by Tanya Thomas on  July 27, 2010 at 11:03 AM Research News
 Why Cell 'Reproduction' Slows Down
Scientists have figured why yeast cells, and maybe even other organisms' cells, are not able to go on producing copies of themselves forever.

Yeast cells, much like our own cells, have a finite ability to reproduce themselves.

A 'mother' cell can only produce 20-30 'daughters' before it loses the ability to replicate and dies.

Multidrug resistance (MDR) proteins are best known for helping cancer cells expel anticancer drugs.

Rong Li and colleagues at the Stowers Institute for Medical Research in Kansas City, Missouri, found that yeast lacking certain MDR proteins have a shorter reproductive lifespan; they produce fewer daughter cells.

Yeast engineered to contain more of these pumps, however, can produce more daughters.

Li and her colleagues found that yeast division also results in an unequal distribution of MDR proteins.

The mother cell retains the original MDR proteins while the bud gets young, newly formed MDR proteins. Because the mother's supply is never replenished, she has to rely on the pool of MDR proteins that she's born with, Li says.

Over time these proteins decay. Some lose only part of their function; others may stop working altogether.

We started to get the idea that "maybe these proteins are what's limiting the lifespan of these cells," Li says.

The team tested the idea that if the loss of MDR proteins does contribute to ageing, then cells that can't make these proteins should have shorter lifespans.

MDR proteins help rid cells of toxins, so as they begin to fail, toxins could accumulate even faster.

The study "raises the intriguing possibility that a similar mode of regulation could influence stem-cell senescence during human ageing," Nature quoted Matt Kaeberlein, at the University of Washington Medical School in Seattle, who investigates longevity in yeast, worms and mice, as saying.

It might also help explain why cancer cells, many of which are stuffed with MDRs, are seemingly immortal.

The latest study is published today in Nature Cell Biology.

Source: ANI

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