Abstract 16772: Discovery of a Novel Approach for Modulating Angiogenesis: The Interaction Between Heat Shock Protein 27 and ATP5A1 Promotes Endothelial Cell Dynamics

Introduction: ATP5A1 is the alpha subunit of the soluble F1 catalytic core of mitochondrial ATP synthase that catalyzes ATP synthesis. Previous studies identified ATP synthase as the receptor for the anti-angiogenic factor, angiostatin. We demonstrated that Heat Shock Protein 27 (HSP27) functions in the extracellular space to accelerate re-endothelialization (FASEB 2014) and more recently using mass spectrometry identified ATP5A1 as a potential cell membrane client protein of HSP27. Hypothesis: HSP27 interacts with ATP5A1 to promote endothelial dynamics. Methods / Results: (1) The binding of HSP27 to ATP5A1 was quantified using an ELISA by coating plates with an anti-ATP5A1 antibody. While a negative control truncated C-terminus form of HSP27 did not bind ATP5A1, full length HSP27 showed an abundant binding pattern to HSP27 that was further enhanced by the presence of auto-antibodies to HSP27. (2) As detected by immunofluorescence imaging and use of a fluorescent activated cell sorter, ATP5A1 expression was up-regulated in endothelial cells that over-express HSP27. (3) ATP production in endothelial cells was increased after exposure to HSP27 (p (4) Endothelial cell migration in vitro was increased with the addition of HSP27. Indeed, HSP27 in combination with anti-HSP27 auto-antibodies potentiated the interaction with ATP5A1. Conclusions: The interaction of HSP27 with cell membrane localized ATP5A1 appears to be a key mechanism of enhancing endothelial cell dynamics. Interestingly, the presence of auto-antibodies to HSP27 potentiates this effect and is explained in separately described data regarding anti-HSP27 immune phenomena in cell signaling. These data provide for the first time impetus for the development of angiogenesis modulating strategies that either promote or antagonize the interaction between HSP27 and ATP5A1 in order to enhance or suppress angiogenesis, respectively.