SOD2

Superoxide dismutase 2, mitochondrial

PDB rendering based on 1ap5.
Available structures
PDB Ortholog search: PDBe, RCSB
Identifiers
Symbols SOD2 ; IPOB; MNSOD; MVCD6
External IDs OMIM: 147460 MGI: 98352 HomoloGene: 530 GeneCards: SOD2 Gene
EC number 1.15.1.1
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 6648 20656
Ensembl ENSG00000112096 ENSMUSG00000006818
UniProt P04179 P09671
RefSeq (mRNA) NM_000636 NM_013671
RefSeq (protein) NP_000627 NP_038699
Location (UCSC) Chr 6:
159.67 – 159.76 Mb		 Chr 17:
13.01 – 13.02 Mb
PubMed search

Superoxide dismutase 2, mitochondrial (SOD2), also known as manganese-dependent superoxide dismutase (MnSOD), is an enzyme which in humans is encoded by the SOD2 gene on chromosome 6.[1][2]

Structure

The SOD2 gene contains five exons interrupted by four introns, an uncharacteristic 5′-proximal promoter that possesses a GC-rich region in place of the TATA or CAAT, and an enhancer in the second intron. The proximal promoter region contains multiple binding sites for transcription factors, including specific-1 (Sp1), activator protein 2 (AP-2), and early growth response 1 (Egr-1).[2] This gene is a the mitochondrial member of the iron/manganese superoxide dismutase family.[1][3] It encodes a mitochondrial matrix protein that forms a homotetramer and binds one manganese ion per subunit.[1][2] The manganese site forms a trigonal bipyramidal geometry with four ligands from the protein and a fifth solvent ligand. This solvent ligand is a hydroxide believed to serve as the electron acceptor of the enzyme. The active site cavity consists of a network of side chains of several residues associated by hydrogen bonding, extending from the aqueous ligand of the metal. Of note, the highly conserved residue Tyr34 plays a key role in the hydrogen-bonding network, as nitration of this residue inhibits the protein's catalytic ability.[4] This protein also possesses an N-terminal mitochondrial leader sequence which targets it to the mitochondrial matrix, where it converts mitochondrial-generated reactive oxygen species from the respiratory chain to H2.[2] Alternate transcriptional splice variants, encoding different isoforms, have been characterized.[1]

Function

As a member of the iron/manganese superoxide dismutase family, this protein transforms toxic superoxide, a byproduct of the mitochondrial electron transport chain, into hydrogen peroxide and diatomic oxygen.[1] This function allows SOD2 to clear mitochondrial reactive oxygen species (ROS) and, as a result, confer protection against cell death.[3] As a result, this protein plays an antiapoptotic role against oxidative stress, ionizing radiation, and inflammatory cytokines.[2]

Clinical significance

The SOD2 enzyme is an important constituent in apoptotic signaling and oxidative stress, most notably as part of the mitochondrial death pathway and cardiac myocyte apoptosis signaling.[5] Programmed cell death is a distinct genetic and biochemical pathway essential to metazoans. An intact death pathway is required for successful embryonic development and the maintenance of normal tissue homeostasis. Apoptosis has proven to be tightly interwoven with other essential cell pathways. The identification of critical control points in the cell death pathway has yielded fundamental insights for basic biology, as well as provided rational targets for new therapeutics a normal embryologic processes, or during cell injury (such as ischemia-reperfusion injury during heart attacks and strokes) or during developments and processes in cancer, an apoptotic cell undergoes structural changes including cell shrinkage, plasma membrane blebbing, nuclear condensation, and fragmentation of the DNA and nucleus. This is followed by fragmentation into apoptotic bodies that are quickly removed by phagocytes, thereby preventing an inflammatory response.[6] It is a mode of cell death defined by characteristic morphological, biochemical and molecular changes. It was first described as a "shrinkage necrosis", and then this term was replaced by apoptosis to emphasize its role opposite mitosis in tissue kinetics. In later stages of apoptosis the entire cell becomes fragmented, forming a number of plasma membrane-bounded apoptotic bodies which contain nuclear and or cytoplasmic elements. The ultrastructural appearance of necrosis is quite different, the main features being mitochondrial swelling, plasma membrane breakdown and cellular disintegration. Apoptosis occurs in many physiological and pathological processes. It plays an important role during embryonal development as programmed cell death and accompanies a variety of normal involutional processes in which it serves as a mechanism to remove "unwanted" cells.

Role in oxidative stress

Most notably, SOD2 is pivotal in reactive oxygen species (ROS) release during oxidative stress by ischemia-reperfusion injury, specifically in the myocardium as part of a heart attack (also known as ischemic heart disease). Ischemic heart disease, which results from an occlusion of one of the major coronary arteries, is currently still the leading cause of morbidity and mortality in western society.[7][8] During ischemia reperfusion, ROS release substantially contribute to the cell damage and death via a direct effect on the cell as well as via apoptotic signals. SOD2 is known to have a capacity to limit the detrimental effects of ROS. As such, SOD2 is important for its cardioprotective effects.[9] In addition, SOD2 has been implicated in cardioprotection against ischemia-reperfusion injury, such as during ischemic preconditioning of the heart.[10] Although a large burst of ROS is known to lead to cell damage, a moderate release of ROS from the mitochondria, which occurs during nonlethal short episodes of ischemia, can play a significant triggering role in the signal transduction pathways of ischemic preconditioning leading to reduction of cell damage. It has even observed that during this release of ROS, SOD2 plays an important role hereby regulating apoptotic signaling and cell death.

Due to its cytoprotective effects, overexpression of SOD2 has been linked to increased invasiveness of tumor metastasis.[3] Its role in controlling ROS levels also involves it in ageing, cancer, and neurodegenerative disease.[4] Mutations in this gene have been associated with idiopathic cardiomyopathy (IDC), sporadic motor neuron disease, and cancer. A common polymorphism associated with greater susceptibility to various pathologies is found in the mitochondrial leader targeting sequence (Val9Ala).[11] Mice lacking Sod2 die shortly after birth, indicating that unchecked levels of superoxide are incompatible with mammalian life.[12] However, mice 50% deficient in Sod2 have a normal lifespan and minimal phenotypic defects but do suffer increased DNA damage and increased incidence of cancer.[13] In Drosophila melanogaster, over-expression of Sod2 has been show to increase lifespan by 20%[14]

Exercise-induced cardioprotection

When animals are exercised at a relatively high work rate, many exercise training studies report that exercise training promotes an increase in myocardial MnSOD activity. This is significant because two recent studies reveal that increased MnSOD activity is essential to achieve optimal training-induced protection against both ischemia/reperfusion(IR)-induced cardiac arrhythmias and infarction. Specifically, using an antisense oligonucleotide against MnSOD to prevent ExTr-induced increases in myocardial MnSOD activity, Yamashita et al. demonstrated that an increase in myocardial MnSOD activity is required to provide training-induced protection against IR-induced myocardial infarction. Similarly, Hamilton et al. [10], using a MnSOD gene silencing approach, reported that prevention of the ExTr-induced increase in myocardial MnSOD resulted in a loss of training-induced protection against IR-mediated arrhythmias. In contrast to these findings, training-induced increases in cardiac MnSOD are not required to achieve training-induced cardioprotection against myocardial stunning. (Power et al. 2007)

Interactions

The SOD2 gene has been shown to bind:

The SOD2 protein has been shown to interact with HIV-1 Tat and HIV-1 Vif.[15]

References

  1. 1 2 3 4 5 "Entrez Gene: SOD2 superoxide dismutase 2, mitochondrial".
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Becuwe P, Ennen M, Klotz R, Barbieux C, Grandemange S (Dec 2014). "Manganese superoxide dismutase in breast cancer: from molecular mechanisms of gene regulation to biological and clinical significance". Free Radical Biology & Medicine 77: 139/51. doi:10.1016/j.freeradbiomed.2014.08.026. PMID 25224035.
  3. 1 2 3 Pias EK, Ekshyyan OY, Rhoads CA, Fuseler J, Harrison L, Aw TY (Apr 2003). "Differential effects of superoxide dismutase isoform expression on hydroperoxide-induced apoptosis in PC-12 cells". The Journal of Biological Chemistry 278 (15): 13294–301. doi:10.1074/jbc.M208670200. PMID 12551919.
  4. 1 2 Perry JJ, Hearn AS, Cabelli DE, Nick HS, Tainer JA, Silverman DN (Apr 2009). "Contribution of human manganese superoxide dismutase tyrosine 34 to structure and catalysis". Biochemistry 48 (15): 3417–24. doi:10.1021/bi8023288. PMID 19265433.
  5. ↑ Danial, NN; Korsmeyer, SJ (23 January 2004). "Cell death: critical control points.". Cell 116 (2): 205–19. doi:10.1016/s0092-8674(04)00046-7. PMID 14744432.
  6. ↑ Kerr JF, Wyllie AH, Currie AR (Aug 1972). "Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics". British Journal of Cancer 26 (4): 239–57. doi:10.1038/bjc.1972.33. PMC 2008650. PMID 4561027.
  7. ↑ Murray CJ, Lopez AD (May 1997). "Alternative projections of mortality and disability by cause 1990-2020: Global Burden of Disease Study". Lancet 349 (9064): 1498–504. doi:10.1016/S0140-6736(96)07492-2. PMID 9167458.
  8. ↑ Braunwald E, Kloner RA (Nov 1985). "Myocardial reperfusion: a double-edged sword?". The Journal of Clinical Investigation 76 (5): 1713–9. doi:10.1172/JCI112160. PMID 4056048.
  9. ↑ Maslov LN, Naryzhnaia NV, Podoksenov IuK, Prokudina ES, Gorbunov AS, Zhang I, Peĭ ZhM (Jan 2015). "[Reactive oxygen species are triggers and mediators of an increase in cardiac tolerance to impact of ischemia-reperfusion]". Rossiĭskii Fiziologicheskiĭ Zhurnal Imeni I.M. Sechenova / Rossiĭskaia Akademiia Nauk 101 (1): 3–24. PMID 25868322.
  10. ↑ Liem DA, Honda HM, Zhang J, Woo D, Ping P (Dec 2007). "Past and present course of cardioprotection against ischemia-reperfusion injury". Journal of Applied Physiology 103 (6): 2129–36. doi:10.1152/japplphysiol.00383.2007. PMID 17673563.
  11. ↑ Muller FL, Lustgarten MS, Jang Y, Richardson A, Van Remmen H (Aug 2007). "Trends in oxidative aging theories". Free Radical Biology & Medicine 43 (4): 477–503. doi:10.1016/j.freeradbiomed.2007.03.034. PMID 17640558.
  12. ↑ Li Y, Huang TT, Carlson EJ, Melov S, Ursell PC, Olson JL, Noble LJ, Yoshimura MP, Berger C, Chan PH, Wallace DC, Epstein CJ (Dec 1995). "Dilated cardiomyopathy and neonatal lethality in mutant mice lacking manganese superoxide dismutase". Nature Genetics 11 (4): 376–81. doi:10.1038/ng1295-376. PMID 7493016.
  13. ↑ Van Remmen H, Ikeno Y, Hamilton M, Pahlavani M, Wolf N, Thorpe SR, Alderson NL, Baynes JW, Epstein CJ, Huang TT, Nelson J, Strong R, Richardson A (Dec 2003). "Life-long reduction in MnSOD activity results in increased DNA damage and higher incidence of cancer but does not accelerate aging". Physiological Genomics 16 (1): 29–37. doi:10.1152/physiolgenomics.00122.2003. PMID 14679299.
  14. ↑ Curtis C, Landis GN, Folk D, Wehr NB, Hoe N, Waskar M, Abdueva D, Skvortsov D, Ford D, Luu A, Badrinath A, Levine RL, Bradley TJ, Tavaré S, Tower J (2007). "Transcriptional profiling of MnSOD-mediated lifespan extension in Drosophila reveals a species-general network of aging and metabolic genes". Genome Biology 8 (12): R262. doi:10.1186/gb-2007-8-12-r262. PMC 2246264. PMID 18067683.
  15. ↑ Woollard SM, Bhargavan B, Yu F, Kanmogne GD (Jun 2014). "Differential effects of Tat proteins derived from HIV-1 subtypes B and recombinant CRF02_AG on human brain microvascular endothelial cells: implications for blood-brain barrier dysfunction". Journal of Cerebral Blood Flow and Metabolism 34 (6): 1047–59. doi:10.1038/jcbfm.2014.54. PMC 4050250. PMID 24667918.

Further reading

  • Zelko IN, Mariani TJ, Folz RJ (Aug 2002). "Superoxide dismutase multigene family: a comparison of the CuZn-SOD (SOD1), Mn-SOD (SOD2), and EC-SOD (SOD3) gene structures, evolution, and expression". Free Radical Biology & Medicine 33 (3): 337–49. doi:10.1016/S0891-5849(02)00905-X. PMID 12126755. 
  • Faraci FM, Didion SP (Aug 2004). "Vascular protection: superoxide dismutase isoforms in the vessel wall". Arteriosclerosis, Thrombosis, and Vascular Biology 24 (8): 1367–73. doi:10.1161/01.ATV.0000133604.20182.cf. PMID 15166009. 
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