The endothelial cell receptor GRP78 is required for mucormycosis pathogenesis in diabetic mice
Mingfu Liu, … , Scott G. Filler, Ashraf S. Ibrahim
Mingfu Liu, … , Scott G. Filler, Ashraf S. Ibrahim
Published May 17, 2010
Citation Information: J Clin Invest. 2010;120(6):1914-1924. https://doi.org/10.1172/JCI42164.
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Research Article Infectious disease

The endothelial cell receptor GRP78 is required for mucormycosis pathogenesis in diabetic mice

Abstract

Mucormycosis is a fungal infection of the sinuses, brain, or lungs that causes a mortality rate of at least 50% despite first-line therapy. Because angioinvasion is a hallmark of mucormycosis infections, we sought to define the endothelial cell receptor(s) for fungi of the order Mucorales (the fungi that cause mucormycosis). Furthermore, since patients with elevated available serum iron, including those with diabetic ketoacidosis (DKA), are uniquely susceptible to mucormycosis, we sought to define the role of iron and glucose in regulating the expression of such a receptor. Here, we have identified glucose-regulated protein 78 (GRP78) as what we believe to be a novel host receptor that mediates invasion and damage of human endothelial cells by Rhizopus oryzae, the most common etiologic species of Mucorales, but not Candida albicans or Aspergillus fumigatus. Elevated concentrations of glucose and iron, consistent with those seen during DKA, enhanced GRP78 expression and the resulting R. oryzae invasion and damage of endothelial cells in a receptor-dependent manner. Mice with DKA, which have enhanced susceptibility to mucormycosis, exhibited increased expression of GRP78 in sinus, lungs, and brain compared with normal mice. Finally, GRP78-specific immune serum protected mice with DKA from mucormycosis. These results suggest a unique susceptibility of patients with DKA to mucormycosis and provide a foundation for the development of new therapeutic interventions for these deadly infections.

Authors

Mingfu Liu, Brad Spellberg, Quynh T. Phan, Yue Fu, Yong Fu, Amy S. Lee, John E. Edwards Jr., Scott G. Filler, Ashraf S. Ibrahim

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Figure 1

Endothelial cell surface GRP78 binds to Mucorales germlings.

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Endothelial cell surface GRP78 binds to Mucorales germlings. (A) Endothe...
(A) Endothelial cell surface proteins were labeled with NHS-biotin (5) and then extracted with n-octyl-β-d-glucopyranoside in PBS containing Ca2+ and Mg2+ and protease inhibitors. The labeled proteins (250 μg) were incubated with germlings (2 × 108) of R. oryzae, then the unbound proteins were removed by extensive rinsing with PBS containing Ca2+ and Mg2+. The membrane proteins that remained bound to the organisms were eluted with 6 M urea, separated on 10% SDS-PAGE, and identified by immunoblotting with an anti-biotin monoclonal Ab. Proteins from another SDS-PAGE were stained with SYPRO Ruby and the bands excised for sequencing. (B) The same membrane that was probed with anti-biotin Ab was stripped and then probed with anti-GRP78 Ab. (C) R. oryzae spores were germinated as previously described (4) for different time intervals, and binding to endothelial cell surface protein and immunoblotting against anti-GRP78 Ab were carried out as in A and B and compared with an equal volume of R. oryzae spores (8 × 108). (D) An immunoblot of endothelial cell surface proteins bound to different Mucorales was developed with an anti-GRP78 Ab. Total membrane, total endothelial cell membrane proteins; M, molecular weight marker.