ADAM17-induced shedding of glypican-1 as a mechanism of impaired endothelial shear stress mechanotransduction.

Endothelial dysfunction occurs early in the pathogenesis of type 2 diabetes (T2D)-associated cardiovascular disease. Previous work has revealed that endothelial glycocalyx mechanosensing structures are degraded in T2D, likely contributing to impaired shear stress mechanotransduction and consequent blunted vasodilation. Evidence from proteomic analysis suggests that glypican-1, a well-known mechanosensor, is a substrate of the proinflammatory enzyme ADAM17. A critical step in ADAM17 activation is externalization of phosphatidylserine (PS) to the outer leaflet of the plasmalemma, which can be enacted by the Ca2+-activated phospholipid scramblase anoctamin-6 (ANO6). However, whether ANO6-mediated activation of ADAM17 leads to glypican-1 shedding in endothelial cells remains unknown. Also, unknown are the mechanisms by which this pathway becomes overactive in T2D. We recently reported that the activity of neuraminidase, a soluble enzyme that cleaves sialic acid, is elevated in the plasma of individuals with T2D and that this occurs in concert with increased ADAM17 activity. Here, in an extended cohort of males and females with T2D, we report that this association is also coupled with reduced flow-mediated dilation (FMD). Furthermore, we report that subjecting endothelial cells to neuraminidase increases intracellular Ca2+, which provokes ANO6-mediated PS externalization, leading to ADAM17-dependent reductions of glypican-1. In isolated arteries, intraluminal exposure to neuraminidase impairs FMD, which can be prevented by ANO6 or ADAM17 inhibition. Lastly, isolated arteries from endothelial cell-specific ADAM17 knockout mice fed a Western diet exhibit greater FMD than genetic controls. Collectively, this work identifies the neuraminidase-ANO6-ADAM17 axis as a potential novel mechanism underlying impaired endothelial shear stress mechanotransduction in T2D.NEW & NOTEWORTHY We provide evidence that neuraminidase, which is elevated in plasma from males and females with type 2 diabetes (T2D), is involved in the activation of endothelial ADAM17 and shedding of the mechanosensor glypican-1. We also provide evidence that neuraminidase-induced ADAM17 activation and consequent glypican-1 shedding are mediated by ANO6 scramblase externalization of phosphatidylserine. Together, this work suggests the neuraminidase-ANO6-ADAM17 axis may be a mechanism underlying impaired endothelial shear stress mechanotransduction in T2D.