Corrected by: Pseudolaric Acid Analogs as a New Class of Peroxisome Proliferator-Activated Receptor AgonistsPlanta Med 2003; 69(08): 784-784DOI: 10.1055/s-2003-42798
A large heterogeneous family of RNAs derived from a single rat gene contains members that differ from each other at one or more of three positions. Their 5' ends are nested and transcription can begin at 22 or more sites covering 265 nucleotides. Many of the 5' ends are detectable only in brain RNAs, and even 5' ends common with other tissues appear with different absolute and relative abundances in brain RNA. The central portions of the RNAs are of two forms, differing only by the presence or absence of 17 nucleotides; these forms are probably produced by alternative splicing. Polyadenylation occurs at either of two sites. This complicated family of 88 RNAs encodes two novel putative proteins that differ at their C termini.
Immunoglobulin (Ig) heavy (H) and light (L) chain variable (V) region genes are assembled somatically during B-cell differentiation by stage-specific DNA rearrangements of multiple V, diversity (D, H chains only), and joining (J) germline gene segments (reviewed by Alt et al, 1986). Different combinations and imprecise joining of V, D and J elements, random insertion of nucleotides during the joining process (N regions), as well as somatic mutation, contribute to the generation of antibody diversity and ultimately determine the specificity (self or non-self antigen) of a given antibody. Murine lupus is characterised by high titres of circulating autoantibodies (AAb) leading to immune complex mediated lesions (Theofilopoulos and Dixon, 1985). We have previously shown, by means of restriction fragment length polymorphism analysis, that lupus mice and non-lupus mice of the same haplotypes share highly conserved H chain variable region loci (Kofler et al., 1985b). In the present study, we report a detailed analysis of nucleotide sequences corresponding to H and L chains of nine monoclonal AAb with different specificities frequently expressed during lupus disease (single stranded DNA, histone and various Ig isotypes). The following questions were addressed: Arc there any primary structures common to ail AAb regardless of their specificity, which might signal their autoreactive nature? Do AAb employ Ig genes in a restricted manner and are there unique Ig genes different from the germline pool used in the response to exogenous antigens? To what extent is self-specificity germline encoded or acquired during B-cell development?
The TSC1 and TSC2 proteins, which function as a TSC1/TSC2 tumor suppressor complex, are associated with lymphangioleiomyomatosis (LAM), a genetic disorder characterized by the abnormal growth of smooth muscle-like cells in the lungs. The precise molecular mechanisms that modulate LAM cell growth remain unknown. We demonstrate that TSC2 regulates LAM cell growth. Cells dissociated from LAM nodules from the lungs of five different patients with LAM have constitutively activated S6K1, hyperphosphorylated ribosomal protein S6, activated Erk, and increased DNA synthesis compared with normal cells from the same patients. These effects were augmented by PDGF stimulation. Akt activity was unchanged in LAM cells. Rapamycin, a specific S6K1 inhibitor, abolished increased LAM cell growth. The full-length TSC2 was necessary for inhibition of S6 hyperphosphorylation and DNA synthesis in LAM cells, as demonstrated by co-microinjection of the C-terminus, which contains the GTPase activating protein homology domain, and the N-terminus, which binds TSC1. Our data demonstrate that increased LAM cell growth is associated with constitutive S6K1 activation, which is extinguishable by TSC2 expression. Loss of TSC2 GAP activity or disruption of the TSC1/TSC2 complex dysregulates S6K1 activation, which leads to abnormal cell proliferation associated with LAM disease.
The mouse model system was used to evaluate age-associated changes in the subset composition and function of the splenic CD8+ T cell pool. In response to stimulation with plate-bound anti-CD3 epsilon mAb, CD8+ cells from old C57BL/6NNia mice produced greater levels of IFN-gamma than cells from young-adult controls. This age-associated difference was apparent at the levels of both IFN-gamma mRNA accumulation and cytokine release, and was established within the first major cell cycle in culture. In addition, the capacity to produce IFN-gamma appeared to increase gradually with age as evidenced by studies on CD8+ cells from intermediate aged mice. In contrast to these findings, the peak S-phase responses by stimulated CD8+ cells from old mice were significantly reduced relative to young-adult controls. Immunophenotypic analyses of membrane CD44, CD45RB, 3G11, and MEL-14 expression by splenic CD8+ cells from young-adult, intermediate-aged, and old mice revealed an age-associated decrease in the frequencies of cells that expressed low levels of CD44 and high levels of CD45RB, 3G11, and MEL-14, whereas the reciprocal phenotypes increased with age. The correlated analysis of all four subset markers identified a composite phenotype (CD44loCD45RBhiMEL-14hi3G11lo/hi) which, based on past functional studies, is a candidate phenotype for naive cells. This "naive" phenotype dominated the CD8+ cell pool of young-adult mice but decreased in frequency with age. In contrast to the CD44lo cell group, the CD44hi cell fraction, which is associated with preactivated/memory CD8+ cells, was found to be uniformly 3G11lo but expressed heterogeneous levels of CD45RB and MEL-14, perhaps defining multiple subsets within the memory population. All of these latter subsets increased in frequency with age. Finally, we found that when CD8+ cells were fractionated based on CD44 expression the capacity to release measurable levels of IFN-gamma segregated entirely with the CD44hi fraction, irrespective of donor age. Together, these findings support the hypothesis that aging is accompanied by dramatic shifts in the subset compositions of splenic CD8+ cell pools, which contribute significantly to their increased capacity to produce IFN-gamma at the population level.
