Inhibition of macropinocytosis blocks antigen presentation of type II collagen in vitro and in vivoin HLA-DR1 transgenic mice

Abstract

Professional antigen-presenting cells, such as dendritic cells, macrophages and B cells have been implicated in the pathogenesis of rheumatoid arthritis, constituting a possible target for antigen-specific immunotherapy. We addressed the possibility of blocking antigen presentation of the type II collagen (CII)-derived immunodominant arthritogenic epitope CII [259][260][261][262][263][264][265][266][267][268][269][270][271][272][273] to specific CD4 T cells by inhibition of antigen uptake in HLA-DR1-transgenic mice in vitro and in vivo. Electron microscopy, confocal microscopy, subcellular fractionation and antigen presentation assays were used to establish the mechanisms of uptake, intracellular localization and antigen presentation of CII by dendritic cells and macrophages. We show that CII accumulated in membrane fractions of intermediate density corresponding to late endosomes. Treatment of dendritic cells and macrophages with cytochalasin D or amiloride prevented the intracellular appearance of CII and blocked antigen presentation of CII 259-273 to HLA-DR1-restricted T cell hybridomas. The data suggest that CII was taken up by dendritic cells and macrophages predominantly via macropinocytosis. Administration of amiloride in vivo prevented activation of CII-specific polyclonal T cells in the draining popliteal lymph nodes. This study suggests that selective targeting of CII internalization in professional antigen-presenting cells prevents activation of autoimmune T cells, constituting a novel therapeutic strategy for the immunotherapy of rheumatoid arthritis.

A Differential Role for Macropinocytosis in Mediating Entry of the Two Forms of Vaccinia Virus into Dendritic Cells

“…Our study is the first demonstration that EV can enter cells via a mechanism other than fusion with the plasma membrane. These results lay the foundation for further investigations in animal models to determine the significance of DC macropinocytosis of both MV and EV in vaccinia pathogenesis and use of vaccinia recombinants as vaccine candidates, for example, by examining the in vivo effects of amiloride or wortmannin-induced inhibition of macropinocytosis in mice on antigen presentation by various myeloid DC subsets [66]. Further elucidation of the fate of VACV inside DCs will contribute not only to our understanding of the biology of VACV interactions with the immune system but also the efficacy of vaccines employing VACV vectors and should assist their rational design.…”

A Novel Mechanism Is Involved in Cationic Lipid-Mediated Functional siRNA Delivery

“…(38) Treatment of BSC cells with PDMP had no effect on knockdown of target transcript following transfection with siRNA lipoplexes (Figure 4B) although it inhibited the uptake of siRNA lipoplexes by approximately 20% (Figure 4D). Similarly, amiloride, a strong inhibitor of macropinocytosis,(39) showed no significant effect on either the knockdown of CyB transcript or siRNA lipoplex uptake (Figure 4C,D). Together, these results suggest that functional delivery of siRNA lipoplexes does not appear to depend on caveolin- or lipid-raft-mediated endocytosis or macropinocytosis.…”

Physiological role of the interaction between CARMIL1 and capping protein

“…Lamellipodia are important for ruffling at the cell edge and the process of macropinocytosis, in which ruffles close back onto the cell body and engulf extracellular fluid. Macropinocytosis allows cells to sample their environment and take up antigens for processing (von Delwig et al ., 2006). …”