In the sting of the jellyfish: investigating the microarchitecture of a cellular weapon

Fluorescent microscopy (top) and model (bottom) show the mechanism for the sea anemone stinging organelle in three distinct phases. Credit: Gibson Lab, Stowers Institute of Medical Research.

Summer beachgoers are all too familiar with the painful reality of a jellyfish sting. But how do the stinging cells of jellyfish and their coral and sea anemone cousins ​​actually work? New research from the Stowers Institute for Medical Research reveals an accurate operational model for the stinging organelle of the starlet sea anemone, Nematostella vectensis. The study, published online in nature communication on June 17, 2022, was led by Ahmet Karabulut, a predoctoral researcher in the lab of Matt Gibson, Ph.D. Their work involved the application of advanced microscopic imaging technologies and the development of a biophysical model to enable a comprehensive understanding of a mechanism that has remained elusive for more than a century. Insights from the work could lead to useful applications in medicine, including the development of microscopic therapeutic delivery devices for humans.

The Stowers team’s new model for stinging cell function provides crucial insights into the extraordinarily complex architecture and firing mechanism of nematocysts, the technical name for hives stinging organelles. Karabulut and Gibson, in collaboration with scientists at the Stowers Institute Technology Centers, used advanced imagingthree-dimensional electron microscopy and gene knockdown approaches to discover that the kinetic energy required to pierce and poison a target involving both osmotic pressure and elastic energy stored in multiple nematocyst substructures.

Serial electron microscopy images were used to create a 3D reconstruction of the sea anemone’s stinging organelle. Credit: Gibson Lab, Stowers Institute of Medical Research.

“We used” fluorescence microscopyadvanced imaging techniques and 3D electron microscopy combined with genetic perturbations to understand the structure and mechanism of action of nematocysts,” Karabulut said.

Using these state-of-the-art methods, the researchers characterized the explosive discharge and biomechanical transformation of N. vectensis nematocysts during firing, grouping this process into three different phases† The first stage is the initial, projectile-like discharge and target penetration of a tightly coiled filament from the nematocyst capsule. This process is driven by a change in osmotic pressure due to the sudden influx of water and elastic stretching of the capsule. The second stage marks the discharge and elongation of the thread’s shaft substructure, which is further propelled by the release of elastic energy through a process called eversion – the mechanism where the shaft turns inside out – forming a triple helical structure to form a to surround a fragile inner tube decorated with barbs that contain a cocktail of toxins. In the third stage, the tubule then begins its own eversion process to elongate into the target’s soft tissue, releasing neurotoxins along the way.

“Understanding this complex stinging mechanism could have potential future applications for humans,” Gibson said. “This could lead to the development of new therapeutic or targeted drug delivery methods, as well as the design of microscopic devices.”

During feeding, the tentacles of the sea anemone catch the brine shrimp. Credit: Gibson Lab, Stowers Institute of Medical Research.

The entire stinging operation is completed in just a few thousandths of a second, making it one of nature’s fastest biological processes. “The earliest stage of the firing of the nematocyst is extremely rapid and difficult to capture in detail,” Karabulut said.

As is often the case with basic biological research, the initial discovery was a fluke. Karabulut incorporated fluorescent dye into a sea anemone to see what it looked like when the nematocy-streaked tentacles were activated. After applying a combination of solutions to both trigger the discharge of nematocysts while preserving their delicate substructures in time and space, he was shocked to accidentally trap multiple nematocysts at different stages of firing.

“Under the microscope, I saw a stunning snapshot of the threads being discharged on a tentacle. It was like a fireworks display. I realized that nematocysts were partially discharging their threads while the reagent I was using simultaneously and instantly fixed the samples,” Karabulut said.

In the sting of the jellyfish: investigating the microarchitecture of a cellular weapon

Sea anemone stings in multiple stages of firing. Credit: Gibson Lab, Stowers Institute of Medical Research.

“I was able to capture images showing the geometric transformations of the wire during firing in a beautifully orchestrated process,” Karabulut said. “After further investigation, we were able to fully understand the geometric transformations of the nematocyst thread during its operation.”

Elucidating the elaborate choreography of firing nematocysts in a sea anemone has some interesting implications for the design of engineered microscopic devices, and this joint effort between the Gibson Lab and the Stowers Institute Technology Centers may have future applications for drug delivery to humans at the cellular level.

Co-authors include Melainia McClain, Boris Rubinstein, Ph.D., Keith Z. Sabin, Ph.D., and Sean McKinney, Ph.D.

Jellyfish venom capsule length association with pain

More information:
Ahmet Karabulut et al, The architecture and mechanism of action of a hives stinging organelle, nature communication (2022). DOI: 10.1038/s41467-022-31090-0

Quote: In the sting of the jellyfish: Investigating the microarchitecture of a cellular weapon (2022, June 23) retrieved June 23, 2022 from cellular-weapon.html

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