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Spatial organization of the transforming MHC class II compartment
Author(s) -
Pannerden Hezder E. Nispen,
Geerts Willie J.,
Kleijmeer Monique J.,
Heijnen Harry F.G.
Publication year - 2010
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1042/bc20100046
Subject(s) - biology , endosome , microbiology and biotechnology , cd74 , cytoskeleton , microfilament , compartment (ship) , golgi apparatus , mhc class i , mhc class ii , biophysics , major histocompatibility complex , cell , intracellular , immunology , biochemistry , antigen , endoplasmic reticulum , oceanography , geology
Background information . DC (dendritic cells) continuously capture pathogens and process them into small peptides within the endolysosomal compartment, the MIIC (MHC class II‐containing compartment). In MIICs peptides are loaded on to MHC class II and rapidly redistributed to the cell surface. This redistribution is accompanied by profound changes of the MIICs into tubular structures. An emerging concept is that MIIC tubulation provides a means to transport MHC class II—peptide complexes to the cell surface, either directly or through vesicular intermediates. To obtain spatial information on the reorganization of the MIICs during DC maturation, we performed electron tomography on cryo‐immobilized and freeze‐substituted mouse DCs after stimulation with LPS (lipopolysaccharide). Results . In non‐stimulated DCs, MIICs are mostly spherical. After 3 h of LPS stimulation, individual MIICs transform into tubular structures. Three‐dimensional reconstruction showed that the MIICs frequently display fusion profiles and after 6 h of LPS stimulation, MIICs become more interconnected, thereby creating large MIIC reticula. Microtubules and microfilaments align these MIICs and reveal physical connections. In our tomograms we also identified a separate population of MIIC‐like intermediates, particularly at extended ends of MIIC tubules and in close proximity to the trans ‐Golgi network. No fusion events were captured between reticular MIICs and the plasma membrane. Conclusions . Our results indicate that MIICs have the capacity to fuse together, whereby the cytoskeleton possibly provides a scaffold for the MIIC shape change and directionality. MIIC‐like intermediates may represent MHC class II carriers.