Featured Research

from universities, journals, and other organizations

Decision Making At The Cellular Level

Date:
July 1, 2002
Source:
Johns Hopkins Medical Institutions
Summary:
It’s a wonder cells make it through the day with the barrage of cues and messages they receive and transmit to direct the most basic and necessary functions of life. Such cell communication, or signal transduction, was at least thought to be an "automatic" cascade of biochemical events. Now, however, a study reported in a recent issue of Nature by Johns Hopkins and Harvard scientists has found that even before a message makes it through the outer cell membrane to the inner nucleus, the cell is busy activating a molecular switch to guide how the message will be delivered in the first place.

It’s a wonder cells make it through the day with the barrage of cues and messages they receive and transmit to direct the most basic and necessary functions of life. Such cell communication, or signal transduction, was at least thought to be an "automatic" cascade of biochemical events. Now, however, a study reported in a recent issue of Nature by Johns Hopkins and Harvard scientists has found that even before a message makes it through the outer cell membrane to the inner nucleus, the cell is busy activating a molecular switch to guide how the message will be delivered in the first place.

Related Articles


"Our results add a layer of complexity to understanding how messages are communicated by cells," says Mark Donowitz, M.D., professor of medicine at Hopkins and a co-author of the study in the June 20 issue. "But by the same token, the new layer offers an exciting new aspect of cellular circuitry that could lead to potential therapies for many serious disorders," he says.

"This extra step in cell signaling actually lets the cell figure out how it’s going to communicate what it needs to," says Donowitz. "Without this switchboard system, the cell would go crazy and overload because every stimulus that passed by would be forwarded to its interior."

The two most common cellular signals are calcium and cyclic adenosine monophosphate, or cAMP. They are sometimes known as "second messengers" because they intercept messages from receptors on the cell surface and relay them to proteins within the cell, altering their shape and thus their behavior and that of the cell at large.

Donowitz and colleagues showed that a cell decides which signal to use, calcium or cAMP, by the presence or absence of a specific protein called sodium/hydrogen exchanger regulatory factor 2, or NHERF2. Specifically, their experiments tested how the receptor for parathyroid hormone, and for parathyroid hormone-related protein (also a hormone), on the cell surface signals the interior of the cell to perform specific functions. They found that the signal includes more than just the receptor and the proteins that latch onto it, but requires an additional class of proteins (of which NHERF2 is a member) called PDZ proteins that determine whether to send the signal via calcium or through cAMP. If NHERF2 is present along with the parathyroid hormone receptor, then the signal is sent via calcium. If there is no NHERF2, then cAMP is responsible for delivering the message.

The cell’s decision to use calcium or cAMP is important because each generates different responses from its target proteins, says Donowitz. For example, a signal relayed by cAMP might induce a kidney cell to release water or a bone cell to break down into its constituent minerals. Likewise, signals relayed by calcium could lead to the aggregation of blood platelets, which cause clots, or to the release of histamine, a major component of the allergic response.

"These results show that at the very earliest stage of cell signaling, called receptor binding, there is a switch that determines what kind of signal will be used," says Donowitz. "To understand cell signaling, you really have to know the whole system."

The receptor for parathyroid hormone, for example, is crucial for signaling and proper functioning of the parathyroid glands, intestinal cells and kidney cells. Parathyroid hormone and parathyroid hormone-related protein are vital to the normal functioning of the body. Disruptions in the regulation or amount of these substances can lead to serious ailments, including kidney stones, convulsions, decalcification of bones or "rubber bones," and can interfere with the normal growth of bones and cartilage. Common diseases that are caused in part by faulty signaling in cells include cancer, diabetes and disorders of the immune system.

Other authors of the study are C. Chris Yun of Hopkins, Matthew J. Mahon (lead author) and Gino V. Segre (senior author), both of Massachusetts General Hospital and Harvard Medical School.

M.J. Mahon, et al. Nature (2002) Na+/H+ exchanger regulatory factor 2 directs parathyroid hormone 1 receptor signalling. Vol. 417:858-861.

On the Web:

http://www.hopkinsmedicine.org/graduateprograms/cmm/donowitz.html


Story Source:

The above story is based on materials provided by Johns Hopkins Medical Institutions. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins Medical Institutions. "Decision Making At The Cellular Level." ScienceDaily. ScienceDaily, 1 July 2002. <www.sciencedaily.com/releases/2002/06/020627003257.htm>.
Johns Hopkins Medical Institutions. (2002, July 1). Decision Making At The Cellular Level. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2002/06/020627003257.htm
Johns Hopkins Medical Institutions. "Decision Making At The Cellular Level." ScienceDaily. www.sciencedaily.com/releases/2002/06/020627003257.htm (accessed October 25, 2014).

Share This



More Plants & Animals News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. 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


Plants & Animals

Earth & Climate

Fossils & Ruins

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