Nuclear pore complexes are tiny channels where the exchange of substances between the cell nucleus and the cytoplasm takes place. Scientists at the University of Basel report on startling new research that might overturn established models of nuclear transport regulation. Their study published in the Journal of Cell Biology reveals how shuttling proteins known as importins control the function of nuclear pores – as opposed to the view that nuclear pores control the shuttling of importins.
Genetic information is protected in the cell nucleus by a membrane that contains numerous nuclear pores. These pores facilitate the traffic of proteins known as importins that deliver molecular cargoes between the nucleus and the surrounding cytoplasm.
In contrast to prevailing views, the team led by Prof. Roderick Lim, Argovia Professor at the Biozentrum and the Swiss Nanoscience Institute of the University of Basel, has now demonstrated that the nuclear pore complex does not work like a simple filter that regulates the nuclear transport process. Rather, different importins cooperate to continuously open and close the pore like a “revolving door”.
Importins regulate nuclear pores
For a long time scientists have reasoned that a molecular filter within the nuclear pore complex prevents or enables the passage of molecules into the nucleus. Lim’s current study now shows that this filter alone is not sufficient for barrier function but provides only the basic infrastructure for establishing one. Instead, cargo-carrying importins function as bona fide components that regulate the nuclear pore complex transport barrier.
Moreover, Lim and colleagues show how the shuttling of importins is coupled to their barrier function. In fact, importins exist in two interacting forms: alpha and beta. Importin beta promotes cargo access into the pore whereas Importin alpha determines the cargo that can enter the nucleus.
Surprisingly, the team has now discovered that importin alpha acts as a molecular switch that helps to release or retain importin beta to open or close the pore. In the absence of importin alpha, importin beta loses its ability to shuttle through the nuclear pore channel.
Importins in health and disease
The insights provided by the study also have implications for the understanding of diseases associated with transport defects at the nuclear pore complex, such as cancer.
“We always thought of the nuclear pore complex as a standalone machine that controls nuclear transport”, says Lim.
“Now, we have a much greater appreciation for how the systematic interplay of importin alpha and beta are able to regulate the nuclear pore complex to sustain continuous transport. Hence, if importin alpha malfunctions the revolving door mechanism might get stuck such that essential proteins cannot get to their nuclear destinations. Or if importin beta is defective, the pore might become leaky against unwanted substances that can enter and poison the nucleus.”
Larisa E. Kapinos, Binlu Huang, Chantal Rencurel and Roderick Y.H. Lim
Karyopherins regulate nuclear pore complex barrier and transport function
Journal of Cell Biology (2017), doi: 10.1083/jcb.201702092
Prof. Dr. Roderick Lim, University of Basel, Biozentrum, and Swiss Nanoscience Institute, Tel. +41 61 207 20 83, E-Mail: email@example.com
Heike Sacher, University of Basel, Biozentrum, Communications, Tel. +41 61 207 14 49, email: firstname.lastname@example.org
Heike Sacher | Universität Basel
Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)
North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Life Sciences
23.03.2018 | Materials Sciences
23.03.2018 | Process Engineering