322 - Detection of Pyruvate Kinase Isoform M2 (PKM2) in Arterial Wall Cells, Intact Arteries and Human Atherosclerotic Lesions

Abstract

Background Pyruvate kinase is the last, and rate-limiting enzyme in glycolysis. It exists in multiple isoforms adapted to tissue requirements. The M2 isoform is strongly linked with the Warburg effect and tumours, with switching of glucose metabolism (from Krebs cycle to pentose phosphate pathway) linked to the need for reducing equivalents to maintain redox homeostasis and synthetic intermediates for cell division. As endothelial cells and smooth muscle cells also undergo metabolic switching from quiescent to proliferative phenotypes during angiogenesis and hyperplasia respectively, we hypothesized that these cells would also express the PKM2 isoform. Methods PKM activity was determined by enzyme assay with or without allosteric regulators and inhibitors. Protein isoforms were probed using specific antibodies. LC-MS peptide mass mapping was used to examine the presence of isoform specific peptides. Results PKM2 activity, protein (Western blotting) and peptides (LC-MS) were detected in primary human coronary arterial endothelial and smooth muscle cells, in normal mammary artery samples and in carotid and aortic atherosclerotic lesions. Data-mining of a normal mammary artery tissue proteome dataset showed no significant correlations of specific M1, M2 or common peptides with clinical parameters (age, smoking, systolic blood pressure, diastolic blood pressure, BMI, HbA1c, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, total cholesterol, plasma creatinine and C-reactive protein). Conclusions These data are consistent with the presence of PMK2 in human endothelial and smooth muscle cells and normal and diseased arterial tissue, and a capacity of vascular cells to regulate glucose metabolism in an allosteric manner. This may be linked to metabolic pathway switching during conversion from quiescent to synthetic / proliferative phenotypes.