Dysregulated intracellular pH (pHi) dynamics is increasingly recognized as a feature of disparate diseases. Compared with normal cells, most cancers have a constitutively higher pHi and neurodegenerative disorders are associated with a lower pHi. However, how dysregulated pHi dynamics modulates the response to disease associated mutations, many which encode a change in protein charge, has received limited attention. Focusing on somatic mutations in cancer, we determined that nearly 40% encode a change in protein charge, with Arg&gt;His and Glu&gt;Lys being predominant. We found that Arg&gt;His mutations can confer a gain in pH sensing functions not seen with the wild-type proteins and His&gt;Arg mutations can confer loss of pH sensing identified in wild-type proteins. We confirmed a gain in pH sensing for p53-R273H, EGFR-R776H, and Smad4-R361H. For p53-R273H, one of the most recurring p53 mutations, the higher pHi of cancer cells decreases binding of the mutant but not wild-type protein to DNA, which attenuates tumor suppressor activity and the DNA damage response. A higher pHi also increases activity of EGFR-R776H, a recurring mutation in lung cancer, but not wild-type EGFR, which is mediated by pH-regulated conformational changes in the aC-helix of the mutant kinase domain and results in increased cell proliferation and transformation. Smad4 binds to Smad3 in part through a Smad4-Arg361 and Smad3-Asp408 salt bridge to mediate transcriptional responses to transforming growth factor b. This binding is pH insensitive with wild-type Smad4 but pH sensitive with Smad-R361H, which is recurring in pancreatic cancers, with Smad3 binding retained at <u>&lt; </u>7.2 but attenuated at pH &gt; 7.5. In contrast, the cancer-associated b-catenin-H36R mutation confers a loss of pH sensing that for wild-type b-catenin has a pH-regulated binding to the E3 ligase b-TrCP1 mediated by the protonation state of His36. Hence, we identified molecular mechanisms whereby pH dynamics can determine the function of tumor suppressor and oncogenic charge-changing mutations associated with cancers. In addition to cancer, many diseases are associated with charge-changing mutations, which raises questions on the role of pHi dynamics in mutation-driven pathologies and provides new insights for therapeutic targeting.

Intracellular pH dynamics and charge-changing mutations in disease

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.