New nanosensor can live-track a proteins’ pathway through the cell.

Membrane proteins are a foundational component of every cell in the human body and play a vital role in the cell’s structure, metabolism and transport. They ensure that substances, such as proteins, are transported to and from the cell.  It is quite easy to determine the distribution of membrane proteins in the cell, however, tracking the paths they take within the cell and identifying their intended destination is considerably more difficult.  Now, a study from researchers at the University of Basel develops a method for tracing the movement of proteins within the cell. The team state they tagged proteins with tiny nanosensors, called nanobodies, which enabled them to live-track and trace the proteins’ pathway through the cell in real-time. The study is published in the journal PNAS.

Previous studies show that nanobodies have been used extensively in the fields of research, diagnostics and therapy. These antigen binding fragments, originating from camelid heavy-chain antibodies, possess unusual hallmarks in terms of size, stability, solubility and specificity, hence allowing cost-effective production and sometimes outperforming monoclonal antibodies.  This means that nanobodies can be applied as highly specific diagnostic agents and molecular imaging probes.  The current study establishes functionalized nanobodies as a powerful tool to demonstrate and quantify retrograde transport pathways in cells.

The current study develops nanobodies, tiny antibody fragments, consisting solely of a single protein chain and so, in contrast to antibodies which are composed of four proteins, they have the advantage to be only about one-tenth of the size, very compact and stable.  The nanobodies, originally obtained from camels and llamas, were altered to enable production with the help of bacteria and use as nanosensors which fluoresce.  Results show that the nanobodies successfully attach to the targeted protein, where they remain fastened no matter which path the protein takes to enter the cell. Data findings show that by using a microscope, the path of entry and distribution of surface proteins can be observed in living cells.

The group state that their nanosensor with its fluorescent dye makes the exact movements of the proteins visible. They go on to add that this enables the ability to follow the natural pathways taken by the proteins into the cell, as well as the speed of transport within the cell.  Furthermore, the lab altered the nanobodies so the proteins could be localized in the cell by an electron microscope.

The team surmise they have developed a new nanobody tool to observe the movement of proteins into and out of the cell.  For the future, the researchers plan to apply this new method to track and trace various proteins and to more closely study their transport pathways.

Source: University of Basel’s Biozentrum



Nanobodies track receptors from the cell surface to the center of the cell (the Golgi apparatus). Right: electron microscope image. (Image: University of Basel, Biozentrum)

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