Lipid droplets: biophysics of the first steps of biogenesis

MURATORI BREST, PAULA; CROSIO, MATIAS; WILKE, NATALIA; CARUSO, BENJAMIN

Rosario, Santa Fe

Congreso; L Reunión Anual SAB; 2022

Asociación Argentina de Biofísica (SAB)

"Lipid droplets” (LDs) are intracellular structures that bud from the endoplasmic reticulummembrane (ERM) and are formed by a neutral lipid (NL) nucleus surrounded by a singlelayer of phospholipids (PLs) and proteins. They are recognized as key organelles inintracellular physiology because of their multiple roles within cell biology; playing a rolein several diseases such as dengue, coronavirus and non-viral infections, cancer andobesity. The dynamics of LDs among them vary greatly, but these differences can beaccounted for by their assembly and disassembly processes. This study aimed tocontribute to this objective from a biophysical approach, focusing on the molecularmechanisms that govern the first stages of its biogenesis; particularly, those that triggerthe accumulation and budding of NL within the ERM. For this purpose, we used modelmonolayers (Langmuir films) and bilayers (Giant Unilamellar Vesicles) made of triolein (TO)as NL and PLs with different spontaneous curvatures (POPE (-), POPC (0) and LysoPC (+))to study their influence on the stability and topology of the TO structures formed. We alsotook advantage of the solvatochromic properties of the Nile Red (NR) fluorescent probe toevidence the presence of TO blisters inside the bilayer, while observing the effect of aninduced bilayer compression on their emission spectra. Results on monolayers show thatPL's curvature affects the height but not the diameter or density of the TO lenses formed.In turn, the vesicles were successfully shrinked (>10% diameter) by osmotic shock.However, the emission spectra of NR in the bilayers did not evidence the accumulation ofTO aggregates, even under bilayer compression. Furthermore, when GUVs where over-irradiated (lex 488 and 543 nm), the spectra of NR in the bilayers exhibited differentpopulations, even in the absence of TO. Therefore, the incorporation of non-aggregatedTO molecules into the bilayer is being studied by its bending rigidity properties.