[GRG] cells don’t necessarily degrade their own mitochondria

http://ift.tt/1sjDUZO
=8c9e493b-8a7d-4e4a-babc-d71d83d040ac

Some neurons transfer unwanted mito’s to astrocytes for disposal.

Transcellular degradation of axonal mitochondria

Chung-ha O. Davisa,b,
Keun-Young Kimc,
Eric A. Bushongc,
Elizabeth A. Millsa,b,
Daniela Boassac,
Tiffany Shihc,
Mira Kinebuchic,
Sebastien Phanc,
Yi Zhoub,
Nathan A. Bihlmeyerb,
Judy V. Nguyena,b,
Yunju Jina,
Mark H. Ellismanc,1, and
Nicholas Marsh-Armstronga,b,1,2

Significance

Mitochondria are organelles that perform many essential functions,
including providing the energy to cells. Cells remove damaged
mitochondria through a process called mitophagy. Mitophagy is
considered a subset of a process called autophagy, by which damaged
organelles are enwrapped and delivered to lysosomes for
degradation. Implicit in the categorization of mitophagy as a
subset of autophagy, which means “self-eating,” is the assumption
that a cell degrades its own mitochondria. However, we show here
that in a location called the optic nerve head, large numbers of
mitochondria are shed from neurons to be degraded by the lysosomes
of adjoining glial cells. This finding calls into question the
assumption that a cell necessarily degrades its own organelles.

Abstract

It is generally accepted that healthy cells degrade their own
mitochondria. Here, we report that retinal ganglion cell axons of
WT mice shed mitochondria at the optic nerve head (ONH), and that
these mitochondria are internalized and degraded by adjacent
astrocytes. EM demonstrates that mitochondria are shed through
formation of large protrusions that originate from otherwise
healthy axons. A virally introduced tandem fluorophore protein
reporter of acidified mitochondria reveals that acidified axonal
mitochondria originating from the retinal ganglion cell are
associated with lysosomes within columns of astrocytes in the ONH.
According to this reporter, a greater proportion of retinal
ganglion cell mitochondria are degraded at the ONH than in the
ganglion cell soma. Consistently, analyses of degrading DNA reveal
extensive mtDNA degradation within the optic nerve astrocytes, some
of which comes from retinal ganglion cell axons. Together, these
results demonstrate that surprisingly large proportions of retinal
ganglion cell axonal mitochondria are normally degraded by the
astrocytes of the ONH. This transcellular degradation of
mitochondria, or transmitophagy, likely occurs elsewhere in the
CNS, because structurally similar accumulations of degrading
mitochondria are also found along neurites in superficial layers of
the cerebral cortex. Thus, the general assumption that neurons or
other cells necessarily degrade their own mitochondria should be
reconsidered.

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About Johnny Adams

My full-time commitment is to slow and ultimately reverse age related functional decline to increase healthy years of life. I’ve been active in this area since the 1970s, steadily building skills and accomplishments. I have a good basic understanding of the science of aging, and have many skills that complement those of scientists so they can focus on science to advance our shared mission. Broad experience Top skills: administration, management, information technology (data and programming), communications, writing, marketing, market research and analysis, public speaking, forging ethical win-win outcomes among stakeholders (i.e. high level "selling"). Knowledge in grant writing, fundraising, finance. Like most skilled professionals, I’m best described as a guy who defines an end point, then figures out how to get there. I enjoy the conception, design, execution and successful completion of a grand plan. Executive Director Gerontology Research Group (GRG). Manages Email discussion forum, web site, meetings and oversees supercentenarian (oldest humans, 110+ years) research. CEO / Executive Director Carl I. Bourhenne Medical Research Foundation (Aging Intervention Foundation), an IRS approved 501(c)(3) nonprofit. http://www.AgingIntervention.org Early contributor to Supercentenarian Research Foundation. Co-Founder Geroscience Healthspan Forum. Active contributor to numerous initiatives to increase healthy years of life. Co-authored book on conventional, practical methods available today to slow the processes of aging – nutrition, exercise, behavior modification and motivation, stress reduction, proper supplementation, damage caused by improper programs, risk reduction and others. Fundamental understanding of, and experience in the genomics of longevity (internship analyzing and curating longevity gene papers). Biological and technical includes information technology, software development and computer programming, bioinformatics and protein informatics, online education, training programs, regulatory, clinical trials software, medical devices (CAT scanners and related), hospital electrical equipment testing program. Interpersonal skills – good communication, honest, well liked, works well in teams or alone. Real world experience collaborating in interdisciplinary teams in fast paced organizations. Uses technology to advance our shared mission. Education: MBA 1985 University of Southern California -- Deans List, Albert Quon Community Service Award (for volunteering with the American Longevity Association and helping an elderly lady every other week), George S. May Scholarship, CA State Fellowship. BA psychology, psychobiology emphasis 1983 California State University Fullerton Physiological courses as well as core courses (developmental, abnormal etc). UCLA Psychobiology 1978, one brief but fast moving and fulfilling quarter. Main interest was the electrochemical basis of consciousness. Also seminars at the NeuroPsychiatric Institute. Other: Ongoing conferences, meetings and continuing education. Aging, computer software and information technology. Some molecular biology, biotech, bio and protein informatics, computer aided drug design, clinical medical devices, electronics, HIPAA, fundraising through the Assoc. of Fundraising Professionals. Previous careers include: Marketing Increasing skill set and successes in virtually all phases, with valuable experience in locating people and companies with the greatest need and interest in a product or service, and sitting across the table with decision makers and working out agreements favorable to all. Information Technology: Management, data analysis and programming in commercial and clinical trials systems, and bioinformatics and protein informatics. As IT Director at Newport Beach, CA based technology organization Success Family of Continuing Education Companies, provided online software solutions for insurance and financial professionals in small to Fortune 500 size companies. We were successful with lean team organization (the slower moving competition was unable to create similar software systems). Medical devices: At Omnimedical in Paramount CA developed and managed quality assurance dept. and training depts. for engineers, physicians and technicians. Designed hospital equipment testing program for hospital services division. In my early 20’s I was a musician, and studied psychology and music. Interned with the intention of becoming a music therapist. These experiences helped develop valuable skills used today to advance our shared mission of creating aging solutions.
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