The mouse CD1d cytoplasmic tail mediates CD1d trafficking and antigen presentation by adaptor protein 3-dependent and -independent mechanisms.

The short cytoplasmic tail of mouse CD1d (mCD1d) is required for its endosomal localization, for the presentation of some glycolipid Ags, and for the development of Valpha14i NKT cells. This tail has a four-amino acid Tyr-containing motif, Tyr-Gln-Asp-Ile (YQDI), similar to those sequences known to be important for the interaction with adaptor protein complexes (AP) that mediate the endosomal localization of many different proteins. In fact, mCD1d has been shown previously to interact with the AP-3 adaptor complex.

The adaptor protein AP-3 is required for CD1d-mediated antigen presentation of glycosphingolipids and development of Valpha14i NKT cells.

Relatively little is known about the pathway leading to the presentation of glycolipids by CD1 molecules. Here we show that the adaptor protein complex 3 (AP-3) is required for the efficient presentation of glycolipid antigens that require internalization and processing. AP-3 interacts with mouse CD1d, and cells from mice deficient for AP-3 have increased cell surface levels of CD1d and decreased expression in late endosomes.

NIK-dependent RelB activation defines a unique signaling pathway for the development of V alpha 14i NKT cells.

A defect in RelB, a member of the Rel/nuclear factor (NF)-kappa B family of transcription factors, affects antigen presenting cells and the formation of lymphoid organs, but its role in T lymphocyte differentiation is not well characterized. Here, we show that RelB deficiency in mice leads to a selective decrease of NKT cells. RelB must be expressed in an irradiation-resistant host cell that can be CD1d negative, indicating that the RelB expressing cell does not contribute directly to the positive selection of CD1d-dependent NKT cells.

Embryonic, fetal, and neonatal tongue myoblasts exhibit molecular heterogeneity in vitro.

Variable gene expression patterns have been shown to exist between embryonic, fetal, and neonatal lineages of limb skeletal myoblasts in vitro and in vivo. In this study, we examined the molecular phenotype of embryonic, fetal, and neonatal tongue myoblasts in primary culture for comparison with in vivo developmental tongue myoblasts. Myogenic regulatory factor (MRF) and myosin heavy chain (MHC) gene expression were determined in culture during both growth and differentiation conditions by PCR, immunoblotting, and immunohistochemistry.

Glycolipid antigen processing for presentation by CD1d molecules.

The requirement for processing glycolipid antigens in T cell recognition was examined with mouse CD1d-mediated responses to glycosphingolipids (GSLs). Although some disaccharide GSL antigens can be recognized without processing, the responses to three other antigens, including the disaccharide GSL Gal(alpha1-->2)GalCer (Gal, galactose; GalCer, galactosylceramide), required removal of the terminal sugars to permit interaction with the T cell receptor. A lysosomal enzyme, alpha-galactosidase A, was responsible for the processing of Gal(alpha1-->2)GalCer to generate the antigenic monosaccharide epitope.