Free fatty acids are essential structural components of the cell, and their intracellular distribution and effects on membrane organelles have crucial roles in regulating the metabolism, development, and cell cycle of most cell types. Here we engineered novel fluorescent, polarity-sensitive fatty acid derivatives, with the fatty acid aliphatic chain of increasing length (from 12 to 18 carbons). As in the laurdan probe, the lipophilic acyl tail is connected to the environmentally sensitive dimethylaminonaphthalene moiety. The fluorescence lifetime imaging analysis allowed us to monitor the intracellular distribution of the free fatty acids within the cell, and to simultaneously examine how the fluidity and the microviscosity of the membrane environment influence their localization. Each of these probes can thus be used to investigate the membrane fluidity regulation of the correspondent fatty acid intracellular distribution. We observed that, in PC-12 cells, fluorescent sensitive fatty acid derivatives with increased chain length compartmentalize more preferentially in the fluid regions, characterized by a low microviscosity. Moreover, fatty acid derivatives with the longest chain compartmentalize in lipid droplets and lysosomes with characteristic lifetimes, thus making these probes a promising tool for monitoring lipophagy and related events.
Bibliographical noteFunding Information:
Funding: This research was funded by Università Cattolica del Sacro Cuore—Linea D1 2019, grant number R4124500312 and by an EFSD award, supported by EFSD and Sanofi European Research Grants for “Innovative Measurements of Diabetes Outcomes”. This study was also supported by a Bar-Ilan University new faculty grant to Arie Gruzman. Salome Azoulay-Ginsburg wishes to thank NAAMAT for the Edelson Foundation prize for outstanding women researchers in the field of chemistry and pharmacology and for the Navon fellowship for PhD students, awarded by the Israel Ministry of Science, Technology and Space. Israel Ministry of Immigration and Integration through Kamea fellowship supported Edward E. Korshin. (Grant number 8279).
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- Fatty acids analogs
- Laurdan derivatives
- Membrane fluidity
- Phasor analysis
- Two-photons mi-croscopy