A new starring role for astrocytes
Figure 1: Healthy astrocytes send separate signals through each process, while astrocytes in neurological disorders send synchronous signals to their entire network. © 2012 Katsuhiko Mikoshiba, Misa Arizono and Hiroko Bannai, RIKEN Brain Science Institute
Astrocytes, previously thought of as helper cells for neurons, have recently been shown to send signals themselves. The signals are chemical not electrical and astrocytes send them to neurons, vascular cells and other astrocytes to improve the efficiency of synaptic signaling. A team led by Katsuhiko Mikoshiba and Hiroko Bannai at the RIKEN Brain Science Institute, Wako, have described the mechanism that allows astrocytes to signal each cell in their network individually.
Named for their star-like shape, astrocytes have a central ‘soma’ and many ray-like arms connecting to the cells they regulate. Healthy astrocytes send separate Ca2+ signals through each ray, called a ‘process’. Signaling was known to be regulated by a receptor in the cellular membrane called the metabotropic glutamate receptor (mGluR5), but it was unclear how the signals were confined to individual processes. Understanding this specificity may be therapeutically important because in brains affected with Alzheimer’s disease or epilepsy astrocytes send global signals, more like a megaphone broadcast than the telephone calls made by healthy astrocytes (Fig. 1).
To understand how astrocyte signaling is regulated, the researchers tagged individual mGluR5 receptors with quantum dots—semiconductor nano-crystals that emit light when excited—then observed how the receptors migrated through the fluid membrane. Video footage revealed that receptors did not pass from the process to the soma. In normal astrocytes, the mGluR5-selective diffusion barrier could, by compartmentalization of Ca2+ signaling, allow each process to regulate its contacting partners independently.
To investigate the character of the barrier, Mikoshiba’s team attempted to undermine it. Over-expression of mGluR5 overwhelmed the barrier, which they infer is made of proteins that interact with the cytosolic portion of mGluR5. Each barrier protein pairs with a single mGluR5 molecule and prevents it from crossing to the soma. However, the number of barrier proteins is finite and an overabundance of mGluR5 leaves some receptors free to cross into the soma, thus enabling propagation of global signals through every process in the astrocyte.
Experimental models of Alzheimer’s disease and epilepsy have shown increased concentrations of mGlu5 in astrocytes. The researchers believe that understanding the molecular nature of the diffusion barrier will provide new targets for the treatment of these conditions. Once they reveal the molecular nature of the barrier, the team hopes to produce a transgenic mouse lacking the astrocytic barrier protein. “We are very curious to know the effect of global astrocytic Ca2+ signaling on the neuronal network and neuro-vascular coupling,” says Mikoshiba.
More information: Arizono, M., Bannai, H., Nakamura, K., Niwa, F., Enomoto, M., Matsu-ura, T., Miyamoto, A., Sherwood, M.W., Nakamura, T. & Mikoshiba, K. Receptor-selective diffusion barrier enhances sensitivity of astrocytic processes to metabotropic glutamate receptor stimulation. Science Signaling 5, ra27 (2012). stke.sciencemag.or… s;5/218/ra27
Journal reference: Science Signaling
Provided by RIKEN
- New brain cells implicated in machinery of cannabinoid signaling Mar 26, 2008 | not rated yet | 0
- Astrocytes found to bridge gap between global brain activity and localized circuits May 11, 2012 | not rated yet | 0
- Astrocytes affect brain's information signaling Jun 14, 2010 | not rated yet | 0
- Alzheimer's-associated plaques may have impact throughout the brain Feb 26, 2009 | not rated yet | 0
- HIV disrupts blood-brain barrier Jun 28, 2011 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
Ratio of Hydrogen of Oxygen in Dessicated Animal Protein
May 13, 2013 As an experiment, for the past few months I've been consuming at least one portion of Jell-O or unflavored Knox gelatin per day. I'm 64, in very...
Alcohol and acetaminophen
May 13, 2013 Edit: sorry for the typo in the title , can't edit I looked around on google quite a bit and it's very hard to find precise information on the...
Marie Curie's leukemia
May 13, 2013 Does anyone know what might be the cause of Marie Curie's cancer
- More from Physics Forums - Medical Sciences
More news stories
In their quest to learn more about the variability of cells between and within tissues, biomedical scientists have devised tools capable of simultaneously measuring dozens of characteristics of individual ...
Medical research 4 hours ago | 5 / 5 (1) | 0 |
In 2008 researchers from the University of Southern Denmark showed that the drug thioridazine, which has previously been used to treat schizophrenia, is also a powerful weapon against antibiotic-resistant bacteria such as ...
Medical research May 17, 2013 | 3.7 / 5 (3) | 0 |
Scientists investigating the interaction of a group of proteins in the brain responsible for protecting nerve cells from damage have identified a new target that could increase cell survival.
Medical research May 17, 2013 | 5 / 5 (1) | 0
New findings by researchers carrying out experiments at the U.S. Department of Energy Office of Science's Advanced Photon Source (APS) help explain why some drugs that interact with two kinds of human serotonin ...
Medical research May 17, 2013 | 4 / 5 (1) | 0 |
Researchers at the University of Wisconsin have identified a potential new risk factor for obstructive sleep apnea: asthma. Using data from the National Institutes of Health (Heart, Lung, and Blood Institute)-funded Wisconsin ...
3 hours ago | not rated yet | 0 |
A new study looking at sleep-disordered breathing (SDB) and markers for Alzheimer's disease (AD) risk in cerebrospinal fluid (CSF) and neuroimaging adds to the growing body of research linking the two.
3 hours ago | not rated yet | 0 |
The hunt for an HIV vaccine has gobbled up $8 billion in the past decade, and the failure of the most recent efficacy trial has delivered yet another setback to 26 years of efforts.
8 hours ago | not rated yet | 0
Scientists at Johns Hopkins have turned their view of osteoarthritis (OA) inside out. Literally. Instead of seeing the painful degenerative disease as a problem primarily of the cartilage that cushions joints, ...
4 hours ago | 5 / 5 (1) | 0 |
The devastating effect of Alzheimer's disease on bilingual people has been thrown into focus in Canada, where the sudden loss of a second language can leave sufferers feeling like strangers in their own country.
6 hours ago | not rated yet | 0
Gourmands and foodies everywhere have long recognized ginger as a great way to add a little peppery zing to both sweet and savory dishes; now, a study from researchers at Columbia University shows purified components of the ...
3 hours ago | not rated yet | 0