Superior cell penetration by a rigid and anisotropic synthetic protein

Our plain-English summary of Superior cell penetration by a rigid and anisotropic synthetic protein, by N. Nakayama, K. Hagiwara, Y. Ito, et al (Langmuir, 2015).

The study

• Authors: N. Nakayama, K. Hagiwara, Y. Ito, K. Ijiro, Y. Osada, K. Sano
• Journal: Langmuir
• Published: 2015;31(9):2826-32
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Molecules with structural anisotropy and rigidity, such as asbestos, demonstrate high cell-penetrating activity but also high toxicity. Here we synthesize a biodegradable, rigid, and fibrous artificial protein, CCPC 140, as a potential vehicle for cellular delivery. CCPC 140 penetrated 100% of cells tested in vitro, even at a concentration of 3.1 nM-superior to previously reported cell-penetrating peptides. The effects of cell-strain-dependency and aspect ratio on the cell-penetrating activity of CCPC 140 were also investigated.

In plain English

This laboratory study did not test asbestos or study anyone exposed to asbestos. The authors mentioned asbestos only as background, citing earlier work linking its toxicity to its ready entry into cells. They built a synthetic, biodegradable protein called CCPC 140, based on the muscle protein tropomyosin, as a possible carrier for delivering drugs into cells. They tested it on human cell lines grown in dishes. At 100 nM, labeled CCPC 140 entered 100% of HeLa cells after 48 hours. An unmodified tropomyosin fragment of the same length showed no cell entry. At 3.125 nM, 100% of HeLa cells still appeared to take up CCPC 140. It also entered three other cell lines (A549, Hep3B and K562). No short-term cell toxicity was seen over 72 hours at 1 micromolar. Versions 12 to 20 nm long entered cells about equally well. Shorter versions, and the longest version (28 nm), entered less well, though the authors said the effect of length remained unclear. The authors concluded that structural rigidity was the most important factor in the protein's ability to enter cells. They said its stability inside a living body still needs to be studied.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) experiment on cultured cell lines using a designed synthetic protein. No asbestos was tested; asbestos appears only as background from earlier studies.
• Who was studied: Cultured human cell lines: HeLa cells, plus Hep3B human hepatocellular carcinoma cells, A549 human lung adenocarcinoma epithelial cells, and K562 human erythromyeloblastoid leukemia cells. No people or animals were studied.
• Exposure: Fluorescently labeled synthetic coiled-coil protein CCPC 140 and its shorter and longer variants, compared with tropomyosin controls. HeLa cells received concentrations from 100 nM down to 3.125 nM. No asbestos exposure was studied.
• Main results:
  • In HeLa cells given 100 nM labeled CCPC 140 for 48 hours, the protein entered 100% of cells.
  • The control protein, a fragment of human skeletal muscle tropomyosin (Hu-sk α-Tm 140), did not enter cells.
  • At 3.125 nM, 100% of HeLa cells appeared to take up CCPC 140.
  • CCPC 140 entered 100% of the cells of all lines tested, including K562 cells.
  • No short-term (72-hour) toxicity to cells was seen at 1 μM CCPC 140.
  • Variants 12 to 20 nm long showed nearly identical cell-penetrating activity.
  • Shortening the protein further reduced its uptake into cells.
  • The longest variant, CCPC 195 (28 nm), also showed lower activity than CCPC 140.
• The authors' conclusion: The authors concluded that structural rigidity was the most important factor in the proteins' cell-penetrating activity, and that these proteins have potential as carriers for delivering drugs into cells.
• Limitations the authors state:
  • The effect of protein length remained unclear because the short proteins were unstable with temperature.
  • Testing at even lower concentrations was limited by the detection limit of the fluorescence.
  • Actual delivery of therapeutic cargo, stability in living organisms, and targeting were not studied and are left for future work.

Topics

Medical terms in this study, explained in our Lexicon: Aspect Ratio (Length-to-diameter ratio).

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