Source: Okayama University (JAPAN), Public Relations and Information Strategy
For immediate release: 25 March 2019
Okayama University research: Is too much protein a bad thing?

(Okayama, 25 March) In a recent study published in eLife scientists at Okayama show how proteins can hamper an organism’s growth.

Biochemists have shown that very high protein levels can be harmful to cells in the human body. However, exactly which proteins fall under this category remains a mystery. Mr.Yuichi Eguchi(graduate student) and Associate Professor Hisao Moriya’s research team at Okayama University recently reported a framework for discriminating between which proteins are toxic at excessive levels and which are not.

The theory behind this phenomenon, also known as the protein burden, is that accumulation of excessive protein within the cell will deplete the cell of resources, such as energy. The limit required to reach this burden though, is not the same for all proteins. Green fluorescent protein (GFP) is a harmless protein artificially introduced into cells for visualizing the insides of the cell. When GFP levels were increased within yeast cells, they found that GFP up to 15% of total protein content was harmless to the cells. Using this measure as a standard, Associate Professor Hisao Moriya’s team set out to estimate the burden limit of functional proteins in the cells. 29 proteins essential for energy production were subsequently over-produced.

While many of these proteins also had limits close to 15%, suggestive of their harmless nature, some of the proteins showed growth retardation and other unpleasant effects at lower levels. One such protein was found to accumulate within the mitochondria. Clogging the mitochondria prevents cells from producing oxygen. Another protein was found to undergo structural changes and aggregate into big pieces. Another reason for some of these proteins having a low burden limit, was due to metabolic disturbances induced when they were produced even slightly higher than usual. When these proteins were inactivated by mutations, their burden limit increased. Lastly, the researchers also found that certain proteins showed growth retardation, even at very low levels. Further investigation revealed that such proteins are programmed to remain at inherently low levels. Therefore, even small changes to their concentrations can be dangerous.

This study paved a framework for biologists to make distinctions between proteins based on how toxic they are when present in abnormal amounts. These differences could be attributed to the function, structure or genetic programming for that protein. Scientists can hope to use this framework to investigate proteins that are associated with diseases such as Alzheimer’s disease or Parkinson’s disease.


Background
The protein burden: Each protein has a distinct function within cells. Proteins are found in millions within the cell, and are synthesized or increased when required. Their levels subside when the cell doesn’t require them anymore. In certain conditions, such as neurodegenerative disorders, the levels of some proteins inherently remain high. Because the cell is not used to this, a battle to reduce these proteins ensues. This not only uses up the cell’s energy but damages the cell in the process.

Reference
Yuichi Eguchi、 Koji Makanae、 Tomohisa Hasunuma、 Yuko Ishibashi、 Keiji Kito、 Hisao Moriya. Estimating the protein burden limit of yeast cells by measuring the expression limits of glycolytic proteins. "eLIFE, 2018;7:e34595.
https://elifesciences.org/articles/34595

Reference (Okayama Univ. e-Bulletin & OU-MRU): Associate Professor Moriya’s team
e-Bulletin Vol.3 (2013)：Measuring the copy number limits of all genes in budding yeast. - First time ever for any organisms -.
OU-MRU Vol.36 (2017)：Overloading of protein localization triggers cellular defects.
OU-MRU Vol.37 (2017)：Protein dosage compensation mechanism unravelled.

Correspondence to
Associate Professor Hisao Moriya, Ph.D.
Research Core for Interdisciplinary Sciences, Okayama University,
3-1-1 Tsushimanaka, Kita-ku, Okayama 700-8530, Japan
e-mail : [email protected]
For inquiries, please contact us by replacing (a) with the @ mark.
http://tenure5.vbl.okayama-u.ac.jp/~hisaom/HMwiki/index.php?TopEnglish

Further information
Okayama University
1-1-1 Tsushima-naka , Kita-ku , Okayama 700-8530, Japan
Public Relations and Information Strategy
E-mail: www-adm (a) adm.okayama-u.ac.jp
For inquiries, please contact us by replacing (a) with the @ mark.
Website: www.okayama-u.ac.jp/index_e.html
Okayama Univ. e-Bulletin: www.okayama-u.ac.jp/user/kouhou/ebulletin/
About Okayama University (You Tube): https://www.youtube.com/watch?v=iDL1coqPRYI
Okayama University Image Movie (You Tube): https://www.youtube.com/watch?v=KU3hOIXS5kk

Okayama University Medical Research Updates （OU-MRU）
The whole volume : OU-MRU (1- )
Vol.1：Innovative non-invasive ‘liquid biopsy’ method to capture circulating tumor cells from blood samples for genetic testing
Vol.2：Ensuring a cool recovery from cardiac arrest
Vol.3：Organ regeneration research leaps forward
Vol.4：Cardiac mechanosensitive integrator
Vol.5：Cell injections get to the heart of congenital defects
Vol.6：Fourth key molecule identified in bone development
Vol.7：Anticancer virus solution provides an alternative to surgery
Vol.8：Light-responsive dye stimulates sight in genetically blind patients
Vol.9：Diabetes drug helps towards immunity against cancer
Vol.10：Enzyme-inhibitors treat drug-resistant epilepsy
Vol.11：Compound-protein combination shows promise for arthritis treatment
Vol.12：Molecular features of the circadian clock system in fruit flies
Vol.13：Peptide directs artificial tissue growth
Vol.14：Simplified boron compound may treat brain tumours
Vol.15：Metamaterial absorbers for infrared inspection technologies
Vol.16：Epigenetics research traces how crickets restore lost limbs
Vol.17：Cell research shows pathway for suppressing hepatitis B virus
Vol.18：Therapeutic protein targets liver disease
Vol.19：Study links signalling protein to osteoarthritis
Vol.20：Lack of enzyme promotes fatty liver disease in thin patients
Vol.21：Combined gene transduction and light therapy targets gastric cancer
Vol.22：Medical supportive device for hemodialysis catheter puncture
Vol.23：Development of low cost oral inactivated vaccines for dysentery
Vol.24：Sticky molecules to tackle obesity and diabetes
Vol.25：Self-administered aroma foot massage may reduce symptoms of anxiety
Vol.26：Protein for preventing heart failure
Vol.27：Keeping cells in shape to fight sepsis
Vol.28：Viral-based therapy for bone cancer
Vol.29：Photoreactive compound allows protein synthesis control with light
Vol.30：Cancer stem cells’ role in tumor growth revealed
Vol.31：Prevention of RNA virus replication
Vol.32：Enzyme target for slowing bladder cancer invasion
Vol.33：Attacking tumors from the inside
Vol.34：Novel mouse model for studying pancreatic cancer
Vol.35：Potential cause of Lafora disease revealed
Vol.36：Overloading of protein localization triggers cellular defects
Vol.37：Protein dosage compensation mechanism unravelled
Vol.38：Bioengineered tooth restoration in a large mammal
Vol.39：Successful test of retinal prosthesis implanted in rats
Vol.40：Antibodies prolong seizure latency in epileptic mice
Vol.41：Inorganic biomaterials for soft-tissue adhesion
Vol.42：Potential drug for treating chronic pain with few side effects
Vol.43：Potential origin of cancer-associated cells revealed
Vol.44：Protection from plant extracts
Vol.45：Link between biological-clock disturbance and brain dysfunction uncovered
Vol.46：New method for suppressing lung cancer oncogene
Vol.47：Candidate genes for eye misalignment identified
Vol.48：Nanotechnology-based approach to cancer virotherapy
Vol.49：Cell membrane as material for bone formation
Vol.50：Iron removal as a potential cancer therapy
Vol.51：Potential of 3D nanoenvironments for experimental cancer
Vol.52：A protein found on the surface of cells plays an integral role in tumor growth and sustenance
Vol.53：Successful implantation and testing of retinal prosthesis in monkey eyes with retinal degeneration
Vol.54：Measuring ion concentration in solutions for clinical and environmental research
Vol.55：Diabetic kidney disease: new biomarkers improve the prediction of the renal prognosis
Vol.56：New device for assisting accurate hemodialysis catheter placement
Vol.57：Possible link between excess chewing muscle activity and dental disease
Vol.58：Insights into mechanisms governing the resistance to the anti-cancer medication cetuximab
Vol.59：Role of commensal flora in periodontal immune response investigated
Vol.60：Role of commensal microbiota in bone remodeling
Vol.61：Mechanical stress affects normal bone development
Vol.62：3D tissue model offers insights into treating pancreatic cancer
Vol.63：Promising biomarker for vascular disease relapse revealed
Vol.64：Inflammation in the brain enhances the side-effects of hypnotic medication
Vol.65：Game changer: How do bacteria play Tag ?