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Published on: May 19, 2023
A Systematic Design and Synthesis of PET-based Fluorescent Probes for Monitoring pH During Mitophagy
Rashmi Yadav1, Subrata Munan1, Mudassar Ali2
1Molecular Sensors and Therapeutics (MST) Research Laboratory, Department of Chemistry, School of Natural Sciences, Shiv Nadar Institution of Eminence (SNIoE), Delhi NCR, NH 91, Tehsil Dadri, Greater Noida, Uttar Pradesh, 201314, India.
Abstract:
Mitochondria are the powerhouse of the cell and function at pH ∼8.0. Dysfunctions of mitochondria, includes mitochondrial damage, leading to pH alteration. Hence, researchers aim to develop efficient pH probes for tracking mitochondrial pH dynamics. Herein, we developed a PET-based fluorescent probe for pH monitoring during mitochondrial dysfunctions. Three derivatives were synthesized with a variable spacer's length in pentacyclic pyridinium fluorophores (PM-C2, PM-C3, and PM-C6). An efficient electron transfers from the receptor (tertiary amine) was observed in the case of PM-C2 compared to the other two derivatives. This PET process was inhibited when tertiary amine was protonated in acidic pH. However, PM-C3 showed minimal fluorescence intensity at similar conditions and almost negligible change in case of PM-C6, suggesting poor PET process for both the derivatives. Furthermore, DFT/TD-DFT quantum chemical calculation well supported this optical phenomena and PET process. Biocompatible, photostable, and mitochondria-specific PM-C2 could monitor pH dynamics during mitochondrial damage which were engulfed by lysosome, also known as mitophagy. This mitophagy process were induced by rapamycin and starvation, which can be monitored by turn-on fluorescence enhancement. This process was further validated by tracking Parkin-protein translocation from cytoplasm to damaged mitochondria using our developed probe.
Insights
Researchers developed a novel fluorescent probe to track mitochondrial pH changes during cell damage. This probe, PM-C2, offers a turn-on fluorescence response, aiding in the study of mitophagy.
Area of Science:
- Cell Biology
- Biochemistry
- Biophysics
Background:
- Mitochondria are vital organelles functioning optimally at pH ~8.0.
- Mitochondrial dysfunction, often involving damage, leads to significant pH alterations.
- Accurate monitoring of mitochondrial pH dynamics is crucial for understanding cellular health and disease.
Purpose of the Study:
- To develop a novel PET-based fluorescent probe for monitoring mitochondrial pH dynamics.
- To synthesize and characterize three pentacyclic pyridinium fluorophore derivatives (PM-C2, PM-C3, PM-C6) with varying spacer lengths.
- To investigate the probe's performance in tracking pH changes associated with mitochondrial damage and mitophagy.
Main Methods:
- Synthesis of three pentacyclic pyridinium fluorophore derivatives (PM-C2, PM-C3, PM-C6).
- Evaluation of the Photoinduced Electron Transfer (PET) process and its pH-dependent inhibition.
- Utilizing DFT/TD-DFT quantum chemical calculations to support observed optical phenomena.
- Assessing probe biocompatibility, photostability, and mitochondria-specificity.
- Monitoring mitophagy induced by rapamycin and starvation via fluorescence enhancement.
- Tracking Parkin-protein translocation to damaged mitochondria.
Main Results:
- PM-C2 exhibited efficient PET, which was inhibited under acidic conditions due to tertiary amine protonation.
- PM-C3 and PM-C6 showed poor PET processes with minimal fluorescence changes in acidic pH.
- PM-C2 demonstrated biocompatibility, photostability, and specific targeting of mitochondria.
- The probe successfully monitored pH dynamics during mitophagy, showing a turn-on fluorescence enhancement.
- Parkin-protein translocation during mitophagy was validated using the developed probe.
Conclusions:
- PM-C2 is a highly effective PET-based fluorescent probe for monitoring mitochondrial pH dynamics.
- The probe enables real-time tracking of mitophagy and associated mitochondrial damage.
- This tool facilitates further research into mitochondrial dysfunction and related cellular processes.
