Endothelial pyruvate kinase M2 maintains vascular integrity
Boa Kim, … , Kristina Li, Zolt Arany
Boa Kim, … , Kristina Li, Zolt Arany
Published September 17, 2018
Citation Information: J Clin Invest. 2018;128(10):4543-4556. https://doi.org/10.1172/JCI120912.
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Research Article Metabolism Vascular biology

Endothelial pyruvate kinase M2 maintains vascular integrity

Abstract

The M2 isoform of pyruvate kinase (PKM2) is highly expressed in most cancer cells, and has been studied extensively as a driver of oncogenic metabolism. In contrast, the role of PKM2 in nontransformed cells is little studied, and nearly nothing is known of its role, if any, in quiescent cells. We show here that endothelial cells express PKM2 almost exclusively over PKM1. In proliferating endothelial cells, PKM2 is required to suppress p53 and maintain cell cycle progression. In sharp contrast, PKM2 has a strikingly different role in quiescent endothelial cells, where inhibition of PKM2 leads to degeneration of tight junctions and barrier function. Mechanistically, PKM2 regulates barrier function independently of its canonical activity as a pyruvate kinase. Instead, PKM2 suppresses NF-kB and its downstream target, the vascular permeability factor angiopoietin 2. As a consequence, loss of endothelial cell PKM2 in vivo predisposes mice to VEGF-induced vascular leak, and to severe bacteremia and death in response to sepsis. Together, these data demonstrate new roles of PKM2 in quiescent cells, and highlight the need for caution in developing cancer therapies that target PKM2.

Authors

Boa Kim, Cholsoon Jang, Harita Dharaneeswaran, Jian Li, Mohit Bhide, Steven Yang, Kristina Li, Zolt Arany

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Figure 1

ECs predominantly express PKM2 over PKM1.

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ECs predominantly express PKM2 over PKM1. (A) Schematic illustration of ...
(A) Schematic illustration of alternative splicing of PKM1 and PKM2. The mutually exclusive exons for PKM1 (exon 9) and PKM2 (exon 10) are indicated in blue and pink, respectively. (B) Western blot analysis of PKM1 and PKM2 in various tissues from mouse and 2 different human-derived primary ECs. CD31+ ECs from mouse were directly lysed in RIPA buffer immediately after isolation, without cell culture. SKM, skeletal muscle; SOL, soleus; Quad, quadriceps; HUVEC, human umbilical vein endothelial cells; ECFC, endothelial colony forming cells. (C) qPCR analysis of PKM1 and PKM2 mRNA expression in subconfluent HUVECs (n = 3). (D) Staining of endothelial PKM2 in a scratch assay setting. HUVECs were cultured at full confluency for 3 days and scratch was made. PKM2 (green) was costained with phalloidin (red) and DAPI (blue) after 24 hours. Scale bar, 100 μm. (E) ECs lining both large vessels and the microvasculature in mouse heart and skeletal muscle express PKM2, in sharp contrast to adjacent cardiac and skeletal muscle cells that exclusively express PKM1 (shown in B). Cross-section of mouse heart was immuno-stained with PKM2 (red), IsoB4 (green), and DAPI (blue). v, lumen of a large vessel. Whole-mount staining of ECs lining microvasculature in the skeletal muscle of mouse is shown on bottom. PKM2 (red), CD31 (green). Scale bar, 50 μm. All data are mean ± SD. **P < 0.01, by 2-tailed Student’s t test.