Look beyond plasma membrane biophysics: mapping the dipole potential of organelles of living cells | Department of Biophysics and Cell Biology

Based on our current knowledge the biophysical properties of cellular membranes are determined by their composition and can be described by three quantitative parameters: fluidity, hydration and dipole potential – the latter of the three being one of the main interests of the Quantitative Receptor Analysis workgroup of the Department of Biophysics and Cell Biology. The above three parameters give information about the structural organization of membrane layers at different depths. In the absence of appropriate measurement methods such information was mainly available of the plasma membrane in living cells, leaving the organization of intracellular membrane systems a mystery – this is challenged by Dr. Tamas Kovacs and colleagues in their latest publication in the International Journal of Molecular Sciences.
In many pathological processes – for example metabolic and lysosomal storage diseases, certain tumours – changes in the lipid composition of cellular membrane can be observed. In order to identify potential therapeutic targets a deep understanding of the pathomechanism, even on a molecular level, is crucial. Using the novel measurement method, published in the International Journal of Molecular Sciences, a major biophysical parameter, the dipole potential, and its alterations can be quantified in the above disorders.
The authors examined the magnitude of dipole potential of the plasma membrane and that of different subcellular compartments in a comparative analysis with a novel quantitative confocal microscopy-based method applying the voltage-sensitive F66 fluorophore and fluorescent organelle markers. According to their results, the dipole potential exhibits an inward decreasing tendency on the route of organelles of the secretory/endocytic pathway (plasma membrane >> lysosome > Golgi apparatus > endoplasmic reticulum) and the dipole potential of mitochondrial membranes is similar to that of lysosomes. Identical results have been obtained in three different human cell lines suggesting a universal rule amongst human cells.
The results shown in the publication offer insights into the structural organization of intracellular membranes of individual, intact living cells applying a simple, easy-to-use method that can be utilized to identify the affected organelles and potential therapeutic targets in diseases associated with alterations in membrane lipid composition and thus biophysics such as tumours, metabolic, neurodegenerative, or lysosomal storage disorders.
The publication „Look Beyond Plasma Membrane Biophysics: Revealing Considerable Variability of the Dipole Potential Between Plasma and Organelle Membranes of Living Cells” by Mate Szabo, Bence Cs.Szabo, Kitti Kurtan, Zoltan Varga, Gyorgy Panyi, Peter Nagy, Florina Zakany and Tamas Kovacs can be read in full length in the International Journal of Molecular Sciences (DOI: 10.3390/ijms26030889).