Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How Old Yeast Cells Send Off Their Daughter Cells without the Baggage of Old Age

28.11.2011
The accumulation of damaged protein is a hallmark of aging that not even the humble baker’s yeast can escape. Yet, aged yeast cells spawn off youthful daughter cells without any of the telltale protein clumps. Now, researchers at the Stowers Institute for Medical Research may have found an explanation for the observed asymmetrical distribution of damaged proteins between mothers and their youthful daughters.

Reporting in the November 23, 2011, issue of Cell the research team, led by Stowers investigator Rong Li, Ph.D., proposes that the limited mobility of clumps of damaged proteins and yeast cells’ geometry—the narrowness of the connection (bud neck) between the mother and the daughter before their separation, in particular—are sufficient to ensure that protein aggregates accumulated during the normal aging process are retained in the mother cell during cell division.


Cell (Nov. 23, 2011)
Image: Courtesy of Chuankai Zhou, Stowers Institute for Medical Research
The movements of protein aggregates found in old yeast cells follow a "random walk" pattern.

“Harmful protein aggregates had recently been thought to be sent back into the mother cell via a directed transport system,” says Li. “Our model suggests that no active shuttle mechanism may be necessary to help with the asymmetric segregation of protein aggregates during yeast cell divisions.”

In the budding yeast Saccharomyces cerevisae—an important model organisms used in aging research—lifespan can be defined by the number of daughter cells a mother has produced, as opposed to by calendar time, a process known as replicative aging. Daughter cells reset their clock and start counting the number of cell division they have undergone from scratch.

The transition from youth to old age is accompanied by metabolic changes and the accumulation of damage as a result of wear and tear. A central question in aging research is the nature of the damage that contributes to aging and how old mother cells avoid passing on these aging determinants to their daughters.

One factor that is known to correlate with replicative age is the buildup of aggregates formed by damaged proteins. “These proteins are preferentially retained by the mother during bud formation and cell division,” explains Li. “A better understanding of replicative aging of a cell population based on asymmetric cell divisions may provide insights into how higher organisms maintain a population of “youthful” stem cells with high proliferative potential during aging.“

To learn more about the movement and fate of damaged proteins in dividing yeast cells, graduate student and first author Chuankai Zhou with help from Amr Eldakak, Ph.D, a postdoctoral research associate in the Li laboratory, added a green fluorescent tag to Hsp104p, a protein known to modify and dissolve protein aggregates by unfolding and refolding proteins. Zhou then used live-cell imaging to record the movements of thousands of protein aggregates induced by heat in three dimensions.

“Most movements were confined within the bud or the mother but we did see a few movements from bud to mother and vice versa,” says Zhou. “Overall though, we couldn’t detect any directionality in the movements of the aggregates.” In order to rigorously characterize the movement of the protein aggregates, Zhou collaborated with Stowers Research advisors Brian Slaughter, Ph.D., and Jay Unruh, Ph.D., and used particle tracking and computational analysis to show that the aggregate movement is best described as ‘random walk’.

Time-lapse movies also revealed that, over time, heat shock-induced aggregates cleared from all buds and their numbers plummeted in mother cells. When Zhou introduced a mutation into Hsp104p that does not affect Hsp104p’s ability to bind to protein aggregates but disrupts its refolding activity, aggregates no longer cleared from neither mother nor daughter cell. “It told us that heat-induced aggregates dissolved with the help of Hsp104p,” explains Zhou.

Zhou then turned his attention to naturally occurring protein aggregates, which are the result of oxidative damage in cells of older replicative age. He found that these protein clumps followed the same random walk pattern but didn’t dissolve over time. However, these aggregates appeared to move within the confines of the mother without escaping into the bud.

With the help of Stowers research advisor Boris Rubinstein, the team used 3D numerical simulations as well as a 1D analytical model to show that the limited, random mobility of the aggregates was sufficient to explain their preferential retention in the mother, and that the narrow opening of the bud neck further helps trapping the aggregates within the mother prior to cell division.

The research was supported primarily by a grant from the National Institute of Health.

About the Stowers Institute for Medical Research

The Stowers Institute for Medical Research is a non-profit, basic biomedical research organization dedicated to improving human health by studying the fundamental processes of life. Jim Stowers, founder of American Century Investments, and his wife Virginia opened the Institute in 2000. Since then, the Institute has spent over 800 million dollars in pursuit of its mission.

Currently the Institute is home to over 500 researchers and support personnel; over 20 independent research programs; and more than a dozen technology development and core facilities. Learn more about the Institute at www.stowers.org.

Gina Kirchweger | Newswise Science News
Further information:
http://www.stowers.org

More articles from Life Sciences:

nachricht Tag it EASI – a new method for accurate protein analysis
19.06.2018 | Max-Planck-Institut für Biochemie

nachricht How to track and trace a protein: Nanosensors monitor intracellular deliveries
19.06.2018 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Carbon nanotube optics provide optical-based quantum cryptography and quantum computing

19.06.2018 | Physics and Astronomy

How to track and trace a protein: Nanosensors monitor intracellular deliveries

19.06.2018 | Life Sciences

New material for splitting water

19.06.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>