Biomedical subjects

Ilaria Potolicchio

Publications and source records attributed to Ilaria Potolicchio.

5 recordsLinked to original sources

PubMed2005

MHC class II compartment subtypes: structure and function.

Reports from the past couple of years point to an emerging association of the biogenesis, composition and ultrastructural morphology of MHC class II compartments (MIICs) with their functions in antigen processing and loading. Growth factors and cytokines involved in dendritic cell maturation have been shown to regulate MIIC biogenesis, and the MHC-class-II-associated invariant chain chaperone has been reported to regulate endosomal morphology and vacuolation. Differences among ultrastructurally distinct MIICs have begun to be appreciated with regard to variation in antigen loading capacity and to polarization of MHC class II conformational variants among different compartments. Finally, the MIIC ultrastructure organizes the mechanism of MHC class II surface trafficking. Together, these findings begin to shed light on the connection between MIIC protein content, MIIC morphology and MHC class II-related antigen processing.

Animals↗

PubMed2005

Conformational variation of surface class II MHC proteins during myeloid dendritic cell differentiation accompanies structural changes in lysosomal MIIC.

Dendritic cells (DC), uniquely among APC, express an open/empty conformation of MHC class II (MHC-II) proteins (correctly folded molecules lacking bound peptides). Generation and trafficking of empty HLA-DR during DC differentiation are investigated here. HLA-DR did not fold as an empty molecule in the endoplasmic reticulum/trans-Golgi network, did not derived from MHC/Ii complexes trafficking to the cell surface, but was generated after invariant chain degradation within lysosomal-like MHC-II rich compartments (MIIC). In pre-DC, generated from monocytes cultured in the presence of GM-CSF, Lamp-1(+)MHC-II(+) compartments are predominantly electron dense and, in these cells, empty MHC-II molecules accounts for as much as 20% of total surface HLA-DR. In immature DC, generated in presence of GM-CSF and IL-4, empty HLA-DR reside in multilamellar MIIC, but are scarcely observed at the cell surface. Thus, the morphology/composition of lysosomal MIIC at different DC maturational stages appear important for surface egression or intracellular retention of empty HLA-DR. Ag loading can be achieved for the fraction of empty HLA-DR present in the "peptide-receptive" form. Finally, in vivo, APC-expressing surface empty HLA-DR were found in T cell areas of secondary lymphoid organs.

Amino Acid Sequence↗

PubMed2005

Involvement of caspase-cleaved and intact adaptor protein 1 complex in endosomal remodeling in maturing dendritic cells.

The involvement of the tetrameric adaptor protein 1 (AP-1) complex in protein sorting in intracellular compartments is not yet completely defined. Here we report that in immature dendritic cells, the beta1- and gamma-subunits of AP-1 underwent caspase 3-catalyzed cleavage in their hinge regions, resulting in removal of the C-terminal 'ear' domains. Cleavage was inhibited by lipopolysaccharide or caspase inhibitors, each of which led to maturation of the dendritic cells, demonstrated by endosomal remodeling and an increase in surface expression of peptide-loaded major histocompatibility complex class II. Overexpression of similarly truncated AP-1 together with 'silencing' of the endogenous genes in immature dendritic cells did not compromise delivery of major histocompatibility complex class II invariant chain to endosomal compartments. However, after lipopolysaccharide-induced maturation, overexpression of truncated AP-1 and 'silencing' of endogenous genes did result in the anomalous surface accumulation of invariant chain and the peptide-editing molecule H2-DM. Thus, at least one function for intact AP-1 is to retain some proteins in endosomes during the dendritic cell maturation process in which others are allowed to egress to the cell surface.

Adaptor Protein Complex 1↗

PubMed2005

Proteomic analysis of microglia-derived exosomes: metabolic role of the aminopeptidase CD13 in neuropeptide catabolism.

Vesicle transport is a fundamental mechanism of communication in the CNS. In this study we characterized a novel type of vesicle released by murine brain microglial cells: microglial exosomes. Analysis of their protein content identified several enzymes, chaperones, tetraspanins, and membrane receptors previously reported in B cells and dendritic cell-derived exosomes. Additionally, microglia-derived exosomes expressed the aminopeptidase CD13 and the lactate transporter MCT-1. Exosomal CD13 was metabolically active in cleaving leucine- and methionine-enkephalins peptides by releasing the N-terminal tyrosine. Cleaved neuropeptides were unable to bind to the neuronal opioid receptor as assessed by cAMP response. Microglial exosomal vesicles may represent an important, previously unrecognized, cellular communication system in an organ in which cell motility is highly restricted.

Animals↗

PubMed2003

Molecular interaction and enzymatic activity of macrophage migration inhibitory factor with immunorelevant peptides.

Disulfide reduction is an important step in antigen processing for HLA class II restricted T cell responses. Migration inhibitory factor (MIF) is a member of the thioredoxin family and has been classically defined as a cytokine. Using enzyme-linked immunosorbent assay and CD analysis, here we describe the binding to MIF of two peptides, hepatitis B surface antigen (HBsAg) and insulin B (InsB) with high affinity for HLA class II allo-types, HLA-DP2 and HLA-DQ8, respectively. At neutral pH, cysteinylated InsB was a substrate for MIF thiol reductase activity, as assessed by mass spectroscopy/electrospray analysis. Finally, a biologically active form of MIF co-immunopurified with mature forms of HLA DP2/15, and a peptide derived from the HLA-DP beta1 helix could be used for affinity purification of MIF. The possibility that MIF participates in class II antigen presentation and/or as a chaperone is discussed.

Antigen Presentation↗