María’s comment on: Artificially Engineered Protein Hydrogels Adapted from the Nucleoporin Nsp1 for Selective Biomolecular Transport

Maria Luisa Adrover

 

MLAC blog image 18-05

The main goal of the article by the Olsen group is to present a new protein hydrogel composed of nucleoporin like polypeptides that allow a selective transport of biomolecules into the formed hydrogel. The engineering of this system was inspired by the selectivity of the protein matrix in the nuclear pore complex. The nuclear pore complex is composed of nucleoporins like Nsp1 (16 repeats of a 19 amino acid sequence). These are proteins containing Phe-Gly (FG) repeats that contribute to specific binding of the nuclear transport receptors. The authors took advantage of the finding that individual nucleoporins can form hydrogels in vitro. They designed three different nucleoporin-like polypeptides (NLP) using pentameric (P) coiled-coil domains in the C and N terminus of the polypeptide: P-1NLP-P, P-2NLP-P and P-cNsp1-P (the original nucleoporin).

In their experiments, they conducted rheology studies (using oscillations as a type stress) to evaluate the flow properties of the protein hydrogel. They found that the hydrogel in behaves in some cases as a viscous liquid (when G“ > G`) while in other cases it behaves as an elastic solid (when G` > G“). Also, they noticed by adding hexanediol, the FG repeats were weakened making the hydrogel less elastic. Another study was done using Raman spectroscopy too see any changes in the peaks of the spectra. They saw that by adding hexanediol there was a reduction the Phe vibrational mode of 486 cm-1 meaning that the FG repeats where indeed being disrupted. Lastly, using capillary experiments they studied the selective transport of the protein hydrogels. They studied the selectivity of the biomolecules measuring the fluorescence intensity of: Importin β, IBB-MBP-EGFP (Importin β binding with maltose binding protein and enhanced green fluorescent protein) and MBP-mCherry. Fluorescence studies showed that Importin β was diffused inside P-cNsp1-P hydrogel with the highest intensity, followed by P-2NLP-P and lastly P-1NLP-P. Interestingly, they showed that just by changing one amino acid (Serine to Aspartic Acid) the selectivity for Importin β changed. This suggested that small changes to the nucleoporin like polypeptides affects the selectivity. Adding 10% hexanediol to P-2NLP-P barely showed fluorescence mainly due to the FG disruptions mentioned before. Finally, a successful engineering of hydrogels was achieved showing a high selectivity just like the natural nucleoporin system. A relatively simple polypeptide chain just like the cNsp1 allow the design of nucleoporin-like polypeptides as selective as the protein matrix found inside the nuclear pore complex.


5 thoughts on “María’s comment on: Artificially Engineered Protein Hydrogels Adapted from the Nucleoporin Nsp1 for Selective Biomolecular Transport

  1. Rating (synopsis): 4/5
    Rating (figure): 4/5

    I found Maria’s paper one of the most difficult of the semester, mostly because the results are based on a somewhat different set of experiments that what we usually see. And maybe also because it didn’t go into many explanations on the molecular origin of the selectivity they observe, which is something we usually as a group look forward to when looking at literature. The synopsis is a brave attempt to explain the entirety of the paper and I think Maria does a good job at it. I might have suggested including a little less experimental details, even if not all of the work done is mentioned, to gain a bit in clarity, but that’s also a matter of style. Language is well used. I’d suggest that, in the ending of the synopsis, instead of “Finally”, the sentence should begin with “In summary” to better grasp the purpose of the following sentence.
    About the image, I’d represent the selective transport with another image, maybe a cartoon following what was used to illustrate the hydrogel… It’s hard to know what that graph means if you haven’t read the figure captions in the paper.

  2. Rating (synopsis): 4/5
    Rating (figure): 4/5

    This article contains experiments, such as rheology studies, that we are not familiar with, and Maria does a great job with the summary of these “new” experiments. I would add to the comment that the addition of the P copied-coil domains helps to improve the yield of the synthetic and original polypeptides, and I believe this to be critical for the future of this system.

    The image captures, in its simplicity, the essence of the article but I suggest to change one of the graphs with Figure 4a, which explains the experiment represented here and the selectivity of the hydrogel.

  3. Rating (synopsis): (4/5)
    Rating (figure): (4/5)

    The article by Olsen and his group shows a distinct approach from what the others articles were about which were about the LCST concept. This time they are modifyng polymers which is interesting since it can be attached to different applications. I could understand Maria’s synopsis and the purpose; although I’m not sure if I understood the procedure that they did to reach the final results.

    On the other hand, the image provides a better way to visualize the final results. Which are quite clear in the image that Maria did.

  4. Rating Synopsis 5/5
    Rating Figure 4/5

    This article was difficult to understand because they use concepts that I am not familiar with, however I think that Maria’s summery is really good, and helped me to understand a little bit more about what they did in the experiments. As Maria said, it was interesting how with minimum modifications like changing one amino acid in the chain affects the selectivity.
    As for the figure I think that provides information about the idea and results of the article, however it does not explain as good as the summery. Maybe it is helpful use another graph or add some imager cartoon that explains the graphs. Nevertheless, for me, Maria did a great job with this article.

  5. Rating (synopsis): 4/5
    Rating (figure): 4/5

    Maria’s take to summarize this article is a very impressive one. She summarized the rational with data in a very seemingly way that I hope we could all learn from. I would not have added that much data due to flow issues. By adding data, you are forced to explain experiments (as rheology). But for this paper is a price I’m willing to pay because it gave us the opportunity to learn new fields. Other than the overuse of data I see no major issue with this post. As the image goes, it goes perfectly with her narrative although not self-explanatory, so it’s a gray area I am not sure how to judge.

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