Stress signals link pre-existing sickness with susceptibility to bacterial infection

Jul 28, 2009

Mitochondrial diseases disrupt the power generating machinery within cells and increase a person's susceptibility to bacterial infection, particularly in the lungs or respiratory tract. A new study published in Disease Models & Mechanisms (DMM), shows that infection with the pneumonia causing bacteria Legionella, is facilitated by an increased amount of a signaling protein that is associated with mitochondrial disease.

Patients with exhibit a wide range of symptoms including diabetes, blindness, deafness, stroke-like episodes, epilepsy, ataxia, muscle weakness and kidney disease. The metabolic abnormalities that cause these effects also induce a stress signal intended to help the body overcome its energy deficit. The stress-signal induces the production of more mitochondria, the energy generating 'powerplants' of the body, in the hopes that more mitochondria will result in a better power supply. Researchers now show that the stress-signal associated with mitochondrial disease facilitates the growth and reproduction of the lung-infecting bacteria, Legionella.

with mitochondrial disease increase their production of a signaling protein called AMP-activated protein kinase (AMPK), to promote the generation of more energy producing mitochondria. Infectious bacteria, like Legionella, target the mitochondria and might use them to supplement their own needs and survival requirements. By manipulating AMPK levels, scientists were able to directly influence the ability of bacteria to replicate inside of the single-celled organism, Dictyostelium.

Striking similarities that exist between simple organisms like Dictyostelium and humans allow scientists to use them to understand human disease. Dictyostelium is a free-living amoeba whose rapid movements make it useful to study motility and energy regulation, and in this case, the association between energy regulation and susceptibility to infection. Like humans, Dictyostelium can be infected by Legionella and quickly responds by producing a host of metabolism-associated proteins. Another similarity between humans and Dictyostelium is that both use AMPK as an internal sensor to coordinate energy synthesis with energy needs. However, unlike humans, researchers can infect Dictyostelium with germs like Legionella in a controlled environment and determine the influence of various parameters on the course of infection.

More information: The report titled 'Legionella pneumophila multiplication is enhanced by chronic AMPK signalling in mitochondrially diseased cells' was written by Lisa Francione, Paige K. Smith, Sandra L. Accari, Paul B. Bokko and Paul Fisher at La Trobe Univeristy in Australia, Salvatore Bozzaro at University of Turin in Italy and Phillip E Taylor and Peter L. Beech at Deakin University in Australia. The study is published in the September/October 2009 issue of the new research journal, Disease Models & Mechanisms (DMM), dmm.biologists.org/ .

Source: The Company of Biologists (news : web)

Explore further: Breakthrough in understanding of important blood protein

add to favorites email to friend print save as pdf

Related Stories

Power-boosting signal in muscle declines with age

Feb 06, 2007

As people age, they may have to exercise even harder to get the benefits afforded to younger folk. That's the suggestion of a report in the February issue of the journal Cell Metabolism, published by Cell Press, showing that a ...

Legionnaire's bacterial proteins work together to survive

Oct 23, 2007

Proteins within the bacteria that cause Legionnaire’s disease can kidnap their own molecular “coffin” and carry it to a safe place within the cell, ensuring their survival, Yale School of Medicine researchers report ...

White Blood Cell Uses DNA 'Catapult' to Fight Infection

Aug 13, 2008

(PhysOrg.com) -- U.S. and Swiss scientists have made a breakthrough in understanding how a type of white blood cell called the eosinophil may help the body to fight bacterial infections in the digestive tract, according to ...

New clues about mitochondrial 'growth spurts'

Mar 02, 2009

Mitochondria are restless, continually merging and splitting. But contrary to conventional wisdom, the size of these organelles depends on more than fusion and fission, as Berman et al. show. Mitochondrial ...

A new brake on cellular energy production discovered

Jul 27, 2007

A condition that has to be met for the body to be able to keep warm, move and even survive is that the mitochondria - the cells' power stations - release the right amounts of energy. Scientists at Karolinska Institutet have ...

Recommended for you

Breakthrough in understanding of important blood protein

35 minutes ago

The human body contains a unique protein that has the unusual property of destroying itself after a few hours of existence - it must therefore be continually recreated and is no stable protein. The protein, ...

Key to aging immune system is discovered

1 hour ago

There's a good reason people over 60 are not donor candidates for bone marrow transplantation. The immune system ages and weakens with time, making the elderly prone to life-threatening infection and other ...

Putting a number on pain

1 hour ago

"How much pain are you in?" It's a harder question than many people think. Tools for assessing patients' pain—be they children or adults—rely on perception: a subjective measure that eludes quantification ...

New infections cause dormant viruses to reactivate

1 hour ago

The famous slogan is "A diamond is forever," but that phrase might be better suited to herpes: Unlike most viruses, which succumb to the immune system's attack, herpes remains in the body forever, lying in wait, sometimes ...

User comments : 0