Dysregulated pH is a hallmark of nearly all cancers regardless of tissue origin or genetic background. In normal cells, extracellular pH (pHe) is higher than intracellular pH (pHi) but in cancer cells this pH gradient is reversed. While the constitutive increase in pHi is small, it produces substantial changes in cell function. For example, the the increased pHi of cancer cells promotes cell proliferation and invasion while inhibiting apoptosis and altering cell metabolism. Here, we propose to investigate somatic mutations in cancer that may be conferring an increased fitness for the dysregulated pH of cancer. While somatic mutations in cancer are random, the increased pHi of cancers could provide a selective pressure for mutations that confer an adaptive advantage. Our hypothesis is that this selective pressure causes the conservation of histidine mutations in cancer that confer a gain in pH sensitivity. To investigate this hypothesis, in Aim 1 we will determine whether commonly occurring Arg>His mutations in candidate proteins confer a gain in pH-dependent function and what the mechanism of pH sensing might be. For each candidate we will test predictions that mutant but not wild- type proteins have pH-dependent functions by using biochemical assays in vitro and in cells. We also will test mechanisms of pH sensing of mutants by using molecular dynamics simulations and computational pKa predictions.
In Aim 2 we will use database analyses to identify additional candidates with recurring histidine mutations, determine their frequency relative to codon bias frequency, and generate interaction networks to predict how these mutations might be conferring a functional adaptive advantage to cancer cells. These objectives will be achieved by using a database of amino acid mutations generated for the sponsor's laboratory from the Catalogue Of Somatic Mutations In Cancer (COSMIC) and established bioinformatics programs. To our knowledge this is the first examination of the adaptive retention and pH-dependent function of somatic mutations involving histidines in cancer. Our findings will generate new insights into how somatic mutations might be linked to the dysregulated pH in cancer. The results of this work might also reveal broad design principles of pH sensors that could inform the development of cancer therapeutics targeting pH-dependent pathways, regulatory mechanisms, or driver mutations.

Public Health Relevance

Although cancer is a diverse set of diseases, one of the hallmarks of nearly all cancers is constitutively increased intracellular pH. We propose investigating conserved histidine mutations in cancer that might be conferring an adaptive advantage to the increased intracellular pH of cancers. The results of this work might reveal new pH-dependent pathways and also contribute to new developing new therapeutic approaches to limit cancer progression.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32CA177085-01
Application #
8526795
Study Section
Special Emphasis Panel (ZRG1-F09-L (20))
Program Officer
Jakowlew, Sonia B
Project Start
2013-08-01
Project End
2016-07-31
Budget Start
2013-08-01
Budget End
2014-07-31
Support Year
1
Fiscal Year
2013
Total Cost
$47,114
Indirect Cost
Name
University of California San Francisco
Department
Anatomy/Cell Biology
Type
Schools of Dentistry
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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White, Katharine A; Grillo-Hill, Bree K; Barber, Diane L (2017) Cancer cell behaviors mediated by dysregulated pH dynamics at a glance. J Cell Sci 130:663-669
Vercoulen, Yvonne; Kondo, Yasushi; Iwig, Jeffrey S et al. (2017) A Histidine pH sensor regulates activation of the Ras-specific guanine nucleotide exchange factor RasGRP1. Elife 6:
Szpiech, Zachary A; Strauli, Nicolas B; White, Katharine A et al. (2017) Prominent features of the amino acid mutation landscape in cancer. PLoS One 12:e0183273
White, Katharine A; Ruiz, Diego Garrido; Szpiech, Zachary A et al. (2017) Cancer-associated arginine-to-histidine mutations confer a gain in pH sensing to mutant proteins. Sci Signal 10:
Webb, Bradley A; White, Katharine A; Grillo-Hill, Bree K et al. (2016) A Histidine Cluster in the Cytoplasmic Domain of the Na-H Exchanger NHE1 Confers pH-sensitive Phospholipid Binding and Regulates Transporter Activity. J Biol Chem 291:24096-24104