McKelvey School of Engineering

WashU engineers manage a first: measuring pH in cell condensates

Researchers were able to measure pH in a type of condensate called the nucleolus, the site of ribosome production. They report that the distinct protein compositions of nucleoli give them an acidic character. (Image: Matthew King)

Scientists trying to understand the physical and chemical properties that govern biomolecular condensates now have a crucial way to measure pH and other emergent properties of these enigmatic, albeit important cellular compartments.

Condensates are communities of proteins and nucleic acids. They lack a membrane and come together and fall apart as needed. The nucleolus is a prominent condensate in cells. It serves vital roles in cellular physiology and is the site of ribosome production.

Ribosomes are the multi-protein and RNA assemblies where the genetic code is translated to synthesize proteins. Impairment of ribosome production and other nucleolar dysfunctions lie at the heart of cancers, neurodegeneration and developmental disorders.

In a first for the condensate field, researchers from the lab of Rohit Pappu, PhD, the Gene K. Beare Distinguished Professor of biomedical engineering, and colleagues in the Center for Biomolecular Condensates in the McKelvey School of Engineering at Washington University in St. Louis, figured out how nucleolar substructures are assembled. This organization gives rise to unique pH profiles within nucleoli, which they measured and compared with the pH of nearby non-nucleolar condensates including nuclear speckles and Cajal bodies.

In the study, published online in Cell, the authors report that the distinct protein compositions of nucleoli give them an acidic character, whereas nuclear speckles have the same pH as the nucleus, and Cajal bodies are more basic.

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