|
|
||||||||
CUTTING EDGE |




* Committee on Immunology, University of Chicago, Chicago, IL 60637;
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037;
MD Anderson Cancer Center, University of Texas, Houston, TX 77030; and
Department of Chemistry, Brigham Young University, Provo UT 84602
| Abstract |
|---|
|
|
|---|
14-J
18 NKT cells, a major population of CD1d-restricted T cells that is conserved in humans. NPC1-deficient mice also exhibited marked defects in the presentation of Sphingomonas cell wall Ags to NKT cells and in bacterial clearance in vivo. A synthetic fluorescent
-glycosylceramide analog of the Sphingomonas Ag trafficked to the lysosome of wild-type cells but accumulated in the late endosome of NPC1-deficient cells. These findings reveal a blockade of lipid trafficking between endosome and lysosome as a consequence of NPC1 deficiency and suggest a common mechanism for the defects in lipid presentation and development of V
14-J
18 NKT cells. | Introduction |
|---|
|
|
|---|
Lipid transport is essential to the processing and presentation of lipid Ags to CD1-restricted T lymphocytes. The CD1 family of glycoproteins is composed of MHC-like,
2-microglobulin-associated glycoproteins that specialize in the capture and presentation of self and microbial glycolipid and lipopeptide Ags to T cells (11, 12). Several lipid transfer proteins (LTPs) have been shown recently to be involved in CD1-mediated lipid Ags presentation. Saposins, a family of LTPs involved in lysosomal GSL degradation (13), also perform essential lipid exchange reactions between membranes and CD1 proteins (14, 15, 16). In the mouse system, where CD1d is the only CD1 family member, prosaposin-deficient mice lacked V
14-J
18 NKT cells, a specialized subset of T cells with dual specificity for the self GSL isoglobotrihexosylceramide (iGb3) (17) and for microbial
-glycuronosylceramides (18, 19, 20). Microsomal triglyceride transfer protein was recently suggested to function in the CD1 pathway as well, based on alterations of CD1d trafficking and NKT cell function in conditional mutant mice (21, 22). Thus, the uptake and trafficking of lipids and their processing and loading onto CD1 molecule may rely on a set of preexisting proteins already involved in general lipid metabolism. In this study, we have examined CD1-mediated lipid presentation in mutant mice and cells lacking NPC1.
| Materials and Methods |
|---|
|
|
|---|
BALB/cNctr-Npc1m1N/J mice were obtained from The Jackson Laboratory. Littermates obtained from heterozygous matings were genotyped by PCR and used for comparative analysis. CD1d/ mice were in the C57BL/6 background (23). All mice were raised in a specific pathogen-free environment at the University of Chicago, according to the Institutional Animal Care and Use Committee guidelines.
Cell culture
Fresh thymocytes, splenocytes, and cultured bone marrow-derived dendritic cells (BMDCs) were obtained as described (24). Parental JP17 and NPC1-mutant A101 Chinese hamster ovary (CHO) cells were a gift from K. Higaki (Faculty of Medicine, Tottori University, Yonago, Japan) (25).
Flow cytometry
CD1d-
-galactosylceramide (
-GC) tetramers were generated and used as described (26). PE-conjugated anti-CD1d Abs were obtained from BD Pharmingen. Flow cytometry was performed as described with FACSCalibur (BD Biosciences), and data were analyzed using CellQuest Pro software (BD Biosciences).
T cell hybridoma stimulation assay
NKT hybridomas included the V
14-J
18 DN32.D3 and the non-V
14 TCB11 and TBD7 clones. Stimulation of 5 x 104 hybridoma cells with fresh thymocytes (5 x 105), splenocytes (5 x 105), or with BMDCs (5 x 104) was as described (17). CHO cells were used at 5 x 104 per well. IL-2 released in cultured supernatants was measured using CTLL-2 indicator cells as described (27).
Bacterial stimulation assay
Sphingomonas paucimobilis (ATCC 29837) was grown in Mueller-Hinton Agar as described (19). Heat kill of bacteria was by exposure to 74°C for 2 h. A total of 5 x 1055 x106 CFU equivalent were added per well containing BMDCs (5 x 104) for stimulation of the DN32.D3 hybridoma.
Live infection
S. paucimobilis was grown for 8 h at 37°C to an OD600 of 0.5, washed, and diluted in PBS. NPC1+/+ and NPC1/ littermates were injected i.v. with 1 x 107 bacteria in 100 µl. Twenty-four hours after infection, bacterial counts were performed after tissue homogenization of liver and spleen in 0.5% Triton X-100 and serial dilution of the homogenate in Mueller-Hinton broth before culture.
Confocal microscopy
To study lipid trafficking, cells were incubated with 5 µM N-(5-(5,7-dimethylborondipyrromethenediflouride)-1-pentanoyl)D-lactosphingosine (BODIPY)-LacCer (Molecular Probes) or with 9 µM prodan-conjugated
-GC (PBS10) (28) at 37°C, for 1 h or overnight, respectively. Cells were directly analyzed by confocal microscopy or fixed before staining with Abs as described (14). When cells were fixed, slides were examined by confocal microscopy without delay to minimize the leakage of lipids out of their original compartment. LysoTracker Red DND-99 (Molecular Probes) was titrated to 1/104 dilution for 5 min on DCs, and 1/4 x 103 dilution for 30 min on CHO cells to stain lysosomes exclusively. The following Abs were used: anti-M6PR IgY Abs, Cy5-conjugated goat anti-chicken IgY (Abcam); Armenian hamster anti-mouse saposin B and saposin C (used as a mixture; N.S. and L.T., manuscript in preparation); and FITC-conjugated goat anti-Armenian hamster IgG (Jackson ImmunoResearch Laboratories). Cells were examined by confocal microscopy using a confocal microscope (TCS SP2 AOBS; Leica), with a 63X NA1.4 oil objective lens, at room temperature.
| Results and Discussion |
|---|
|
|
|---|
14-J
18 NKT cells, compared with NPC+/+ littermates. This NKT cells deficiency was comparable to that of CD1d/ mice, both in the thymus and the spleen, as judged by specific staining with CD1d tetramers loaded with the synthetic agonist ligand of NKT cells,
-GC (Fig. 1A). The NKT cell defect was specific as judged by the normal composition of the CD4, CD8, and B cell compartments (data not shown). The stimulation of the V
14-J
18 NKT hybridoma DN32.D3 by natural lipid ligands on the surface of thymocytes, such as CD1diGb3 complexes (17), was impaired (Fig. 1B). In contrast, the stimulation of control, non-V
14 hybridomas such as TCB11 and TBD7, which recognize unidentified ligands loaded outside of the endosomal/lysosomal compartment (23), was preserved (Fig. 1B), as was CD1d expression in relevant cell types such as thymocytes, splenocytes, and DCs (Fig. 1C).
|
1,2 Gal
Cer, a diglycosylated variant of
-GC that requires lysosomal processing into
GC before recognition by NKT cells, was massively impaired. Presentation of
-GC was less impaired, likely because it can also load CD1d outside of the lysosomal compartment. In these experiments, due to low levels of CD1d expression by DN32.D3, some residual stimulation was observed even in the presence of CD1d-deficient APCs.
In vivo clearance of Sphingomonas, a Gram-negative bacterium expressing
GC NKT ligands instead of LPS in its cell wall, was profoundly impaired (Fig. 2A), consistent with the role of V
14-J
18 NKT cells in detecting and rejecting this class of bacteria (19, 20). Upon in vitro exposure to heat-killed or live Sphingomonas, NPC1/ BMDCs failed to activate the V
14-J
18 NKT hybridoma DN32.D3 (Fig. 2B), further suggesting the presence of defects in lipid presentation to the immune system.
|
1,4 Glc
1,1 Ceramide) with a short acyl chain tagged with BODIPY (BODIPY-LacCer) (34), which normally accumulates in the Golgi of WT cells, was broadly used in recent years to demonstrate retention of GSLs in endosomal compartments of NPC1-deficient CHO cells and human fibroblasts (9, 35, 36). Consistent with these reports, we observed that exogenously administered BODIPY-LacCer rapidly reached the Golgi in BMDCs derived from wild-type mice but markedly accumulated in endosomal compartments of NPC1-deficient cells (data not shown).
We recently reported the synthesis of PBS10, an
-GC mimic of the microbial NKT ligands, where we appended the fluorophore prodan to the carbohydrate in C6" (Fig. 3A). PBS10 binds CD1d and is recognized by NKT cells in a manner similar to the unaltered microbial ligands themselves, or to the synthetic
GC (28). In wild-type DCs, PBS10 clearly accumulated in the lysosomal compartment as shown by the extensive colocalization with the lysosomal marker LysoTracker Red (Fig. 3A). In these experiments, LysoTracker Red was used under conditions that stained the lysosome and excluded the LE. Lysosomal accumulation was further confirmed by colocalization with LAMP-1, but not with the LE marker mannose 6 phosphate receptor (M6PR) (data not shown). Thus, in contrast with BODIPY-LacCer, PBS10 provided a unique tool to examine lipid transport from LE to lysosome, which is considered to be the relevant pathway for the presentation of endogenous and bacterial ligands to V
14 NKT cells (14, 15, 16, 17, 37, 38, 39). Remarkably, PBS10 consistently failed to reach the lysosome of NPC1-deficient cell over a time course of up to 24 h (Fig. 3A). Instead, PBS10 accumulated in the M6PR+ LE compartment (Fig. 4B and data not shown), indicating that the NPC1 deficiency is associated with a more general blockade of lipid exit out of the LE than previously appreciated.
|
|
The precise function of NPC1 in lipid transport remains uncharacterized. Interestingly, however, it has been suggested that lipid accumulation per se, independently of the NPC1 mutation, could constitute a self-aggravating disorder (40). To test this possibility, we used N-butyldeoxygalactonojirimycin (NB-DGJ), a compound that ameliorates lipid storage disease by inhibiting the synthesis of GSLs, to test this possibility. NB-DGJ was shown previously to restore the Golgi transport of BODIPY-LacCer accumulated in endosomal compartment of NPC1-deficient cells (40, 41). Because NB-DGJ exhibited toxicity against BMDCs at pharmacological doses (data not shown), we used the CHO cell line A101 carrying the NPC1 gene inactivated by retroviral gene trap mutagenesis and the parent line JP17 as a model (25). As expected, PBS10 accumulated in the lysosomal compartment of wild-type JP17 cells, as shown by colocalization with LysoTracker Red, but failed to reach the lysosome in NPC1-deficient A101 cells (Fig. 4A, upper panels). Instead, like BODIPY-LacCer, PBS10 accumulated in the M6PR+ LE compartment of A101 cells (Fig. 4B). Interestingly, after treatment with NB-DGJ for 48 h, we could detect a modest but consistent restoration of lysosomal transport of PBS10 (yellow) in A101 cells at the highest doses of inhibitor (Fig. 4A, lower panels). This finding suggests that the lack of NPC1 does not completely abrogate GSL transport to the lysosome and supports the notion that GSLs and cholesterol accumulation in NPC1-deficient cells also contribute to some degree to the blockade of the NKT ligand PBS10 in the LE.
Altogether, these results demonstrate a developmental loss of NKT cells in mice lacking the lipid transporter NPC1 and identify a block in GSL transport from LE to lysosome as a previously undocumented effect of the mutation and a potential mechanism underlying defects in natural and bacterial GSL ligand presentation by CD1d. Future studies in human are warranted to determine whether patients harboring NPC1 mutations also exhibit such unexpected immunological phenotype.
| Acknowledgments |
|---|
| Disclosures |
|---|
|
|
|---|
| Footnotes |
|---|
1 This work was supported by National Institutes of Health Grants AI38339 (to A.B.) and PO1AI053725 (to A.B., P.B.S., and L.T.), and Cancer Research Institute Fellowships (to Y.S. and D.Z.). A.B. is a Howard Hughes Medical Institute Investigator. ![]()
2 Address correspondence and reprint requests to Dr. Albert Bendelac, Department of Pathology, AMB P309, MC1089, University of Chicago, Chicago, IL 60637. E-mail address: abendela{at}bsd.uchicago.edu ![]()
3 Abbreviations used in this paper: NPC1, Niemann-Pick Type C1; GSL, glycosphingolipid; LE, late endosome; LTP, lipid transfer protein; iGb3, isoglobotrihexosylceramide; BMDC, bone marrow-derived dendritic cell; CHO, Chinese hamster ovary;
-GC,
-galactosylceramide; NB-DGJ, N-butyldeoxygalactonojirimycin; BODIPY-LacCer, N-(5-(5,7-dimethylboron-dipyrromethenediflouride)-1-pentanoyl)D-lactosphingosine. ![]()
Received for publication April 3, 2006. Accepted for publication May 9, 2006.
| References |
|---|
|
|
|---|
-D-glucosylceramide synthase deficiency. Proc. Natl. Acad. Sci. USA 100: 1849-1854. This article has been cited by other articles:
![]() |
H. Sikder, Y. Zhao, A. Balato, A. Chapoval, R. Fishelevich, P. Gade, I. S. Singh, D. V. Kalvakolanu, P. F. Johnson, and A. A. Gaspari A Central Role for Transcription Factor C/EBP-{beta} in Regulating CD1d Gene Expression in Human Keratinocytes J. Immunol., August 1, 2009; 183(3): 1657 - 1666. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. L. Schnabl, M. Larcelet, A. B. R. Thomson, and M. T. Clandinin Uptake and fate of ganglioside GD3 in human intestinal Caco-2 cells Am J Physiol Gastrointest Liver Physiol, July 1, 2009; 297(1): G52 - G59. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Bai, Y. Sagiv, Y. Liu, S. Freigang, K. O. A. Yu, L. Teyton, S. A. Porcelli, P. B. Savage, and A. Bendelac Lysosomal recycling terminates CD1d-mediated presentation of short and polyunsaturated variants of the NKT cell lipid antigen {alpha}GalCer PNAS, June 23, 2009; 106(25): 10254 - 10259. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M. Fletcher, M. A. Jordan, S. L. Snelgrove, R. M. Slattery, F. D. Dufour, K. Kyparissoudis, G. S. Besra, D. I. Godfrey, and A. G. Baxter Congenic Analysis of the NKT Cell Control Gene Nkt2 Implicates the Peroxisomal Protein Pxmp4 J. Immunol., September 1, 2008; 181(5): 3400 - 3412. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. D. Wesley, M. S. Tessmer, C. Paget, F. Trottein, and L. Brossay A Y Chromosome-Linked Factor Impairs NK T Development J. Immunol., September 15, 2007; 179(6): 3480 - 3487. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. Schrantz, Y. Sagiv, Y. Liu, P. B. Savage, A. Bendelac, and L. Teyton The Niemann-Pick type C2 protein loads isoglobotrihexosylceramide onto CD1d molecules and contributes to the thymic selection of NKT cells J. Exp. Med., April 16, 2007; 204(4): 841 - 852. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Sagiv, L. Bai, D. G. Wei, R. Agami, P. B. Savage, L. Teyton, and A. Bendelac A distal effect of microsomal triglyceride transfer protein deficiency on the lysosomal recycling of CD1d J. Exp. Med., April 16, 2007; 204(4): 921 - 928. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. O. Speak, M. Salio, D. C. A. Neville, J. Fontaine, D. A. Priestman, N. Platt, T. Heare, T. D. Butters, R. A. Dwek, F. Trottein, et al. From the Cover: Implications for invariant natural killer T cell ligands due to the restricted presence of isoglobotrihexosylceramide in mammals PNAS, April 3, 2007; 104(14): 5971 - 5976. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Porubsky, A. O. Speak, B. Luckow, V. Cerundolo, F. M. Platt, and H.-J. Grone From the Cover: Normal development and function of invariant natural killer T cells in mice with isoglobotrihexosylceramide (iGb3) deficiency PNAS, April 3, 2007; 104(14): 5977 - 5982. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. K. Dougan, P. Rava, M. M. Hussain, and R. S. Blumberg MTP regulated by an alternate promoter is essential for NKT cell development J. Exp. Med., March 19, 2007; 204(3): 533 - 545. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. D. Gadola, J. D. Silk, A. Jeans, P. A. Illarionov, M. Salio, G. S. Besra, R. Dwek, T. D. Butters, F. M. Platt, and V. Cerundolo Impaired selection of invariant natural killer T cells in diverse mouse models of glycosphingolipid lysosomal storage diseases J. Exp. Med., October 2, 2006; 203(10): 2293 - 2303. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |