Inactive extracellular superoxide dismutase disrupts secretion and function of active extracellular superoxide dismutase.
Extracellular superoxide dismutase (EC-SOD) is an antioxidant enzyme that protects cells and tissues from extracellular damage by eliminating superoxide anion radicals produced during metabolism. Two different forms of EC-SOD exist, and their different enzyme activities are a result of different disulfide bond patterns. Although only two folding variants have been discovered so far, five folding variants are theoretically possible. Therefore, we constructed five different mutant EC-SOD expression vectors by substituting cysteine residues with serine residues and evaluated their expression levels and enzyme activities. The mutant EC-SODs were expressed at lower levels than that of wild-type EC-SOD, and all of the mutants exhibited inhibited extracellular secretion, except for C195S ECSOD. Finally, we demonstrated that co-expression of wild-type EC-SOD and any one of the mutant EC-SODs resulted in reduced secretion of wild-type EC-SOD. We speculate that mutant EC-SOD causes malfunctions in systems such as antioxidant systems and sensitizes tissues to ROS-mediated diseases.
Laboratory of Dermato-Immunology, Catholic Research Institute of Medical Science, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Byeongwook
B
Jeon
Byung Hak
BH
Kim
Yun Sang
YS
Lee
Sungsub
S
Kim
Jong-Bok
JB
Yoon
Tae-Yoon
TY
Kim
D019943:Amino Acid Substitution; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D013481:Superoxides / Q000737:chemistry
D004220:Disulfides; D013481:Superoxides; C441642:SOD3 protein, human; D013482:Superoxide Dismutase; D003545:Cysteine