At least your cells know how to limit their stress.
Scientists at Northwestern University have learned how stress molecules in cells turn off their own production so they don't keep cells in a chronically stressed state even if adverse conditions persist. The finding, reported in the July issue of Genes & Development, identifies a new off-switch molecule in the control of the stress response and may have implications in the cell death that occurs in aging and in diseases from infections to heart disease and stroke.
Cells produce heat shock proteins, or HSPs, in response to stress caused by heat, poisons or signals from nerves or hormones. These heat shock proteins are sometimes called molecular chaperones, because their role is to protect and usher other protein molecules around in the cell. Even under non-stressed conditions, lower levels of chaperones are essential to protect newly made proteins from clumping together or being broken down before they can fold up into their final shape or be threaded through internal membranes to the cellular compartment where they are needed.
"Chaperones play an essential, normal role in regulating protein equilibrium, the balance between synthesis and degradation," said Richard I. Morimoto, John Evans Professor of Biology, who led the study. "If you expose the cell to stress -- whether heat stress, or oxygen stress as occurs in infection, immunity, myocardial stress or neurodegenerative disease -- the cell responds by making more chaperones to protect its vital proteins," he said.
But the level of chaperones is critical, and too much is also harmful to the cell. Even as they protect other proteins, chaperones straitjacket them and prevent them from carrying out their vital functions.
"If you make too much of the chaperones, the cell is never going to get back to
its normal state," said Morimoto, who is also chair of biochemistry, molecular
biology and cell biology and director of the Rice Institute for Biomedic
Contact: Bill Burton