One enzyme, two functions: PON2 prevents mitochondrial superoxide formation and apoptosis independent from its lactonase activity.
The human enzyme paraoxonase-2 (PON2) has two functions, an enzymatic lactonase activity and the reduction of intracellular oxidative stress. As a lactonase, it dominantly hydrolyzes bacterial signaling molecule 3OC12 and may contribute to the defense against pathogenic Pseudomonas aeruginosa. By its anti-oxidative effect, PON2 reduces cellular oxidative damage and influences redox signaling, which promotes cell survival. This may be appreciated but also deleterious given that high PON2 levels reduce atherosclerosis but may stabilize tumor cells. Here we addressed the unknown mechanisms and linkage of PON2 enzymatic and anti-oxidative function. We demonstrate that PON2 indirectly but specifically reduced superoxide release from the inner mitochondrial membrane, irrespective whether resulting from complex I or complex III of the electron transport chain. PON2 left O(2)(-) dismutase activities and cytochrome c expression unaltered, and it did not oxidize O(2)(-) but rather prevented its formation, which implies that PON2 acts by modulating quinones. To analyze linkage to hydrolytic activity, we introduced several point mutations and show that residues His(114) and His(133) are essential for PON2 activity. Further, we mapped its glycosylation sites and provide evidence that glycosylation, but not a native polymorphism Ser/Cys(311), was critical to its activity. Importantly, none of these mutations altered the anti-oxidative/anti-apoptotic function of PON2, demonstrating unrelated activities of the same protein. Collectively, our study provides detailed mechanistic insight into the functions of PON2, which is important for its role in innate immunity, atherosclerosis, and cancer.
Department of Pharmacology, University Medical Center, Johannes Gutenberg University, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany.
Sebastian
S
Altenhöfer
Ines
I
Witte
John F
JF
Teiber
Petra
P
Wilgenbus
Andrea
A
Pautz
Huige
H
Li
Andreas
A
Daiber
Heidrun
H
Witan
Albrecht M
AM
Clement
Ulrich
U
Förstermann
Sven
S
Horke
D000975:Antioxidants / Q000737:chemistry; D017209:Apoptosis; D043303:Aryldialkylphosphatase / Q000737:chemistry / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology; D006031:Glycosylation; D006801:Humans; D007783:Lactones / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D017382:Reactive Oxygen Species; D013347:Subcellular Fractions; D013481:Superoxides / Q000378:metabolism*
D000975:Antioxidants; D007783:Lactones; D017382:Reactive Oxygen Species; D013481:Superoxides; D043303:Aryldialkylphosphatase; D010100:Oxygen