Associate Professor University of Louisville Louisville, Kentucky, United States
Brian Clem (University of Louisville)| James Bradley (University of Louisville)| Daniel Wilkey (University of Louisville)| Michael Merchant (University of Louisville)| John Trent (University of Louisville)| Rumeysa Biyik-Sit (University of Louisville)
Altered cellular metabolism is evident in a majority of human cancers and allows for anabolic precursors that are necessary to sustain rapid and untethered proliferation. Increased serine synthesis is mediated by elevated enzyme expression including phosphoserine aminotransferase 1 (PSAT1), whose transcript levels are negatively associated with patient outcomes in NSCLC. While serine production for protein synthesis and one carbon metabolism is important for tumor cell survival and proliferation, the requirement for PSAT1 in lung tumor progression may not be completely understood. To investigate additional activities of PSAT1 that may be contributing to lung tumorigenesis, we sought to identify potential PSAT1 interacting proteins. Mass spectrometry analysis identified PKM2, which was verified by co-immunoprecipitation. This association appeared to be selective for PKM2 as PSAT1 failed to interact with recombinant PKM1. While having no effect on cellular pyruvate kinase activity, we found that PSAT1 silencing blocked EGFR-activated nuclear translocation of PKM2. We also observed EGFR-mediated nuclear localization of PSAT1, but their compartmentalization is not directly due to this association as interaction-mutant PKM2 was still able to localize to the nucleus. Functionally, PSAT1 suppression abrogated cell motility/migration in EGFR-mutant PC9 and EGF-stimulated A549 cells. To investigate a role of nuclear PKM2, we introduced PKM2 variants tagged with a nuclear localization signal (NLS) into PSAT1 silenced PC9 cells. We found that re-expression of NLS-PKM2 acetyl-mimetic mutant, but not wild-type, partially restores the cell migration in PSAT1 depleted cells. Taken together, our findings suggest that PSAT1 contributes to mutant EGFR-driven lung cancer cell migration in part through promoting nuclear PKM2 translocation.