Structural and mechanistic insights into cancer promoting activities of pyruvate kinase muscle isoform-2

Pyruvate Kinase catalyzes the conversion of phosphoenolpyruvate (PEP) to pyruvate with the production of ATP in the final reaction of glycolysis. The M2 isoform of the PK gene is significantly upregulated in cancer tissues and is a critical regulator of Warburg effect. The tetrameric form of PKM2 has higher kinase activity than the dimer, which supports the growth of tumor by nuclear translocation. The study aims to determine how different conditions such as an alkaline pH (prevalent in cancer cells), and a hyperthermic environment (shown to kill tumor cells) can aid or alleviate cancer progression, by acting via PKM2 which is a central protein in cancer. An alkaline pH of 8.0 was shown to alter the oligomerization state of the protein, promoting the formation of the nuclear-translocating and cancer-promoting dimeric form. The kinase activity was also hampered supporting the higher oncoprotein function. On the other hand, a hyperthermic environment of 42°C was shown to induce changes in the overall structure and stability of PKM2 at secondary and tertiary level, ascertained via Circular Dichroism and Thermal Fluorimetry. As the protein was unable to retain its structure at the slightly higher temperature, the oncoprotein activity of the protein was also obliterated, which may hint towards a possible pathway through which the therapeutic hyperthermia works on cancer cells. Deeper analysis of these mechanisms was performed by testing these conditions with cancer patient-derived mutants of PKM2. The mutants were also crystallized and diffracted at <3Å resolution, which will be solved to gain in-depth structural insights on this protein. This study will unravel novel mechanisms and structural details of PKM2 which will aid in better understanding of the role of PKM2 in the manifestation of disease.