GLB-13 is associated with oxidative stress resistance in Caenorhabditis elegans

Changhong Ren^1,4 *, Yuan Li^1,2*, Rongrong Han^1,2*, Dawen Gao¹*, Weiguang Li¹, Jinping Shi¹, David Hoogewijs³, Bart P Braeckman³, Sasha De Henau³, Yiming Lu¹, Wubin Qu¹, Yan Gao¹, Yonghong Wu¹, Zhihui Li¹, Huqi Liu², Zhaoyan Wang⁵, Chenggang Zhang^1§

^§Corresponding author: Chenggang Zhang, Beijing Institute of Radiation Medicine, Taiping Road 27, Beijing 100850, China. Tel/Fax: +86-10-68169574, E-mail: zhangcg@bmi.ac.cn

Running title: GLB-13 associate with oxidative stress resistance

Abstract

Globins constitute a superfamily of heme-binding proteins that is widely present in many species. There are 33 putative globins in the genome of C. elegans, where glb-13 is a homolog of neuroglobin (Ngb) based on sequence analysis and specific expression in neurons. Here we examined whether glb-13 as well as Ngb is also associated with resistance to reactive oxygen species (ROS) induced by paraquat. Our results showed that the mRNA level of glb-13 was significantly upregulated after paraquat exposure. Expression of a GFP reporter gene directed by the glb-13 promoter was increased by paraquat exposure. The mutant C. elegans strain glb-13(tm2825) was sensitive to paraquat-induced oxidative stress. Overexpression of human Ngb (hNgb) in C. elegans neuronal cells can rescue the paraquat sensitive phenotype of the mutant strain. glb-13 mutation or hNgb overexpression did not affect the expression of antioxidant enzymes such as superoxide dismutase (SOD). To examine the ROS-scavenging capabilities of hNgb and glb-13, we further examined the level of ROS in glb-13 mutant and hNgb transgenic (hNgb-Tg) worms. There was no statistical difference in ROS levels in the untreated controls, however in paraquat-treated worms, the ROS level was statistically repressed in the hNgb-Tg relative to enhanced green fluorescent protein (EGFP)-Tg worms or wildtype animals. Additionally, the ROS level of glb-13 mutant was statistically higher than the wildtype animals. Furthermore, hNgb overexpression diminished the ROS level of glb-13 mutant. In conclusion, hNgb can rescue the ROS sensitive phenotype of the glb-13 mutant strain. The protein GLB-13 seems to have an hNgb-like function, suggesting the importance of the globin protein family in maintaining the homeostasis of ROS signals. Our data provided evidence for the first time that glb-13 is associated with the resistance against oxidative stress-induced toxicity.

Keywords: glb-13; neuroglobin; paraquat; ROS; transgenic; Caenorhabditis elegans