Expression of mitochondrial marker proteins during spermatogenesis.
(33/1959)
Spermatogenesis is a highly complex, hormonally regulated cytodifferentiation process finally leading to the production of spermatozoa. In addition to other events germ cell differentiation is characterized by a gradual structural modification of many organelles including mitochondria which play a unique role. The morphological and functional development of germ cell mitochondria is a reflection of the permanent change in the testicular microenvironment which occurs when the germ cells are slowly moving from the base of the seminiferous epithelium to the lumen. Concomitant with the structural changes, several mitochondrial proteins are known to be expressed and synthesized during distinct phases of the organelle's development. This review pays particular attention to these transiently expressed mitochondrial proteins such as hsp60, Lon protease, sulphydryl oxidase and cytochrome ct. Furthermore, the biological function of this stepwise gene activation during mitochondrial and germ cell development is discussed. (+info)
Thermodynamics of nucleotide binding to the chaperonin GroEL studied by isothermal titration calorimetry: evidence for noncooperative nucleotide binding.
(34/1959)
We characterized the thermodynamics of binding reactions of nucleotides ADP and ATPgammaS (a nonhydrolyzable analog of ATP) to GroEL in a temperature range of 5 degrees C to 35 degrees C by isothermal titration calorimetry. Analysis with a noncooperative binding model has shown that the bindings of nucleotides are driven enthalpically with binding constants of 7x103 M-1 and 4x104 M-1 for ADP and ATPgammaS, respectively, at 26 degrees C and that the heat capacity change DeltaCp is about 100 cal/mol.K for both the nucleotides. The stoichiometries of binding were about 8 and 9 molecules for ADP and ATPgammaS, respectively, per GroEL tetradecamer at 5 degrees C, and both increased with temperature to reach about 14 (ADP) and 12 (ATPgammaS) for both nucleotides at 35 degrees C. The absence of initial increase of binding heat as well as Hill coefficient less than 1.2, which were obtained from the fitting to the model curve by assuming positive cooperativity, showed that there was virtually no positive cooperativity in the nucleotide bindings. Incorporating a difference in affinity for the nucleotide (ADP and ATPgammaS) between the two rings of GroEL into the noncooperative binding model improved the goodness of fitting and the difference in the affinity increased with decreasing temperature. (+info)
Binding of polylysine to GroEL. Inhibition of the refolding of mMDH.
(35/1959)
Luminescence techniques have been used to investigate the interaction of GroEL with polylysine tagged with a fluorescent probe. The fluorescence emitted by anthraniloyl-polylysine, upon excitation at 320 nm, is enhanced by the addition of stoichiometric amounts of GroEL. The equilibrium dissociation constant of the complex (Kd=50 nM) was determined by fluorometric titrations. The rate and extent of recovery of the catalytic activity of denatured mitochondrial malate dehydrogenase, assisted by GroEL, is influenced by either polylysine or anthraniloyl-polylysine. It is suggested that interaction of the positively charged poly-amino acid with the apical domain of GroEL prevents binding of the unfolded protein substrate. (+info)
A peptide binding motif for I-Eg7, the MHC class II molecule that protects E alpha-transgenic nonobese diabetic mice from autoimmune diabetes.
(36/1959)
The nonobese diabetic (NOD) mouse, a model of spontaneous insulin-dependent diabetes mellitus (IDDM), fails to express surface MHC class II I-Eg7 molecules due to a deletion in the E alpha gene promoter. E alpha-transgenic NOD mice express the E alpha E beta g7 dimer and fail to develop either insulitis or IDDM. A number of hypotheses have been proposed to explain the mechanisms of protection, most of which require peptide binding to I-Eg7. To define the requirements for peptide binding to I-Eg7, we first identified an I-Eg7-restricted T cell epitope corresponding to the sequence 4-13 of Mycobacterium tuberculosis 65-kDa heat shock protein (hsp). Single amino acid substitutions at individual positions revealed a motif for peptide binding to I-Eg7 characterized by two primary anchors at relative position (p) 1 and 4, and two secondary anchors at p6 and p9. This motif is present in eight of nine hsp peptides that bind to I-Eg7 with high affinity. The I-Eg7 binding motif displays a unique p4 anchor compared with the other known I-E motifs, and major differences are found between I-Eg7 and I-Ag7 binding motifs. Analysis of peptide binding to I-Eg7 and I-Ag7 molecules as well as proliferative responses of draining lymph node cells from hsp-primed NOD and E alpha-transgenic NOD mice to overlapping hsp peptides revealed that the two MHC molecules bind different peptides. Of 80 hsp peptides tested, none bind with high affinity to both MHC molecules, arguing against some of the mechanisms hypothesized to explain protection from IDDM in E alpha-transgenic NOD mice. (+info)
Association of Chlamydia trachomatis heat-shock protein 60 antibody and HLA class II DQ alleles.
(37/1959)
A total of 113 female commercial sex workers had individual alleles for HLA class II genes determined by using labeled sequence-specific oligonucleotide probes to hybridize to polymerase chain reaction products of amplified DNA. Women also had microimmunofluorescent (MIF) antibody titers to Chlamydia trachomatis elementary bodies and ELISA antibody to recombinant chlamydial heat-shock protein 60 (Chsp60) determined. Women were prospectively followed at monthly intervals over 2 years for incident C. trachomatis infection and acute pelvic inflammatory disease (PID). HLA DQA1*0401 and DQB1*0402 alleles were statistically associated with increased prevalence and amount of antibody to Chsp60 but not MIF antibody. However, these alleles did not alter the risk for chlamydial PID. The potential role that HLA DQ may play in chlamydial disease pathogenesis requires further study. (+info)
Small bowel T cells, HLA class II antigen DR, and GroEL stress protein in IgA nephropathy.
(38/1959)
BACKGROUND: Previous studies suggest that intestinal mucosa may be involved in the pathogenesis of IgA nephropathy (IgAN). To further clarify this involvement, we investigated whether or not IgAN patients have small bowel mucosal findings suggestive of inflammation and stress. METHODS: Seventeen patients with IgAN underwent gastroscopic examination. Fresh small bowel biopsy specimens were frozen, and in cryosections, the proportion of alphabeta and gammadelta receptors bearing T cells and CD3+ T cells were quantitated immunohistochemically. The expression of HLA class II antigen DR (HLA-DR) and human GroEL stress-protein homologue was similarly quantitated. In an avidin-biotin peroxidase technique, the following monoclonal primary antibodies were used: anti-beta-chain (betaF1), anti-delta-chain (TCRdelta1), anti-CD3 (Leu4), anti-constant fragment of HLA-DR (L243), and anti-GroEL (ML30). Twenty-nine patients who had undergone gastroscopy because of dyspepsia served as controls. RESULTS: In all specimens, the mucosal architecture was normal. The amount of gammadelta T cells and the total amount of T cells, as indicated by CD3+ positivity, were both significantly increased in IgAN. The number of alphabeta T cells was also higher in the IgAN patients. Villous epithelium of the IgAN patients disclosed a significant increase in the expression of HLA-DR antigen and GroEL stress protein. CONCLUSIONS: Our results suggest that ongoing small bowel inflammation and stress are present in IgAN. Despite normal morphology, there is reason to believe that the small bowel mucosa is involved in the pathogenesis of IgAN. (+info)
Regulation of NOD mouse autoimmune diabetes by T cells that recognize a TCR CDR3 peptide.
(39/1959)
NOD mice spontaneously develop type I diabetes resulting from autoimmune destruction of their insulin-producing beta cells. Among the self-antigens targeted by NOD autoimmune T cells is a peptide, p277, from the sequence of the 60 kDa heat shock protein (hsp60). Common to the anti-p277 T cell populations of NOD mice is an idiotope, C9, that spans the CDR3 region of the C9 TCR. We now report: (i) that the C9 idiotope peptide can be presented directly to anti-C9 anti-idiotypic T cells by C9 T cells, (ii) that spontaneous anti-C9 anti-idiotypic T cell activity falls as disease progresses, but immunization can activate the anti-idiotypic T cells to regulate the autoimmune process, (iii) that the anti-idiotypic T cells secrete IFN-gamma, but appear to control the disease by down-regulating the IFN-gamma produced by the pathogenic population of anti-p277 T cells, (iv) that intrathymic administration of the C9 idiotope peptide at 1 week of age can accelerate the disease, and (v) that administering the p277 target peptide can up-regulate the anti-idiotypic T cells and arrest the disease process. Thus, the development of NOD diabetes can be regulated by a balance between anti-idiotypic and anti-target peptide autoimmunity, and anti-idiotypic regulation can lead to changes in the cytokine secretion of the autoimmune T cells involved in the disease process. (+info)
Immunohistological analysis of in situ expression of mycobacterial antigens in skin lesions of leprosy patients across the histopathological spectrum. Association of Mycobacterial lipoarabinomannan (LAM) and Mycobacterium leprae phenolic glycolipid-I (PGL-I) with leprosy reactions.
(40/1959)
The presence of mycobacterial antigens in leprosy skin lesions was studied by immunohistological methods using monoclonal antibodies (MAbs) to Mycobacterium leprae-specific phenolic glycolipid I (PGL-I) and to cross-reactive mycobacterial antigens of 36 kd, 65 kd, and lipoarabinomannan (LAM). The staining patterns with MAb to 36 kd and 65 kd were heterogeneous and were also seen in the lesions of other skin diseases. The in situ staining of PGL-I and LAM was seen only in leprosy. Both antigens were abundantly present in infiltrating macrophages in the lesions of untreated multibacillary (MB) patients, whereas only PGL-I was occasionally seen in scattered macrophages in untreated paucibacillary lesions. During treatment, clearance of PGL-I from granulomas in MB lesions occurred before that of LAM, although the former persisted in scattered macrophages in some treated patients. This persistence of PGL-I in the lesions paralleled high serum anti-PGL-I antibody titers but was not indicative for the presence of viable bacilli in the lesions. Interestingly, we also observed a differential expression pattern of PGL-I and LAM in the lesions of MB patients with reactions during the course of the disease as compared with those without reactions. In conclusion, the in situ expression pattern of PGL-I and LAM in MB patients may assist in early diagnosis of reactions versus relapse. (+info)