure to rationalise effects of the muscular myopathy-linked mutations in the gene coding SelN. Discussing the recent prediction of a protein kinase-like domain in the Selenoprotein O (SelO), we reiterate evidence for an oxidoreductase function alongside the predicted kinase domain. Thus, we propose that SelO, the strongly conserved kinase-cum-tentative-oxidoreductase may reflect oxidoreductase regulation of kinase networks. Also, we use bibliometric and systems biology approach to explore the kinase-selenoprotein relationships that begin to emerge from the literature. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).

Protein damage, repair and proteolysis

Proteins are continuously affected by various intrinsic and extrinsic factors. Damaged proteins influence several intracellular pathways and result in different disorders and diseases. Aggregation of damaged proteins depends on the balance between their generation and their reversal or elimination by protein repair systems and degradation, respectively. With regard to protein repair, only few repair mechanisms have been evidenced including the reduction of methionine sulfoxide residues by the methionine sulfoxide reductases, the conversion of isoaspartyl residues to L-aspartate by L-isoaspartate methyl transferase and deglycation by phosphorylation of protein-bound fructosamine by fructosamine-3-kinase. Protein degradation is orchestrated by two major proteolytic systems, namely the lysosome and the proteasome. Alteration of the function for both systems has been involved in all aspects of cellular metabolic networks linked to either normal or pathological processes. Given the importance of protein repair and degradation, great effort has recently been made regarding the modulation of these systems in various physiological conditions such as aging, as well as in diseases. Genetic modulation has produced promising results in the area of protein repair enzymes but there are not yet any identified potent inhibitors, and, to our knowledge, only one activating compound has been reported so far. In contrast, different drugs as well as natural compounds that interfere with proteolysis have been identified and/or developed resulting in homeostatic maintenance and/or the delay of disease progression.

Methionine sulfoxide reductase A attenuates heme oxygenase-1 induction through inhibition of Nrf2 activation

Methionine sulfoxide reductase A (MsrA) functions as a protein repair enzyme by catalyzing the stereospecific reduction of methionine-S-sulfoxide to methionine. We previously identified that MsrA deficiency inhibits normal cell growth via activation of the p53-p21 pathway. In this study, we report a critical role of MsrA in expression of heme oxygenase-1 (HO-1), a highly inducible enzyme that has an anti-proliferative effect mediated by up-regulation of p21. Down-regulation of MsrA induced HO-1 expression in mammalian cells with increased p21 levels, but MsrA overexpression did not affect HO-1 expression. MsrA depletion activated Nrf2 by increasing its expression and nuclear translocation. Nrf2 activation was associated with increased reactive oxygen species production. MsrA overexpression in MsrA-depleted cells led to the reduction of increased HO-1 expression, and suppressed nuclear accumulation of Nrf2. Taken together, the data suggest that MsrA attenuates HO-1 induction by inhibiting Nrf2 activation.

Methionine sulfoxide reductase B3 protects from endoplasmic reticulum stress in Drosophila and in mammalian cells

Methionine sulfoxide reductase B3A (MsrB3A), which catalyzes the stereospecific reduction of methionine-R-sulfoxide to methionine, is localized to the endoplasmic reticulum (ER). Here, we report a critical role of the ER-targeted MsrB3 in protection against ER stress in Drosophila and in mammalian cells. Flies overexpressing human MsrB3A exhibited significantly increased resistance to ER stress induced by dithiothreitol. These flies also showed slightly enhanced resistance to tunicamycin-induced ER stress. In addition, overexpression of MsrB3A in mammalian cells increased resistance to dithiothreitol- and thapsigargin-induced ER stresses. However, MsrB3A overexpression had no effect on the resistance to tunicamycin-induced ER stress. Knockdown of MsrB3A in mammalian cells led to a significant decrease in the resistance to thapsigargin-induced ER stress, but had no effects on the resistance to either dithiothreitol- or tunicamycin-induced ER stress. Collectively, our data provide evidence that the ER-type of MsrB3 plays an important role in protection against ER stress, suggesting that MsrB3 may be involved in the regulation of ER homeostasis.