Katharine White

Cellular pHi dynamics: regulating proteins, pathways, and cell behaviors

Transient increases in intracellular pH (pHi) are necessary for normal cell processes of cell-cycle progression, migration, and differentiation while dysregulated pHi dynamics are linked to diseases such as neurodegeneration and cancer. While the effects of pHi on global cell behaviors is well established, the proteins and molecular mechanisms that drive these pH-sensitive responses are largely unknown. Furthermore, a lack of tools to directly, specifically, and spatiotemporally manipulate pHi has restricted experiments probing how pH dynamics alter individual cell behaviors.

A long-term goal of our research is to understand how protonation events are integrated across biological scales to induce coordinated changes from proteins, to macromolecular assemblies, to cell behavior and more complex tissue-level effects.

To address this goal, we are performing interdisciplinary research across experimental scales. At the molecular scale, we are identifying pH-sensing mechanisms utilized by both wildtype and mutant proteins. We will apply this knowledge to generate essential design principles of pH sensing proteins and engineer minimal pH-sensitive protein modules. At the cellular scale, we are developing new optogenetic tools to spatiotemporally manipulate pHi in living cells. We use light microscopy to develop and test these tools and apply them to probe how changing pHi alters both individual and population-level cell behaviors. At the tissue scale, we are interested in how pH changes are communicated across a spheroid (which mimics 3D tissue architectures). This work mimics effects of early cancer development and will answer an ongoing question in the field: whether increased pHi in an individual cell can produce global cancer-like effects.

We use a variety of techniques to answer these questions, supporting classic biophysical and biochemical assays with quantitative light microscopy approaches.

Publications

1. "Cancer-associated arginine-to-histidine mutations confer a gain in pH sensing to mutant proteins" White, K.A; Garrido, R.D.; Szpiech, Z.A.; Strauli, N.B.; Hernandez, R.D.; Jacobson M.P.; Barber, D.L.Sci. Signaling 2017, 10, 495.
2. "Cancer cell behaviors mediated by dysregulated pH dynamics at a glance" White, K.A; Grillo-Hill, B.K.; Barber, D.L.J. Cell Sci. 2017, 130, 663-669.
3. "A histidine cluster in the cytoplasmic domain of the Na-H exchanger NHE1 confers pH-sensitive PIP2 binding and regulates transporter activity" Webb, B.A.; White, K.A; Grillo-Hill, B.K.; Schonichen, A.; Choi, C.C.; Barber, D.L. J. Biol. Chem. 2016, 291, 24096-104.
4. "Directed evolution of a probe ligase with activity in the secretory pathway and application to imaging intercellular protein-protein interactions" White, K.A; Zegelbone, P.M. Biochemistry 2013, 52, 3728-3739.