scholarly journals Peptide-induced stabilization and intracellular localization of empty HLA class I complexes.

1992 ◽  
Vol 176 (1) ◽  
pp. 147-156 ◽  
Author(s):  
E J Baas ◽  
H M van Santen ◽  
M J Kleijmeer ◽  
H J Geuze ◽  
P J Peters ◽  
...  
Keyword(s):  
Cell Surface ◽  
Cell Line ◽  
Heavy Chain ◽  
Mutant Cell ◽  
Intracellular Localization ◽  
Hla Class I ◽  
Human Cell Line ◽  
Class I ◽  
Acid Extraction ◽  
Beta 2 Microglobulin

The human cell line T2 has been reported to be class I assembly deficient, and accordingly expresses reduced amounts of HLA-A2 and no HLA-B5 at the cell surface. By immunoblotting we observe the steady-state class I heavy chain levels of T2 to be near normal when compared with the identical class I alleles of the wild-type cell line T1. In pulse chase experiments, formation of heavy chain beta 2-microglobulin complexes is observed for both HLA-A2 and HLA-B5. Culture at reduced temperatures (26 or 20 degrees C) does not increase the amount of class I molecules transported, unlike what has been reported for the class I assembly-deficient mouse mutant cell line RMA-S. The HLA-B5 and the HLA-A2 complexes formed by T2 are thermolabile in cell lysates, albeit to different degrees. The thermolability of HLA-B5 can be overcome by addition of HLA-B5-presentable peptides, obtained by trifluoroacetic acid extraction from an HLA-B5-positive cell line, underlining the necessity of peptide for class I stability and indicating that T2-derived class I complexes are devoid of peptide. Cytoplast fusion of T2 cells with RMA-S cells shows the defect in class I assembly of RMA-S to be similar to that of T2. Localization of class I molecules observed by immuno-electron microscopy reveals the accumulation in the T2 cell line of both HLA-B5 and HLA-A2 in the endoplasmic reticulum (ER). Class I molecules are present in all the cisternae of the Golgi complex of T2, but the ratio of HLA-A and -B locus products in the Golgi area differs significantly from that at the cell surface. We conclude that the requirement for peptide in transport of class I molecules manifests itself at a stage beyond the ER, most likely the Golgi area.

scholarly journals Overproduction and secretion of beta 2-microglobulin by a rat thymic epithelial cell line that expresses MHC class I heavy chain

1991 ◽  
Vol 98 (4) ◽  
pp. 559-565
Author(s):  
C. Dargemont ◽  
D. Dunon ◽  
J. Salamero ◽  
M.A. Deugnier ◽  
J. Davoust ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Mhc Class I ◽  
Heavy Chain ◽  
Class I ◽  
Thymic Epithelial Cell ◽  
Epithelial Cell Line ◽  
Beta 2 ◽  
Beta 2 Microglobulin ◽  
Thymic Epithelial Cell Line

Major histocompatibility complex (MHC) class I antigens are constituted of dimers consisting of a peripheral light chain, beta 2-microglobulin (beta 2m) and a transmembrane heavy chain whose cell surface expression depends on its assembly with beta 2m. In contrast, soluble beta 2m can be secreted in the absence of heavy chain expression. The presence of beta 2m in medium conditioned by a rat thymic epithelial cell line, IT45-R1 (IT45) prompted us to investigate whether beta 2m could be secreted by cells that express MHC class I antigens. IT45 cells produce three to five times more beta 2m in the culture supernatant than another rat thymic epithelial cell line, IT26-R21 (IT26). The IT45 cell line exported beta 2m through a constitutive pathway of secretion, as indicated by the kinetics of production and localization of intracellular beta 2m. Although cells from the IT45 cell line expressed a much higher amount of beta 2m as compared to IT26 and NBT II cells (a rat bladder epithelial cell line), all three of these cell lines expressed the same amount of membrane and intracellular MHC class I heavy chain. These data are thus consistent with a constitutive secretion of beta 2m dependent upon an overexpression of MHC class I light chain as compared to the heavy chain. The amount of beta 2m mRNA and the ratio of beta 2m versus MHC class I heavy chain transcripts were higher in IT45 than in IT26 cells, indicating that overexpression of beta 2m in IT45 cells could be due to an enhanced level of beta 2m mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

A subject with a novel type I bare lymphocyte syndrome has tapasin deficiency due to deletion of 4 exons by Alu-mediated recombination

Blood ◽  
2002 ◽  
Vol 100 (4) ◽  
pp. 1496-1498 ◽  
Author(s):  
Toshio Yabe ◽  
Sumiyo Kawamura ◽  
Masako Sato ◽  
Koichi Kashiwase ◽  
Hidenori Tanaka ◽  
...  
Keyword(s):  
Cell Surface ◽  
Heavy Chain ◽  
Antigen Processing ◽  
Hla Class I ◽  
Class I ◽  
Type I ◽  
Bare Lymphocyte Syndrome ◽  
Peptide Loading ◽  
Alu Repeat ◽  
Chain Defects

HLA class I expression depends on the formation of a peptide-loading complex composed of class I heavy chain; β2-microglobulin; the transporter associated with antigen processing (TAP); and tapasin, which links TAP to the heavy chain. Defects in TAP result in a class I deficiency called the type I bare lymphocyte syndrome (BLS). In the present study, we examined a subject with a novel type I BLS who does not exhibit apparent TAP abnormalities but who has a tapasin defect. The subject's TAPASIN gene has a 7.4-kilobase deletion between introns 3 and 7; an Alu repeat–mediated unequal homologous recombination may be the cause of the deletion. No tapasin polypeptide was detected in the subject's cells. The cell surface class I expression level in tapasin-deficient cells was markedly reduced but the reduction was not as profound as in TAP-deficient cells. These results suggest that tapasin deficiency is another cause of type I BLS.

MHC class I molecules are an essential cell surface component involved in Theileria parva sporozoite binding to bovine lymphocytes

1995 ◽  
Vol 108 (4) ◽  
pp. 1587-1596
Author(s):  
M.K. Shaw ◽  
L.G. Tilney ◽  
A.J. Musoke ◽  
A.J. Teale
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Cell Line ◽  
Mhc Class I ◽  
Mutant Cell ◽  
Cell Surface Receptor ◽  
Class I ◽  
Theileria Parva ◽  
Surface Molecules ◽  
Mhc Class I Molecules

The major histocompatibility complex (MHC) class I molecules are ubiquitous cell surface molecules involved in the cell-mediated immune response. We show here, using a number of different, independent approaches, that these proteins are an essential component of the host cell surface receptor involved in Theileria parva sporozoite invasion. Monoclonal antibodies (mAbs) reactive with common determinants on MHC class I molecules and with beta-2 microglobulin inhibited sporozoite entry by specifically preventing the initial binding event. However, in experiments using lymphocytes from heterozygous cattle in which at least four MHC class I gene products are expressed, mAbs which reacted with only one of these products did not inhibit entry. Using a series of bovine deletion mutant cell lines from which one or both MHC class I haplotypes had been lost, sporozoite binding and entry clearly correlated with the level of class I surface expression. While the level of sporozoite entry into cells in which one of the MHC class I haplotypes was lost was only slightly lower than into the parent cells, in a double deletion cell line having less than 5% of the class I expression of the parent cells the level of infection was only 4.3% of that into the parent cells. Furthermore, sporozoite entry into cells from a spontaneously arising mutant cell line exhibiting low levels of class I expression was correspondingly low. Treatment of lymphocytes with IL-2 produced a significant increase in host cell susceptibility and sporozoite entry and this increase correlated with either an increase in the number of target molecules per host cell, or in the binding of bovine MHC class I molecules to the mAbs. In particular, a significant increase in the level of reactivity with mAb W6/32 was observed. Lastly, we show that parasite entry can be competitively inhibited with an isolated sporozoite surface protein, p67. However, p67 binds weakly to lymphocyte surface molecules and initial attempts to use p67 to isolate the relevant host cell molecule(s) have not been successful.

scholarly journals Adenovirus infection inhibits the phosphorylation of major histocompatibility complex class I proteins.

1991 ◽  
Vol 174 (5) ◽  
pp. 1159-1166 ◽  
Author(s):  
R Lippé ◽  
E Luke ◽  
Y T Kuah ◽  
C Lomas ◽  
W A Jefferies
Keyword(s):  
Major Histocompatibility Complex ◽  
Cell Surface ◽  
Cell Line ◽  
Human Cell ◽  
Human Cell Line ◽  
Class I ◽  
Major Histocompatibility ◽  
Mhc Molecules ◽  
Histocompatibility Complex ◽  
Hla Molecules

Major histocompatibility complex (MHC) class I molecules act as peptide receptors to direct the recognition of foreign antigens by cytolytic T cells. The cell surface expression and trafficking of these peptide receptors is thought to be controlled by the conformation of the MHC molecule and possibly by the phosphorylation of the cytoplasmic portion of the heavy chain protein. It is of some interest that adenoviruses (Ads) have evolved proteins that interfere with the expression of MHC molecules. One of these proteins, called E3/19k, binds to newly synthesized MHC molecules in the rough endoplasmic reticulum (RER) and inhibits their trafficking to the cell surface. Here we show that during the infection of a human cell line with Ad2, the phosphorylation of the endogenous MHC molecules is inhibited. We also observe that the phosphorylation of the endogenous HLA molecules is grossly impaired in a human cell line transfected with the Ad2 EcoRI D fragment containing the E3/19k gene. We conclude that the E3/19k protein inhibits the phosphorylation of the MHC heavy chains and that this may be one of the important functions of this protein in infected cells. In addition, we show that a mutant of the E3/19k protein, which lacks an RER retention signal but which retains its ability to bind to HLA molecules, does not inhibit the phosphorylation of HLA molecules and that phosphorylated molecules are not Endo H sensitive. This suggests that HLA molecules are phosphorylated after leaving the medial-Golgi compartment, thus providing the most compelling evidence yet that HLA molecules are phosphorylated at or near the cell surface. Finally, to our knowledge, this is the first study under which the phosphorylation of MHC molecules is shown to be altered and may have some relevance for other pathogenic conditions.

scholarly journals Impaired intracellular transport and cell surface expression of nonpolymorphic HLA-E: evidence for inefficient peptide binding.

1992 ◽  
Vol 176 (4) ◽  
pp. 1083-1090 ◽  
Author(s):  
M Ulbrecht ◽  
J Kellermann ◽  
J P Johnson ◽  
E H Weiss
Keyword(s):  
Cell Surface ◽  
Intracellular Transport ◽  
Hla Class I ◽  
Surface Expression ◽  
Myeloma Cell ◽  
Peptide Ligands ◽  
Class I ◽  
Cell Surface Expression ◽  
Trimolecular Complex ◽  
Beta 2 Microglobulin

The assembly of the classical, polymorphic major histocompatibility complex class I molecules in the endoplasmic reticulum requires the presence of peptide ligands and beta 2-microglobulin (beta 2m). Formation of this trimolecular complex is a prerequisite for efficient transport to the cell surface, where presented peptides are scanned by T lymphocytes. The function of the other class I molecules is in dispute. The human, nonclassical class I gene, HLA-E, was found to be ubiquitously transcribed, whereas cell surface expression was difficult to detect upon transfection. Pulse chase experiments revealed that the HLA-E heavy chain in transfectants, obtained with the murine myeloma cell line P3X63-Ag8.653 (X63), displays a significant reduction in oligosaccharide maturation and intracellular transport compared with HLA-B27 in corresponding transfectants. The accordingly low HLA-E cell surface expression could be significantly enhanced by either reducing the culture temperature or by supplementing the medium with human beta 2m, suggesting inefficient binding of endogenous peptides to HLA-E. To analyze whether HLA-E binds peptides and to identify the corresponding ligands, fractions of acid-extracted material from HLA-E/X63 transfectants were separated by reverse phase HPLC and were tested for their ability to enhance HLA-E cell surface expression. Two fractions specifically increased the HLA class I expression on the HLA-E transfectant clone.

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