Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Getting rid of old mitochondria

17.06.2014

Some neurons turn to neighbors to help take out the trash

It's broadly assumed that cells degrade and recycle their own old or damaged organelles, but researchers at University of California, San Diego School of Medicine, The Johns Hopkins University School of Medicine and Kennedy Krieger Institute have discovered that some neurons transfer unwanted mitochondria – the tiny power plants inside cells – to supporting glial cells called astrocytes for disposal.


Pictured is mouse optic nerve and retina, responsible for relaying information from the eye to the brain. The tissue has been fluorescently stained to reveal the distribution of astrocytes (yellow), retinal ganglion cell axons (purple), myelin (green) and nuclei (cyan). Retinal ganglion cell axons transfer mitochondria to adjacent astrocytes in the optic nerve head behind the retina. Astrocytes degrade the mitochondria in a process called transmitophagy.

Credit: Image courtesy of Mark Ellisman, NCMIR, UC San Diego.

The findings, published in the June 17 online Early Edition of PNAS, suggest some basic biology may need revising, but they also have potential implications for improving the understanding and treatment of many neurodegenerative and metabolic disorders.

"It does call into question the conventional assumption that cells necessarily degrade their own organelles. We don't yet know how generalized this process is throughout the brain, but our work suggests it's probably widespread," said Mark H. Ellisman, PhD, Distinguished Professor of Neurosciences, director of the National Center for Microscopy and Imaging Research (NCMIR) at UC San Diego and co-senior author of the study with Nicholas Marsh-Armstrong, PhD, in the Department of Neuroscience at Johns Hopkins University and the Hugo W. Moser Research Institute at Kennedy Krieger Institute in Baltimore.

"The discovery of a standard process for transfer of trash from neuron to glia will most likely be very important to understanding age-related declines in function of the brain and neurodegenerative or metabolic disorders," Marsh-Armstrong said. "We expect the impact to be significant in other areas of biomedicine as well."

The researchers looked specifically at the axons of retinal ganglion cells in mice, a type of neuron that transmits visual information from the eye to the brain. The investigation was prompted by observations by Marsh-Armstrong while studying a mouse model of glaucoma that protein products from the retina were accumulating in the optic nerve head (ONH) just behind the eye.

Using a combination of advanced microscopy and molecular techniques developed at the Ellisman and Marsh-Armstrong laboratories, they discovered that damaged mitochondria in retinal ganglion cells were shed at the ONH where ganglion cell axons exit the eye to form the optic nerve leading to the brain. These mitochondria were taken up and degraded by adjacent astrocytes, the most abundant form of glial cell in the vertebrate nervous system and the only cell which bridges between nerve cells and the brain's blood supply.

The discovery refutes the common assumption that all cells internally isolate, degrade and remove damaged materials – a process generally known as autophagy (Greek for "to self-eat"). When the process involves mitochondria, it's called mitophagy. The process described by Marsh-Armstrong, Ellisman and colleagues has been dubbed "transmitophagy."

The surprising findings still leave questions to be answered. For example, do the mitochondria removed at the ONH originate only from the population residing in the long conducting nerve fibers from the eye to the brain or are some actively transported from the retina itself?

Ellisman said the findings could potentially improve understanding – and perhaps eventually the treatment – of diverse disorders. "Mitochondria play prominent roles in the health of axons, which are fundamental to connecting neurons and transmitting information. It should be a priority to further explore what happens in transmitophagy and whether defects in this phenomenon contribute to neuronal dysfunction or disease."

###

Co-authors include Chung-ha O. Davis, Elizabeth A. Mills and Judy V. Nguyen, The Johns Hopkins University School of Medicine and Kennedy Krieger Institute; Keu-Young Kim, Eric A. Bushong, Daniela Boassa, Tiffany Shih, Mira Kinebuchi and Sebastien Phan, National Center for Microscopy and Imaging Research, UCSD; Yi Zhou, Kennedy Krieger Institute; Nathan A. Bihlmeyer and Yunju Jin, The Johns Hopkins University School of Medicine.

Funding for this research came, in part, from the National Institutes of Health (grants R01 EY022680 and R01 EY019960), the International Retinal Research Foundation, the Glaucoma Research Foundation, the Melza M. and Frank Theodore Barr Foundation, the National Center for Research Resources (grant 5P41RR004050), the National Institute on Drug Abuse Human Brain Project (grant DA016602), the National Institute of General Medical Sciences (grants 5R01GM82949 and 5P41GM103412-25), NIGMS training grant 5T32GM07814 and the National Science Foundation (grant DGE-1232825).

Scott LaFee | Eurek Alert!
Further information:
http://www.ucsd.edu

More articles from Health and Medicine:

nachricht Plasmonic biosensors enable development of new easy-to-use health tests
14.12.2017 | Aalto University

nachricht ASU scientists develop new, rapid pipeline for antimicrobials
14.12.2017 | Arizona State University

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>