Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dynamic duo takes out the cellular trash

08.09.2014

Salk scientists identify how immune cells use two critical receptors to clear dead cells from the body, pointing the way to new autoimmune and cancer therapies

In most of the tissues of the body, specialized immune cells are entrusted with the task of engulfing the billions of dead cells that are generated every day. When these garbage disposals don't do their job, dead cells and their waste products rapidly pile up, destroying healthy tissue and leading to autoimmune diseases such as lupus and rheumatoid arthritis.


In an inflammatory environment (left) and normal environment (right) macrophages (green) engulf dead cells (pink).

Credit: Anna Zagorska and Matt Joens, Waitt Advanced Biophotonics Center, Salk Institute

Now, Salk scientists have discovered how two critical receptors on these garbage-eating cells identify and engulf dead cells in very different environments, as detailed today in Nature Immunology.

"To target these receptors as treatments for autoimmune disease and cancer, it's important to know exactly which receptor is doing what. And this discovery tells us that," says senior author of the work Greg Lemke, Salk professor of molecular neurobiology and the holder of Salk's Françoise Gilot-Salk Chair.

The garbage-disposing cells, known as macrophages, have arrays of receptors on their surface, two of which—called Mer and Axl—are responsible for recognizing dead cells in normal environments and inflamed environments, respectively. Mer operates as a "steady-as-she-goes" receptor, clearing out dead cells in healthy tissues on a daily basis. Axl, in contrast, acts as an "all-hands-on-deck" receptor, kicking macrophages into action in inflammatory settings that result from infection or tissue trauma. These inflamed environments have many more dead cells.

"We thought Axl and Mer were doing the same job, and they are: they both recognize a so-called 'eat me' signal displayed on the surface of dead cells. But it turns out that they work in very different settings," says Lemke, whose lab first discovered the two receptors—which, along with a third, make up the TAM family—two decades ago. Lemke and colleagues explored the roles of TAM receptors in the brain initially, but observed that the absence of these receptors had dramatic effects on the immune system, including the development of autoimmune disease.

The receptors have since become a growing focus for cancer and autoimmune research, and previous work has found that these three receptors are important in other areas, including the intestines, reproductive organs and vision.

"This basic research focus allowed us to discover a completely new aspect of immune regulation that no one—including any immunologist—had known about before," adds Lemke.

In the new work, the researchers found multiple critical differences between Axl and Mer. For example, the receptors use different molecules—called ligands—to be activated: Axl has a single such ligand and, once engaged, is quickly cleaved off of the surface of the macrophage. Levels of the free-floating Axl in the blood have turned out to be an accurate, general biomarker for inflammation, quickly showing up in the circulation after tissue trauma or injury.

"We compared the behavior and regulation of the receptors, and the results were very striking," says first author Anna Zagórska. "In response to many different pro-inflammatory stimuli, Axl was upregulated and Mer was not. In contrast, immunosuppressive corticosteroids, which are widely used to suppress inflammation in people, upregulated Mer and suppressed Axl. These differences were our entry point to the study."

Next, the researchers are looking into each receptor's activity in more detail. The team is finding that these receptors are unusual in that they have a three-step binding procedure, whereas most cell receptors bind in one step. Exploring and understanding this process will help to lead to more targeted therapeutics for cancers and other diseases in which the receptors are thought to act.

###

Authors on the paper include Anna Zagórska, Paqui Través, Erin Lew, Ian Dransfield and Greg Lemke.

The work was funded by the National Institutes of Health, the Leona M. and Harry B. Helmsley Charitable Trust, the Nomis Foundation, the H.N. and Frances C. Berger Foundation, the Fritz B. Burns Foundation, the HKT Foundation, the Human Frontiers Science Program, and the Leukemia and Lymphoma Society.

About the Salk Institute for Biological Studies

The Salk Institute for Biological Studies is one of the world's preeminent basic research institutions, where internationally renowned faculty probes fundamental life science questions in a unique, collaborative, and creative environment. Focused both on discovery and on mentoring future generations of researchers, Salk scientists make groundbreaking contributions to our understanding of cancer, aging, Alzheimer's, diabetes and infectious diseases by studying neuroscience, genetics, cell and plant biology, and related disciplines.

Faculty achievements have been recognized with numerous honors, including Nobel Prizes and memberships in the National Academy of Sciences. Founded in 1960 by polio vaccine pioneer Jonas Salk, MD, the Institute is an independent nonprofit organization and architectural landmark.

Salk Communications | Eurek Alert!
Further information:
http://www.salk.edu

Further reports about: Dynamic Foundation Salk TAM autoimmune differences diseases environments healthy immune inflammation leading macrophages

More articles from Life Sciences:

nachricht Not of Divided Mind
19.01.2017 | Hertie-Institut für klinische Hirnforschung (HIH)

nachricht CRISPR meets single-cell sequencing in new screening method
19.01.2017 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>