[Homestead] Tooth loss due to P Gingivalis

tvoivozhd tvoivozd at infionline.net
Wed Feb 9 08:49:18 EST 2005


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/Source:/ 	*University Of Florida Health Science Center* 	
/Date:/ 	2005-02-09
/URL:/ 	http://www.sciencedaily.com/releases/2005/02/050205123823.htm

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    UF Researchers Map Bacterial Proteins That Cause Tooth Loss

The human mouth teems with millions of enamel-eroding, gum-inflaming 
microbes.

One of these, Porphyromonas gingivalis, is a bacterial homesteader that 
stakes a claim deep within the spaces between teeth and gums. It’s also 
the leading cause of tooth loss — secreting proteins that destroy the 
soft tissues and bone that support teeth to cause periodontal disease.

Now scientists have identified the thousands of proteins the bacterium 
produces, shedding light on how it interacts with healthy cells in order 
to thrive, according to dental researchers from the University of 
Florida and the University of Washington. They describe their findings 
in the current issue of the journal Proteomics.

“Determining which proteins are expressed in greater levels in the mouth 
has allowed us to gain clues as to how P. gingivalis might be causing 
disease, and what we might be able to do with drugs or vaccines to 
prevent it,” said Richard Lamont, Ph.D., a professor of oral biology at 
UF’s College of Dentistry and study investigator.

The National Institute of Dental and Craniofacial Research estimates 80 
percent of adult Americans have some form of periodontal disease, their 
symptoms ranging from mild gum irritation to complete tooth loss.

People with periodontal disease also are at increased risk of stroke and 
heart attack, and the disease makes it difficult to control blood sugar 
levels in people with diabetes. If that’s not bad enough, pregnant women 
with periodontal disease are seven times more likely to deliver 
low-birth-weight, preterm babies. Proteins are important to study 
because they are the foundation of the cellular structure of every 
living organism, Lamont said. They carry on the day-to-day biology of 
life, going about their business as enzymes and antibodies. They can 
also cause disease.

“The genes themselves are only important in that they encode the 
proteins,” Lamont said. “It’s the proteins that are most responsible for 
disease, and in most cases it’s proteins that are vaccine and drug targets.”

The scientists have been trying to understand how P. gingivalis 
interacts with healthy oral tissues to cause such devastation. In this 
study, they used cutting-edge molecular research techniques to map all 
the proteins — known as the proteome — produced by P. gingivalis. 
Ultimately, the researchers were able to fill hundreds of gaps in the 
organism’s sequence of roughly 2,000 proteins.

“The approach used in this study is very exciting,” said Hansel 
Fletcher, Ph.D., an associate professor of microbiology and molecular 
genetics at Loma Linda University in Loma Linda, Calif. “For the first 
time, we are able to see that the more than 200 so-called ‘hypothetical’ 
proteins in P. gingivalis are expressed and have specific functions.”

Until now, scientists had identified less than 2 percent of the 
pathogen’s proteins and had to guess at what other proteins might be 
present in the proteome based on similarities to other known proteins, 
said Fletcher.

“This study has done two things to advance that,” Lamont said. “We’ve 
identified the complete protein complement of the organism, and we’ve 
looked at how those proteins are expressed when the organism is in an 
environment that closely mimics an oral situation.”

To do this, Lamont and his colleagues compared the proteins secreted by 
P. gingivalis when grown in a medium containing human gum cell proteins 
with the proteins produced by the bacteria when grown in a neutral 
medium. Bacterial proteins from the two conditions were separated using 
a new technique called Multidimensional Protein Identification 
Technology, or MudPIT.

Once separated, mass spectrometry was used to measure each protein’s 
mass and charge, identifiers as unique to proteins as the whorls of 
fingerprints are to people.

The spectrometry measurements were fed into a computer database to 
create a computational model of the P. gingivalis proteome, resulting in 
a surprising find.

“Some of the proteins we previously thought were important when they 
were expressed in the lab proved not to be when the organism is in an 
environment that mimics the oral cavity,” Lamont said.

To put it simply, the behavior, or protein expression, of the organism 
when it’s at work in the human mouth is very different from its behavior 
when it’s vacationing in a Petri dish.

“An organism growing in a lab isn’t causing disease,” Lamont said. “It’s 
an organism that’s in your gums, your lungs, your heart valves, your 
arteries causing disease.”

The next step will be to expose P. gingivalis to other oral pathogens to 
determine what interactions may exist that contribute to infection, he said.

“This study is important in that we now have an understanding of the 
protein expression on a global scale for this pathogen,” Lamont said. 
“Now we need to see how it adapts to various situations present in the 
mouth to cause disease.”

*Editor's Note:* The original news release can be found here 
<http://news.health.ufl.edu/stories/2005/Feb/Gingivalis.shtml>.

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/This story has been adapted from a news release issued by University Of 
Florida Health Science Center./





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