The epithelial cells that line the surface of tissues form a tightly sealed barrier, with individual cells joined together by structures called apical junctional complexes (AJCs). However, embryonic epithelium undergoes multiple physical rearrangements over development. For example, early in the formation of the brain and spinal cord, a subset of epithelial cells fold inward to form a groove that ultimately develops into a ‘neural tube’.
Such changes are achieved through the physical constriction of the apical (upper) domains of selected epithelial cells, a process driven by a ring-shaped network of cables composed of actin and myosin protein that are anchored at the AJCs. Now, work from Masatoshi Takeichi and postdoctoral fellow Takashi Ishiuchi of the RIKEN Center for Developmental Biology in Kobe has revealed an unexpected role for a protein named Willin in regulating this constriction.
Willin was previously assumed to act primarily as the mammalian equivalent of Expanded, a fruit fly protein that regulates growth. “It turned out that Willin localizes along cell junctions,” says Takeichi, “and we got interested in what it was doing there.”
They determined that Willin associates with a pair of proteins—Par3 and atypical protein kinase C (aPKC)—that help epithelial cells maintain their polarity, with clearly defined apical (top) and basal (bottom) segments. Willin and Par3 both seem to execute highly similar functions: they bind to and shepherd aPKC to AJCs, where aPKC acts to inhibit actomyosin-mediated constriction.
Since aPKC is an enzyme that regulates the function of other proteins by tagging them with chemical modifications, Takeichi and Ishiuchi searched for potential targets. Proteins known as Rho-associated kinases (ROCKs) localize to AJCs and modulate the function of actomyosin fibers, and the researchers confirmed that the ROCKs are direct targets of aPKC. The presence of unmodified ROCK at AJCs appears to promote apical constriction; however, after delivery of aPKC to the AJC, it inhibits constriction by modifying ROCK and triggering its release into the cytoplasm. “This was really an unexpected discovery,” says Takeichi.
These results show that Willin is an important regulator of epithelial cell shape, but Takeichi is not ready to discard the possibility that it may still perform functions that echo those of its cousin, Expanded. “Growth control and junctional contraction might be physiologically linked,” suggests Takeichi. “A future goal would be to clarify whether vertebrate Willin is involved in growth control and, if so, how this relates to its ability to induce epithelial apical constriction.”
The corresponding author for this highlight is based at the Laboratory for Cell Adhesion and Tissue Patterning, RIKEN Center for Developmental Biology
Ishiuchi, T. & Takeichi, M. Willin and Par3 cooperatively regulate epithelial apical constriction through aPKC-mediated ROCK phosphorylation. Nature Cell Biology 13, 860–866 (2011)
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences