Snapshots of Life: Biological Bubble Machine

plasma membrane vesicles

Credit: Chi Zhao, David Busch, Connor Vershel, Jeanne Stachowiak, University of Texas at Austin

As kids, most of us got a bang out of blowing soap bubbles and watching them float around. Biologists have learned that some of our cells do that too. On the right, you can see two cells (greenish yellow) in the process of forming bubbles, or plasma membrane vesicles (PMVs). During this blebbing process, a cell’s membrane temporarily disassociates from its underlying cytoskeleton, forming a tiny pouch that, over the course of about 30 minutes, is “inflated” with a mix of proteins and lipids from inside the cell. After the PMVs are fully filled, these bubble-like structures are pinched off and released, like those that you see in the background. Certain cells constantly release PMVs, along with other types of vesicles, and may use those to communicate with other cells throughout the body.

This particular image, an entrant in the Biophysical Society’s 2017 Art of Science Image Contest, was produced by researchers working in the NIH-supported lab of Jeanne Stachowiak at the University of Texas at Austin. Stachowiak’s group is among the first to explore the potential of PMVs as specialized drug-delivery systems to target cancer and other disorders [1].

Until recently, most efforts to exploit vesicles for therapeutic uses have employed synthetic versions of a different type of vesicle, called an exosome. But Stachowiak and others have realized that PMVs come with certain built-in advantages. A major one is that a patient’s own cells could in theory serve as the production facility.

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Cool Videos: Pushing the Limits of Live-Cell Microscopy

Actin

If you’re not watching recent work in biology, you might have thought that light microscopy hit its limits years ago.  After all, it’s been around a long time. But to the contrary, microscopic imaging technology just keeps getting better and better. Here you can look with unprecedented clarity at just one of the many dynamic processes going on within a living cell. Specifically, this video shows actin fibers (orange-red), which are key components of the cell’s cytoskeleton, slowly pulling clathrin-coated pits (green), which are basket-like structures containing molecular cargo, away from the cell’s external membrane and deeper within the cell.

This remarkable live-action view was produced using one of two new forms of extended-resolution, structured illumination microscopy (SIM). SIM is faster than other forms of super-resolution fluorescence microscopy. It’s also less damaging to cells, making it the go-to method for live-cell imaging. The downside has been SIM’s limited resolution—just twice that of conventional light microscopes. However, Nobel Prize-winner Eric Betzig and postdoc Dong Li of Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA, along with colleagues including Jordan Beach and John Hammer at NIH’s National Heart, Lung, and Blood Institute, recently came up with two different solutions to enhance SIM’s spatial resolution.

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Snapshots of Life: Cell Skeleton on the Move

Keratinocyte

Credit: Torsten Wittmann, University of California, San Francisco

Cells are constantly on the move. They shift, grow, and migrate to new locations—for example, to heal a wound or to intercept an infectious agent as part of an immune response. But how do cells actually move?

In this image, Torsten Wittmann, an NIH-funded cell biologist at the University of California, San Francisco, reveals the usually-invisible cytoskeleton of a normal human skin cell that lends the cell its mobility. The cytoskeleton is made from protein structures called microtubules—the wispy threads surrounding the purple DNA-containing nucleus—and filaments of a protein called actin, seen here as the fine blue meshwork in the cell periphery. Both actin and microtubules are critical for growth and movement.

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The Beauty of Smooth Muscle

We humans have long wondered how, exactly, we develop from embryos into adults. This photo of an embryonic smooth muscle cell hints at the tremendous complexity of this fundamental biological mystery. And for those of you who might be wondering just what smooth muscles are, they’re the involuntary muscles found in places like the walls of our blood vessels, the digestive tract, the bladder, and the respiratory system.

This exquisite photo was produced using laser scanning confocal microscopy — a precise imaging method that includes the dimension of depth for scientific analysis. Here, green is used to label thin filaments of the protein actin, which is a key component of the cell’s cytoskeleton, and blue indicates another protein, called vinculin, which is enriched in locations involved in cell-cell adhesion.

Slowly but surely, using all the technology and tools available to us, we are unraveling the mysteries of biology — and turning our discoveries into health.