"The protein Rictor is modular and multifunctional," said Wei. "Its function depends on its partners." This observation suggests that some proteins may act like a central machine that can work with a variety of attachments, the same way a construction vehicle can change its function depending on whether it's wielding a bulldozer or a crane. "With further study," he adds, "we may find more proteins [like Rictor] that have multiple functions. When a cell makes a protein this big, isn't it a waste of energy to have only one function?"
Wei's team further observed that once SGK1 begins to accumulate, it turns right around and interrupts the Rictor-Cullin1 complex, stifling it's garbage collection activities. "It looks like a positive feedback loop that serves to increase SGK1," says Wei.
"The novelty and significance of this work lies in the discovery of a role for Rictor in destroying SGK1, a key regulator of cell growth and cell death that is frequently associated with human cancers," said Marion Zatz, PhD, who manages cell cycle grants at the National Institutes of Health (NIH). "The finding suggests that faulty regulation of Rictor may play a part in some forms of cancer, and could offer us a new target for treating the disease."
While the exact role of SGK1 in tumor growth isn't yet clear, Wei speculates that SGK1 may play a role in cancer by hijacking a cell's metabolism, just as its close cousin AKT does. "This mechanism we discovered may be part of what drives overexpression of SGK1," he adds.
|Contact: Bonnie Prescott|
Beth Israel Deaconess Medical Center