New Regulatory Mechanism Discovered In Cell System For Eliminating Unneeded Proteins

Work led by St. Jude Children's Research Hospital scientists offers clues into molecular malfunction at the heart of a rare blood vessel disorder, revealing an important new regulator of cellular proteins

MEMPHIS, Tenn., Aug. 10, 2012 /PRNewswire-USNewswire/ -- A faulty gene linked to a rare blood vessel disorder has led investigators to discover a mechanism involved in determining the fate of possibly thousands of proteins working inside cells.

St. Jude Children's Research Hospital scientists directed the study, which provides insight into one of the body's most important regulatory systems, the ubiquitin system. Cells use it to get rid of unneeded proteins. Problems in this system have been tied to cancers, infections and other diseases. The work appears in today's print edition of the journal Molecular Cell.

Researchers demonstrated how a protein named Glomulin binds to a key component of the regulatory system. Investigators showed not only where Glomulin binds but also how binding shuts down a biochemical cascade that tags unnecessary proteins for dismantling.

The findings highlight a potential new approach for future studies aimed at developing treatments for glomuvenous malformations, which are associated with mutations in the gene for making the Glomulin protein. The malformations, which are often present at birth, result in veins that cause discolored raised skin lumps that are sometimes painful and disfiguring.

"The findings suggest it might someday be possible to treat disorders resulting from defects in proteins that shut off the ubiquitin system by finding an alternative mechanism for turning the pathway off. The way Glomulin works represents a new way of controlling one of the most important regulatory systems at work in cells. We believe Glomulin may represent the tip of the iceberg. There could be many proteins that work in this fashion," said Brenda Schulman, Ph.D., a member of the St. Jude Department of Structural Biology and a Howard Hughes Medical Institute investigator. She is the study's senior and corresponding author.

Cells rely on this ubiquitin system to keep proteins in balance. As part of the ubiquitination process, a small protein is passed from one enzyme to the next like a baton in a relay race until it reaches a protein complex known as the cullin RING ligase. There, the small protein is transferred to a waiting target protein, marking it for destruction.

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