New research maps cell reactions to and defence against arsenic and cadmium
New research at the University of Gothenburg shows that arsenic and cadmium, which are poisonous to humans, contribute to the clumping together of proteins in cells and the forming of aggregates, which are linked to diseases like Alzheimer's and Parkinson's. “But we have also succeeded in identifying a defence mechanism that prevents arsenic from being absorbed by cells,” said Therese Jacobson, doctoral student at the Department of Chemistry and Molecular Biology.
Arsenic and cadmium are two toxic elements for humans and they occur naturally in bedrock. Arsenic can poison groundwater, resulting in local populations in some places in the world being continually exposed.
“Some crops, particularly rice, absorb arsenic very effectively because the proteins in the roots cannot distinguish between arsenic and the essential element phosphorus,” says Therese Jacobson, doctoral student at the Department of Chemistry and Molecular Biology. “Cadmium, in turn, is spread mainly by fertilizers and cigarette smoke.”
Her doctoral thesis deals with research trying to understand how cells respond to and defend against arsenic and cadmium. Therese and her colleagues have succeeded in identifying a defence mechanism in yeast cells. The mechanism involves the secretion of a type of molecule, glutathione, which consists of three amino acids and which binds arsenic outside the cells.
“By binding the arsenic, it is prevented from being absorbed into the cells,” she says.
Contribute to proteins clumping together
Therese has concluded in her research that arsenic and cadmium contribute to proteins clumping together and forming aggregates. This aggregation, in turn, is negative for the cells — several neurodegenerative diseases, like Alzheimer's and Parkinson's, are linked to proteins forming aggregates. Therese’s research shows that arsenic and cadmium contribute to protein aggregation in different ways.
“Arsenic prevents chaperone proteins from performing their important function,” she says. “Chaperones help newly formed proteins to take their correct three-dimensional shape. If these newly-formed proteins do not take their proper shape, this increases the likelihood that they will clump together with other proteins to form aggregates.”
Cadmium, in turn, affects zinc-binding proteins. Zinc ions are important for certain proteins to take their proper shape, and this research shows that cadmium appears to replace the zinc in these proteins, thus leading to aggregation.
Therese Jacobson, the Department of Chemistry and Molecular Biology
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