The 20S Proteasome Is Active in Apoptotic Nanovesicles and Controls Anti-LG3 Antibody Production

M. Dieudé,^1,4 C. Bell,^2,4 J. Turgeon,^1,4 D. Beillevaire,^1,4 K. Hamelin,^1,4 S. Qi,^1,4 N. Pallet,^1,4 C. Rondeau,³ D. Gingras,³ M. Desjardins,³ P. Thibault,^2,4 M.-J. Hébert.^1,4

¹Research Centre, Centre Hospitalier de l'Université
de Montréal (CRCHUM), Montreal, QC, Canada
²Institute for Research in Immunology and Cancer (IRIC), Montreal, QC, Canada
³Université
de Montréal, Montreal, QC, Canada
⁴Canadian National Transplant Research Program (CNTRP), Montreal, Canada.

Meeting: 2015 American Transplant Congress

Abstract number: C8

Keywords: Antibodies, Apoptosis, Autoimmunity, Endothelial cells

Session Information

Session Name: Poster Session C: Antigen Presenting Cells in Alloimmune Responses/B Cells and Antibody in Alloimmune Responses

Session Type: Poster Session

Date: Monday, May 4, 2015

Session Time: 5:30pm-6:30pm

Presentation Time: 5:30pm-6:30pm

Location: Exhibit Hall E

Humoral autoreactivity to apoptotic cells and perlecan/LG3, a proteoglycan fragment released by apoptotic cells, predicts poor allograft outcomes in renal transplant patients. How apoptotic cells can break tolerance to self before transplantation remains ill-defined. Here, we aimed at evaluating whether membrane vesicles (MV) released by apoptotic endothelial cells contribute to auto-immune pathways of importance in allograft survival and rejection.

MV released by apoptotic endothelial cells (apoptotic bodies (apobodies) and apoptotic nanovesicles (apoNano) were purified by sequential centrifugation and analysed by electron microscopy and comparative proteomics. C57Bl/6 mice transplanted with an aortic graft from a MHC-mismatched BALB/c donor or non-transplanted C57Bl/6 mice were injected intravenously with apoptotic MV for up to 3 weeks.

Injection of apobodies (size 500 to 7000 nm), characterized by the presence of histones, failed to induce an immunogenic response. Injection of apoNano (30 to 100nm) characterized by the presence of perlecan/LG3, induced a strong anti-LG3 IgG response, both in non-transplanted (n=11, p<0.001) and transplanted (n=12, p<0.05) mice. Aorta recipients injected with apoNano showed increased neointima formation (n=6, p<0.01), compared to recipients injected with apobodies or vehicle. Proteomic analyses identified all sub-components of the 20S proteasome specifically in apoNano. All three proteolytic activities of the 20S proteasome were significantly increased in apoNano (trypsin-like (p<0.05), chymotrypsin-like (p<0.01) and caspase-like (p<0.01)) compared to apobodies or cell extracts. Proteasome inhibition in endothelial cells with bortezomib, did not reduce the production of apoNano but significantly impeded their proteolytic activity (p<0.001). Injection of proteasome-inhibited apoNano led to reduced circulating levels of anti-LG3 IgG (n=11, p<0.05).

These results identify the 20S proteasome as a novel component of apoptotic nanovesicles and as an important determinant of break in tolerance leading to the production of anti-LG3 antibodies.

To cite this abstract in AMA style:

Dieudé M, Bell C, Turgeon J, Beillevaire D, Hamelin K, Qi S, Pallet N, Rondeau C, Gingras D, Desjardins M, Thibault P, Hébert M-J. The 20S Proteasome Is Active in Apoptotic Nanovesicles and Controls Anti-LG3 Antibody Production [abstract]. Am J Transplant. 2015; 15 (suppl 3). https://atcmeetingabstracts.com/abstract/the-20s-proteasome-is-active-in-apoptotic-nanovesicles-and-controls-anti-lg3-antibody-production/. Accessed May 6, 2025.

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