Featured Research

from universities, journals, and other organizations

Scientists Unlock Molecular Mechanism That Controls Cell Growth

Date:
April 10, 2001
Source:
Northwestern University
Summary:
Scientists at Northwestern University have identified a molecular switch that controls when and how cells grow. A team led by Richard I. Morimoto, John Evans Professor of Biology, has shown that the cell shuts down when stressed and doesn’t divide until the environment is right again.

EVANSTON, Ill. — Scientists at Northwestern University have identified a molecular switch that controls when and how cells grow. A team led by Richard I. Morimoto, John Evans Professor of Biology, has shown that the cell shuts down when stressed and doesn’t divide until the environment is right again. These findings were published in the March 2001 issue of the journal Nature Cell Biology.

Related Articles


In order for living organisms to thrive, cells need to know when to grow. Environmental and physiological stress, such as that produced by toxins, a virus infection or poor nutrition, create an unhealthy environment at the molecular level. Cell growth under such conditions can result in serious problems, such as mistakes in chromosome replication or the beginnings of cancer.

"How does a cell know when its environment is bad?" said Morimoto. "It’s been known for centuries that stress has a negative effect on the development and growth of organisms, but until now, we didn’t know the mechanism that ties stress together with when and how cells grow."

It turns out that the signal transduction pathway, or the cascade of signals that leads to gene transcription and cell growth, is negatively regulated by a heat-shock protein called Hsp70, which acts as a stress sensor.

The protein — an ancient protein found in nearly every organism on Earth — patrols the cell’s immediate environment, in its role as constant protector. When biochemical stress builds to an unhealthy level, Hsp70 expression is rapidly activated and accumulates to high levels. The researchers showed that Hsp70 halts cell growth by binding to the protein Bag1.

In a healthy environment, Hsp70 keeps out of the way, allowing Bag1 to bind to a different protein, Raf-1, which sets the cell growth signalling process in motion. But when Bag1 is bound to Hsp70 during stressful times, it cannot bind to Raf-1 as well. When the stress ends and the numbers of Hsp70 return to normal, cell growth can continue.

"We wanted to determine if Bag1 and Hsp70 could be the source of the ongoing talk that monitors a cell’s environment and controls the growth state of a cell," said Morimoto, who cloned Hsp70 in 1985 and has been studying Bag1 for four years.

To assess the relationship between Hsp70 and Bag1, Morimoto’s team used mutants of the two proteins. Their results showed that Bag1 mutants defective in binding to Hsp70 stimulated Raf-1 and the signalling pathway, despite the fact that the numbers of Hsp70 were elevated, due to stress. They also showed that overexpressed Hsp70 mutants defective in binding to Bag1 had no effect on Raf-1 activity and cell growth. In the process, they identified the binding site on Hsp70 of Bag1.

These results indicate that the inhibitory effects of Hsp70 on the signalling pathway and cell growth require Bag1. The researchers also were able to show that only Bag1 was able to activate the signalling pathway leading to DNA synthesis, evidence that the pathway is extraordinarily selective.

Essentially, with Hsp70 and Raf-1 competing for binding to Bag1 two scenarios result: Hsp70 wins in an unhealthy and stressed environment, shutting down cell growth, and Raf-1 wins under healthy conditions, allowing cell growth.

"The identification of Hsp70 as a switch regulating Bag1 and activation of the signal transduction pathway provides scientists with a molecular framework to begin to understand the negative effects of stress on cell growth," said Morimoto.

Other authors on the paper are Jaewhan Song, who was a graduate student, and Masahiro Takeda, who was a postdoctoral fellow, at the time the research was done.

The research was supported by the National Institutes of General Medical Sciences and the Carol and Martin Gollub Foundation.


Story Source:

The above story is based on materials provided by Northwestern University. Note: Materials may be edited for content and length.


Cite This Page:

Northwestern University. "Scientists Unlock Molecular Mechanism That Controls Cell Growth." ScienceDaily. ScienceDaily, 10 April 2001. <www.sciencedaily.com/releases/2001/04/010410085217.htm>.
Northwestern University. (2001, April 10). Scientists Unlock Molecular Mechanism That Controls Cell Growth. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2001/04/010410085217.htm
Northwestern University. "Scientists Unlock Molecular Mechanism That Controls Cell Growth." ScienceDaily. www.sciencedaily.com/releases/2001/04/010410085217.htm (accessed October 25, 2014).

Share This



More Mind & Brain News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Academic Scandal Shocks UNC

Academic Scandal Shocks UNC

AP (Oct. 23, 2014) A scandal involving bogus classes and inflated grades at the University of North Carolina was bigger than previously reported, a new investigation found. (Oct. 23) Video provided by AP
Powered by NewsLook.com
Working Mother Getaway: Beaches Turks & Caicos

Working Mother Getaway: Beaches Turks & Caicos

Working Mother (Oct. 22, 2014) Feast your eyes on this gorgeous family-friendly resort. Video provided by Working Mother
Powered by NewsLook.com
What Your Favorite Color Says About You

What Your Favorite Color Says About You

Buzz60 (Oct. 22, 2014) We all have one color we love to wear, and believe it or not, your color preference may reveal some of your character traits. In celebration of National Color Day, Krystin Goodwin (@kyrstingoodwin) highlights what your favorite colors may say about you. Video provided by Buzz60
Powered by NewsLook.com
First-Of-Its-Kind Treatment Gives Man Ability To Walk Again

First-Of-Its-Kind Treatment Gives Man Ability To Walk Again

Newsy (Oct. 21, 2014) A medical team has for the first time given a man the ability to walk again after transplanting cells from his brain onto his severed spinal cord. Video provided by Newsy
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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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