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Trafficking of MHC class II in dendritic cells is dependent on but not regulated by degradation of its associated invariant chain.
Traffic. 2010 Mar; 11(3):324-31
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18 Jan 2010
Confirmation, Technical Advance
DOI: 10.3410/f.1489956.971054
The authors warn that certain culture conditions can artificially increase the pH and alter protease activity of the endocytic route. This may be the cause of controversial findings pertaining to the regulation of endosomal pH and antigen presentation by dendritic cells (DCs).
Medium supplemented with...Continue reading
Medium supplemented with...Continue reading
The authors warn that certain culture conditions can artificially increase the pH and alter protease activity of the endocytic route. This may be the cause of controversial findings pertaining to the regulation of endosomal pH and antigen presentation by dendritic cells (DCs).
Medium supplemented with glutamine (Gln) accumulates NH4Cl, which artificially raises the endosomal pH of cells in culture. The authors illustrate the consequences of this effect by analyzing the kinetics of MHC II-associated invariant chain (Ii) degradation (a process influenced by endosomal pH) and MHC II ubiquitination (which requires Ii proteolysis) in DCs. The results demonstrate that Gln decomposition alters these two processes. This study contributes to solve some long-standing controversies in the fields of antigen presentation and DC biology by demonstrating that reported changes in Ii degradation and endosomal pH during DC activation may be due to Gln decomposition. The importance of this paper extends to other studies of biological phenomena in which the regulation of endosomal pH and protease activity is relevant. The authors provide recommendations to prevent the formation of Gln decomposition products.
Medium supplemented with glutamine (Gln) accumulates NH4Cl, which artificially raises the endosomal pH of cells in culture. The authors illustrate the consequences of this effect by analyzing the kinetics of MHC II-associated invariant chain (Ii) degradation (a process influenced by endosomal pH) and MHC II ubiquitination (which requires Ii proteolysis) in DCs. The results demonstrate that Gln decomposition alters these two processes. This study contributes to solve some long-standing controversies in the fields of antigen presentation and DC biology by demonstrating that reported changes in Ii degradation and endosomal pH during DC activation may be due to Gln decomposition. The importance of this paper extends to other studies of biological phenomena in which the regulation of endosomal pH and protease activity is relevant. The authors provide recommendations to prevent the formation of Gln decomposition products.
Disclosures
None declared
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Villadangos J: F1000Prime Recommendation of [ten Broeke T et al., Traffic 2010, 11(3):324-31]. In F1000Prime, 18 Jan 2010; DOI: 10.3410/f.1489956.971054. F1000Prime.com/1489956#eval971054
F1000Prime Recommendations, Dissents and Comments for [ten Broeke T et al., Traffic 2010, 11(3):324-31]. In F1000Prime, 24 May 2013; F1000Prime.com/1489956
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In dendritic cells (DC), newly synthesized MHCII is directed to endosomes by its associated invariant chain (Ii). Here, Ii is degraded after which MHCII is loaded with peptides. In immature DC, ubiquitination of peptide-loaded MHCII drives its sorting to lysosomes for degradation. Ubiquitination of MHCII is strongly reduced in response to inflammatory stimuli, resulting in increased expression of MHCII at the plasma membrane. Whether surface exposure of MHCII is also regulated during DC maturation by changing the rate of Ii degradation remained unresolved by conflicting results in the literature. We here pinpoint experimental problems that have contributed to these controversies and demonstrate that immature and mature DC degrade Ii equally efficient at proper culture conditions. Only when DC were cultured in glutamine containing media, endosome acidification and Ii degradation were restricted in immature DC and enhanced in response to lipopolysaccharide (LPS). These effects are caused by ammonia, a glutamine decomposition product. This artificial behavior could be prevented by culturing DC in media containing a stable dipeptide as glutamine source. We conclude that Ii degradation is a prerequisite for but not a rate limiting step in MHCII processing.
DOI: 10.1111/j.1600-0854.2009.01024.x
PMID: 20051049
