The team developed a high-throughput imaging platform to assess the influence of nearly 3,500 mutations on protein location. They found that about one in six disease-causing mutations led to proteins ending up in the wrong location in the cell.

Technological advances in genetic sequencing have allowed researchers to identify thousands of disease-causing protein mutations. We are now able to identify these mutations in patients in the clinic, but we have no idea what their consequences are for cellular processes. This study was intended to help close this knowledge gap.”

Jessica Lacoste, co-senior author of the study and a postdoctoral fellow at the Donnelly Center for Cellular and Biomolecular Research at U of T

The study was recently published in the journal Cell.

There are several ways genetic mutations it can affect the proteins produced in the cell. For example, they can reduce their overall stability by affecting their ability to fold, alter their interactions with other proteins, or disrupt their movement in different regions of the cell. While the first two effects have been fairly well studied, much less is known about the third. Improving our understanding of the impact of mutations on protein localization is critical to elucidating the critical role of this defect in a wide range of human diseases.

The research team used a powerful microscope -; as well as computational analysis to fill in the gaps in their visual analysis -; to compare the cellular journeys made by the mutant proteins with those made by the regular proteins. Through these methods, they learned that mislocalization occurs much more frequently than previously thought.

The researchers expected the proteins to be in the wrong locations due to disruptions in their interactions with other proteins or traffic signals that would normally guide them to the correct location. They were surprised to learn that the main drivers of misplaced proteins were actually a breakdown in protein stability and loss of their ability to integrate into membranes.

“We created the first large-scale map to visualize the impact of mutations on protein localization inside the cell,” said Mikko Taipale, study co-principal investigator and professor of molecular genetics at the Donnelly and Temerty Center at the University of T. Faculty of Medicine. “No one else has studied the impact of pathogenic missense mutations on a scale like this, where we tracked the movement of proteins to different organs. The patterns of mislocalization we observed help explain the severity of disease caused by certain mutations and improve us. understanding mutations that have been less studied.”

While protein mislocalization is not as well understood as general loss of protein stability or altered interactions with other proteins, it occurs almost as often. The mutation most commonly linked to cystic fibrosis causes the affected protein to end up in the cell’s endoplasmic reticulum, where it remains instead of moving to its correct location on the cell surface. Drug therapies that promote proper trafficking of the mutant protein are currently being used in the clinic to address this problem and improve patients’ symptoms.

“We have made our protein mislocalization database available as a comprehensive resource that can be used by other researchers to expand our collective knowledge of the effects of genetic variation on human disease,” said Anne Carpenter, co-principal investigator of study and principal. director of the Imaging Platform at the Broad Institute. “A particularly useful application of this data would be to identify compounds that could help mutant proteins localize correctly to treat rare diseases.”

This research was supported by the Canadian Institutes of Health Research, the Texas Institute for Cancer Prevention and Research, the National Institutes of Health, the Ontario Ministry of Research and Innovation, the Susan G. Komen Foundation, and the University of Toronto’s Connaught Fund.