Analysis of protease activity in live antigen-presenting cells shows regulation of the phagosomal proteolytic contents during dendritic cell activation.
Here, we describe a new approach designed to monitor the proteolytic activity of maturing phagosomes in live antigen-presenting cells. We find that an ingested particle sequentially encounters distinct protease activities during phagosomal maturation. Incorporation of active proteases into the phagosome of the macrophage cell line J774 indicates that phagosome maturation involves progressive fusion with early and late endocytic compartments. In contrast, phagosome biogenesis in bone marrow-derived dendritic cells (DCs) and macrophages preferentially involves endocytic compartments enriched in cathepsin S. Kinetics of phagosomal maturation is faster in macrophages than in DCs. Furthermore, the delivery of active proteases to the phagosome is significantly reduced after the activation of DCs with lipopolysaccharide. This observation is in agreement with the notion that DCs prevent the premature destruction of antigenic determinants to optimize T cell activation. Phagosomal maturation is therefore a tightly regulated process that varies according to the type and differentiation stage of the phagocyte.
Department of Pathology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Ana-Maria
AM
Lennon-Duménil
Arnold H
AH
Bakker
René
R
Maehr
Edda
E
Fiebiger
Herman S
HS
Overkleeft
Mario
M
Rosemblatt
Hidde L
HL
Ploegh
Cécile
C
Lagaudrière-Gesbert
D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D001665:Binding Sites; D002401:Cathepsin B / Q000235:genetics / Q000276:immunology*; D056657:Cathepsin K; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism / Q000494:pharmacology; D003713:Dendritic Cells / Q000201:enzymology* / Q000276:immunology; D015536:Down-Regulation; D007930:Leucine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000276:immunology; D010588:Phagosomes / Q000201:enzymology*
D015853:Cysteine Proteinase Inhibitors; C419228:DCG 04; D008070:Lipopolysaccharides; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L; C534278:Ctsl protein, mouse; C028217:cathepsin S; D056657:Cathepsin K; C534132:Ctsk protein, mouse; D007930:Leucine