Giant organelle vesicles to uncover intracellular membrane mechanics and plasticity

Cell organelles are like tiny machines, each with its unique structure and function. Understanding how these organelles work and interact with each other is crucial for unraveling the mysteries of life. However, studying organelles has always been challenging due to their small size and complex environment within the cell. Now, a groundbreaking method offers a new way to access and study organelles like never before.

Researchers at the PSL Université Paris have developed a novel technique to generate giant organelle vesicles (GOVs) from cells. These GOVs, ranging from 3 to over 10 micrometers in size, provide researchers with a large and manipulable platform to study organelles up close. By subjecting cells to a hypotonic medium followed by plasma membrane breakage, researchers can isolate GOVs derived from various organelles such as the endoplasmic reticulum, endosomes, lysosomes, and mitochondria.

GERVs reproduce lipid droplet assembly

Fig. 4

a Confocal microscopy image of harvested Giant ER Vesicles (GERVs) containing seipin/KDEL. Scale bar: 5 µm. b Confocal microscopy image of an isolated Giant ER Vesicles (GERVs) containing seipin/sec61ß. Scale bar: 5 µm. c Top left: Representation of a membrane nanotube extracted from a seipin/sec61ß-based Giant ER Vesicle. The rectangular shape indicates the region of interest. Top right: Confocal microscopy snapshot of the nanotube extracted from the seipin/sec61ß-based Giant ER Vesicle. Middle: Fluorescence profiles drawn perpendicular to the membrane at both the flat region and the nanotube. Intensities are in arbitrary units. d Confocal microscopy image of a nanotube extracted from a seipin-based Giant ER Vesicle (GERV), which was fed with OCoA and DAG five minutes before tube pulling. LipidTox fluorescence is used to report for the hydrophobicity of the membrane. e The membrane tube shown in (d) is pulled to increase its curvature, resulting in the appearance of seipin puncta in the tube. Some seipin puncta are LipidTox-condensed (indicated by yellow arrows), while others lack LipidTox puncta (red arrows). All LipidTox puncta colocalize with seipin spots. Fluorescence profiles indicate the enrichment of LipidTox at specific spots in the tube. f Left: fraction of nucleation events observed following tube pulling and curvature increase. A nucleation event is considered when at least one LipidTox-positive puncta forms in the tubule. Right: Frequency of nascent LipidTox-positive nascent LD colocalization with a seipin cluster. g Confocal microscopy snapshots of a nanotube extracted from a Giant ER Vesicle (GERV) with seipin overexpressed, and supplied with the substrates for triacylglycerol synthesis. LipidTox fluorescence is monitored to visualize the formation of a nascent LD in the tube. Arrows indicate the appearance of an oil lens (t = 10 s) after the formation of a seipin spot (t = 5 s).

What makes GOVs particularly exciting is their ability to mimic the properties of organelles within the cell. By measuring the mechanical properties of these organelle-derived GOVs, the researchers have discovered that each type of GOV has distinct characteristics. For example, GOVs derived from the endoplasmic reticulum tend to have different bending rigidities compared to those derived from the plasma membrane.

Furthermore, the researchers have found that the mechanical properties of giant endoplasmic reticulum vesicles (GERVs) can vary depending on their interactions with other organelles or the metabolic state of the cell. This highlights the dynamic nature of organelles within the cell and their ability to adapt to different conditions.

But GOVs aren’t just passive structures; they also exhibit biochemical activity similar to their counterparts in living cells. The researchers have demonstrated that GERVs have the capacity to synthesize triglycerides and assemble lipid droplets, showcasing their functional capabilities.

These findings open up new possibilities for studying the biophysics and biology of organelles. By providing researchers with a versatile and accessible tool for studying organelles in isolation, GOVs have the potential to revolutionize our understanding of cellular processes. Whether it’s unraveling the mechanics of organelle membranes or investigating their biochemical functions, GOVs offer a window into the inner workings of cells like never before.

Santinho A, Carpentier M, Lopes Sampaio J, Omrane M, Thiam AR. (2024) Giant organelle vesicles to uncover intracellular membrane mechanics and plasticity. Nat Commun 15(1):3767. [article]

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