ABSTRACT
Carcinoembryonic antigen cell adhesion molecule like I (CEACAM1) is expressed on activated T cells and signals through either a long (L) cytoplasmic tail containing immune receptor tyrosine based inhibitory motifs, which provide inhibitory function, or a short (S) cytoplasmic tail with an unknown role. Previous studies on peripheral T cells show that CEACAM1-L isoforms predominate with little to no detectable CEACAM1-S isoforms in mouse and human. We show here that this was not the case in tissue resident T cells of intestines and gut associated lymphoid tissues, which demonstrated predominant expression of CEACAM1-S isoforms relative to CEACAM1-L isoforms in human and mouse. This tissue resident predominance of CEACAM1-S expression was determined by the intestinal environment where it served a stimulatory function leading to the regulation of T cell subsets associated with the generation of secretory IgA immunity, the regulation of mucosal commensalism, and defense of the barrier against enteropathogens.
Subject(s)
Carcinoembryonic Antigen/immunology , Immunity, Mucosal/immunology , Intestines/immunology , T-Lymphocytes/immunology , Amino Acid Motifs/genetics , Amino Acid Motifs/immunology , Animals , Carcinoembryonic Antigen/genetics , Carcinoembryonic Antigen/metabolism , Cytoplasm/genetics , Cytoplasm/immunology , Cytoplasm/metabolism , Homeostasis , Immunity, Mucosal/genetics , Immunoglobulin A/genetics , Immunoglobulin A/immunology , Immunoglobulin A/metabolism , Intestinal Mucosa/metabolism , Listeria monocytogenes/immunology , Listeriosis/immunology , Lymphocyte Activation , Metagenome/immunology , Mice , Mice, Inbred C57BL , NFATC Transcription Factors/genetics , NFATC Transcription Factors/metabolism , Protein Isoforms , Receptors, Immunologic/genetics , Receptors, Immunologic/immunology , Receptors, Immunologic/metabolism , T-Lymphocytes/metabolism , Tyrosine/genetics , Tyrosine/immunology , Tyrosine/metabolismABSTRACT
The multiresistance transposon Tn1331, which mediates resistance to several aminoglycosides and beta-lactams, includes the aac(6')-Ib, aadA1, bla(OXA-9), and bla(TEM-1) genes. The nucleotide sequence of aac(6')-Ib includes a region identical to that of the bla(TEM-1) gene. This region encompasses the promoter and the initiation codon followed by 15 nucleotides. Since there were three possible translation initiation sites, the amino acid sequence at the N terminus of the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib] was determined and was found to be SIQHF. This result indicated that aac(6')-Ib includes a translational fusion: the first five amino acids of the leader peptide of the TEM beta-lactamase are fused to the rest of the AAC(6')-Ib protein. This gene fusion could have formed during the genesis of Tn1331 as a consequence of the generation of a 520-nucleotide duplication (M. E. Tolmasky, Plasmid 24:218-226, 1990). An identical gene isolated from a Serratia marcescens strain has been previously described (G. Tran van Nhieu and E. Collatz, J. Bacteriol. 169:5708-5714, 1987). Extraction of the periplasmic proteins of E. coli harboring aac(6')-Ib by spheroplast formation showed that most of the AAC(6')-Ib protein is present in the cytoplasm. A genetic fusion to phoA confirmed these results. AAC(6')-Ib was shown to be evenly distributed inside the cell's cytoplasm by fluorescent microscopy with an AAC(6')-Ib-cyan fluorescent protein fusion.
Subject(s)
Acetyltransferases/genetics , Cytoplasm/enzymology , Escherichia coli/enzymology , Alkaline Phosphatase/metabolism , Bacterial Proteins/metabolism , DNA, Bacterial/genetics , Immunoblotting , Microscopy, Fluorescence , Molecular Sequence Data , Plasmids/genetics , Subcellular Fractions/enzymologyABSTRACT
Xer-mediated dimer resolution at the mwr site of plasmid pJHCMW1 is osmoregulated in Escherichia coli. Whereas under low-salt conditions, the site-specific recombination reaction is efficient, under high-salt conditions, it proceeds inefficiently. Regulation of dimer resolution is independent of H-NS and is mediated by changes in osmolarity rather than ionic effects. The low level of recombination at high salt concentrations can be overcome by high levels of PepA or by mutating the ARG box to a sequence closer to the E. coli ARG box consensus. The central region of the mwr core recombination site plays a role in regulation of site-specific recombination by the osmotic pressure of the medium.
