Plant Cell Wall-Penetrable, Redox-Responsive Silica Nanoprobe for the Imaging of Starvation-Induced Vesicle Trafficking.
Autophagy is a self-protection process against reactive oxygen species (ROS). The intracellular level of ROS increased when cells were cultured under nutrient starvation. Antioxidants such as glutathione and ascorbic acid play an important role in ROS removal. However, the cellular redox state in the autophagic pathway is still unclear. Herein, we developed a new redox-sensitive probe with a disulfide-linked silica scaffold to enable the sensing of the reduction environment in cell organelles. This redox-responsive silica nanoprobe (ReSiN) could penetrate the plant cell wall and release fluorescent molecules in response to redox states. By applying the ReSiN to tobacco BY-2 cells and tracing the distribution of fluorescence, we found a higher reducing potential in the central vacuole than in the autolysosomes. Upon cysteine protease inhibitor (E64-c) treatment in sucrose-free medium, the disulfide-silica structures of the ReSiNs were broken down in the vacuoles but were not degraded and were accumulated in the autolysosomes. These results reveal the feasibility of our nanoprobe for monitoring the endocytic and macroautophagic pathways. These pathways merge upstream of the central vacuole, which is the final destination of both pathways. In addition, different redox potentials were observed in the autophagic pathway. Finally, the expression of the autophagy-related protein (Atg8) fused with green fluorescence protein confirmed that the ReSiN treatment itself did not induce the autophagic pathway under normal physiological conditions, indicating the versatility of this nanoprobe in studying stimuli-triggered autophagy-related trafficking.
Department of Applied Chemistry and Institute of Molecular Science, National Chiao-Tung University , No. 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Xin-Chun
XC
Huang
Graduate School of Science and Engineering, Saitama University , Shimo-Ohkubo 255, Sakura-Ku, Saitama 338-8570, Japan.
Yuko
Y
Inoue-Aono
Graduate School of Science and Engineering, Saitama University , Shimo-Ohkubo 255, Sakura-Ku, Saitama 338-8570, Japan.
Yuji
Y
Moriyasu
Department of Applied Chemistry and Institute of Molecular Science, National Chiao-Tung University , No. 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Pei-Ying
PY
Hsieh
Department of Applied Chemistry and Institute of Molecular Science, National Chiao-Tung University , No. 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Wei-Ming
WM
Tu
Department of Applied Chemistry and Institute of Molecular Science, National Chiao-Tung University , No. 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Shae-Chien
SC
Hsiao
Institute of Plant and Microbial Biology, Academia Sinica , Taipei 11529, Taiwan.
Wan-Neng
WN
Jane
Department of Applied Chemistry and Institute of Molecular Science, National Chiao-Tung University , No. 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
Hsin-Yun
HY
Hsu