Featured Research

from universities, journals, and other organizations

Getting rid of old mitochondria: Some neurons turn to neighbors to help take out the trash

Date:
June 16, 2014
Source:
University of California, San Diego Health Sciences
Summary:
It’s broadly assumed that cells degrade and recycle their own old or damaged organelles, but researchers have now 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.

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.

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."

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).


Story Source:

The above story is based on materials provided by University of California, San Diego Health Sciences. Note: Materials may be edited for content and length.


Journal Reference:

  1. Chung-ha O. Davis, Keun-Young Kim, Eric A. Bushong, Elizabeth A. Mills, Daniela Boassa, Tiffany Shih, Mira Kinebuchi, Sebastien Phan, Yi Zhou, Nathan A. Bihlmeyer, Judy V. Nguyen, Yunju Jin, Mark H. Ellisman, and Nicholas Marsh-Armstrong. Transcellular degradation of axonal mitochondria. PNAS, June 16, 2014 DOI: 10.1073/pnas.1404651111

Cite This Page:

University of California, San Diego Health Sciences. "Getting rid of old mitochondria: Some neurons turn to neighbors to help take out the trash." ScienceDaily. ScienceDaily, 16 June 2014. <www.sciencedaily.com/releases/2014/06/140616203941.htm>.
University of California, San Diego Health Sciences. (2014, June 16). Getting rid of old mitochondria: Some neurons turn to neighbors to help take out the trash. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2014/06/140616203941.htm
University of California, San Diego Health Sciences. "Getting rid of old mitochondria: Some neurons turn to neighbors to help take out the trash." ScienceDaily. www.sciencedaily.com/releases/2014/06/140616203941.htm (accessed September 20, 2014).

Share This



More Health & Medicine News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could Grief Affect The Immune Systems Of Senior Citizens?

Could Grief Affect The Immune Systems Of Senior Citizens?

Newsy (Sep. 19, 2014) The study found elderly people are much more likely to become susceptible to infection than younger adults going though a similar situation. Video provided by Newsy
Powered by NewsLook.com
Jury Delivers Verdict in Salmonella Trial

Jury Delivers Verdict in Salmonella Trial

AP (Sep. 19, 2014) A federal jury has convicted three people in connection with an outbreak of salmonella poisoning five years ago that sickened hundreds of people and was linked to a number of deaths. (Sept. 19) Video provided by AP
Powered by NewsLook.com
How The 'Angelina Jolie Effect' Increased Cancer Screenings

How The 'Angelina Jolie Effect' Increased Cancer Screenings

Newsy (Sep. 19, 2014) Angelina's Jolie's decision to undergo a preventative mastectomy in 2013 inspired many women to seek early screenings for the disease. Video provided by Newsy
Powered by NewsLook.com
The Cost of Ebola

The Cost of Ebola

Reuters - Business Video Online (Sep. 18, 2014) As Sierra Leone prepares for a three-day "lockdown" in its latest bid to stem the spread of Ebola, Ciara Lee looks at the financial implications of fighting the largest ever outbreak of the disease. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins