Two subtypes of HLA-B51 differing by substitution at position 171 of the α2 helix

Newly defined antigens of the B5, B35 cross-reacting group have been found in Japanese and North American Indians. Nucleotide sequencing of the alleles encoding the Japanese B5.35 antigen and the variant B5 antigen from the Piman Indians show them to be identical. This new allele, B ^* 5102, differs from B ^* 5101 by a single nucleotide substitution that changes residue 171 from histidine to tyrosine. Residue 171, which is part of the ₂ helix, is believed to contribute directly to peptide interaction in the A pocket of the binding groove and is either histidine or tyrosine in all HLA-A, B, C heavy chains. Tyrosine 171 is shared by B ^* 5102, B ^* 3501, B ^* 3502, and B ^* 5301 and must be responsible for the serological cross-reactivities of these molecules not shared with B ^* 5101. Stimulation of lymphocytes from a B ^* 5101 positive donor with B ^* 5102 positive cells failed to generate cytotoxic T cells with specificity for the difference between these molecules. However, one out of five clones of cytotoxic T cells raised against B ^* 5101 failed to lyse targets expressing B ^* 5102. Substitution of histidine for tyrosine at residue 171 affected recognition of HLA-B35-restricted human minor histocompatibility antigen-specific T cell clones.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number M68964.     

<Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>-purpura fulminans as an invasive form of group A streptococcal infection

Background

Streptococcus pyogenes is an uncommon pathogen of purpura fulminans, and the pathogenesis of S. pyogenes-purpura fulminans remains unclear because of paucity of cases. We reported a pediatric case of S. pyogenes-purpura fulminans with literature review of the disease.

Case presentation

A 3-year-old boy showed limping, lethargy and acral gangrene within 24 h. A diagnosis of S. pyogenes-purpura fulminans was made for bacterial isolation from throat and peripheral blood. Intensive therapy led to a survival with amputation of the left distal metatarsal bone, and normal development. The isolated M12 carried no mutation of csrS/R or rgg. Thrombophilia or immunodeficiency was excluded.

Discussion

Twelve-reported cases (9 pediatric and 3 elderly) of S. pyogenes-purpura fulminans started with shock and coagulopathy. Five patients age <?8 years had no underlying disease and survived. One youngest and two immunocompromised patients died.

Conclusion

Streptococcus pyogenes-acute infectious purpura fulminans is a distinctive rare form of aggressive GAS infections.

     

Intramolecular excitation energy transfer in diarylurea-linked zinc porphyrin-anthracene dyads.

Structurally controlled zinc porphyrin-anthracene dyads, syn-arranged 1 and anti-arranged 2, were newly synthesized employing a diarylurea linkage, and the excitation energy transfer (EET) from the anthracene to the zinc porphyrin chromophore was investigated by steady-state fluorescence emission spectroscopy as well as fluorescence lifetime measurement, especially focusing on the effect of the chromophoric orientation on the EET. In both of the dyads, intramolecular EET was facilitated upon excitation of the anthracene chromophore (lamda(ex)= 401 nm), and the zinc porphyrin S1-S0 emission (580-720 nm) was enhanced. The EET in the syn-arranged dyad 1 was more efficient than in the anti-arranged 2: the S1-S0 emission in 1 was 1.8 times larger than that in the zinc porphyrin reference compound 3, whereas that in 2 was enhanced by 1.6 times, compared to that in 3. In the fluorescence lifetime measurement, the quiet short-lived component assignable to the EET was observed for the dyads 1 and 2 beyond the analysis limit (<25 ps). The EET rate constants in the dyads 1 and 2 were estimated as not less than 4.0 x 10(10) s-1. However, in the case of 2, the residual long-lived component assigned to the anthracene emission was also observed at 425 nm. These results showed that the syn-arrangement of the zinc porphyrin and anthracene chromophores was more preferred for intramolecular EET to the anti-arrangement.     

Inverse relationship between poly (ADP-ribose) polymerase activity and 2′,5′-oligoadenylates core level in estrogen-treated immature rat

Summary The activity of poly (ADP-ribose) polymerase (ADPRP) and the content of 2,5-oligodenylates core (2,5A_n; n = 2,3 and 4) were measured in homogenates of the uterus and of the liver of immature rats immediately before (time 0) or at different times after injection of estradiol-valerate. ADPRP activity increased gradualy, starting 6 hours after estrogen injection, for about 4 days. Instead, the content of 2,5 A_n decreased by about 50% within 6 hours, and thereafter more slowly for 4 days to about 20% of starting values. Estrogen increased ADPRP activity and decreased 2,5A_n concentration also in the kidney and in the cardiac muscle of the same animals, but not in the skeletal muscle, where neither of the two parameters was affected. Injection of vehicle only (sesame oil) had no effect on ADPRP activity nor on 2,5A_n content of immature rat tissues.     

Proximate stimuli: An overlooked driving force for risk-induced trait responses affecting interactions in aquatic ecosystems

Inducible responses in prey to predation risk can influence species interaction strength, with significant ecological consequences. Much of the past research on interactions in aquatic ecosystems has focused on remote stimuli (e.g., diffusible chemicals emitted from predators and injured conspecifics, which easily propagate through environmental water), as cues triggering trait responses in prey, and has overlooked the importance of proximate stimuli (e.g., physical disturbance and less-diffusible chemicals), which occur in attack or direct contact to prey by predators. Proximate stimuli from predators as well as remote stimuli may induce significant responses in prey functional traits such as behavior, morphology, and life history and, therefore, act as an important mechanism of top-down effects in aquatic ecosystems. In this opinion paper, we argue that studying the effects of proximate stimuli is essential to better understanding of individual adaptation to predation risk in nature and ecological consequences of predator–prey interactions. Here, we propose research directions to examine the role of proximate stimuli for phenotypic plasticity and interaction systems.     

A new class of pentapeptide KISS1 receptor agonists with hypothalamic–pituitary–gonadal axis activation

The kisspeptin (Kp, Kp-54, metastin)/KISS1R system plays crucial roles in regulating the secretion of gonadotropin-releasing hormone. Continuous administration of nonapeptide Kp analogs caused plasma testosterone depletion, whereas bolus administration caused strong plasma testosterone elevation in male rats. To develop a new class of small peptide drugs, we focused on stepwise N-terminal truncation of Kp analogs and discovered potent pentapeptide analogs. Benzoyl-Phe-azaGly-Leu-Arg(Me)-Trp-NH₂ (16) exhibited high agonist activity for KISS1R and excellent metabolic stability in rat serum. A single injection of a 4-pyridyl analog (19) at the N-terminus of 16 into male Sprague Dawley rats caused a robust increase in plasma luteinizing hormone levels, but unlike continuous administration of nonapeptide Kp analogs, continuous administration of 19 maintained moderate testosterone levels in rats. These results indicated that small peptide drugs can be successfully developed for treating sex hormone deficiency.     

Regulation of Autophagy and Its Associated Cell Death by “Sphingolipid Rheostat”: RECIPROCAL ROLE OF CERAMIDE AND SPHINGOSINE 1-PHOSPHATE IN THE MAMMALIAN TARGET OF RAPAMYCIN PATHWAY*

The role of “sphingolipid rheostat” by ceramide and sphingosine 1-phosphate (S1P) in the regulation of autophagy remains unclear. In human leukemia HL-60 cells, amino acid deprivation (AA(−)) caused autophagy with an increase in acid sphingomyleinase (SMase) activity and ceramide, which serves as an autophagy inducing lipid. Knockdown of acid SMase significantly suppressed the autophagy induction. S1P treatment counteracted autophagy induction by AA(−) or C₂-ceramide. AA(−) treatment promoted mammalian target of rapamycin (mTOR) dephosphorylation/inactivation, inducing autophagy. S1P treatment suppressed mTOR inactivation and autophagy induction by AA(−). S1P exerts biological actions via cell surface receptors, and S1P₃ among five S1P receptors was predominantly expressed in HL-60 cells. We evaluated the involvement of S1P₃ in suppressing autophagy induction. S1P treatment of CHO cells had no effects on mTOR inactivation and autophagy induction by AA(−) or C₂-ceramide. Whereas S1P treatment of S1P₃ overexpressing CHO cells resulted in activation of the mTOR pathway, preventing cells from undergoing autophagy induced by AA(−) or C₂-ceramide. These results indicate that S1P-S1P₃ plays a role in counteracting ceramide signals that mediate mTOR-controlled autophagy. In addition, we evaluated the involvement of ceramide-activated protein phosphatases (CAPPs) in ceramide-dependent inactivation of the mTOR pathway. Inhibition of CAPP by okadaic acid in AA(−)- or C₂-ceramide-treated cells suppressed dephosphorylation/inactivation of mTOR, autophagy induction, and autophagy-associated cell death, indicating a novel role of ceramide-CAPPs in autophagy induction. Moreover, S1P₃ engagement by S1P counteracted cell death. Taken together, these results indicated that sphingolipid rheostat in ceramide-CAPPs and S1P-S1P₃ signaling modulates autophagy and its associated cell death through regulation of the mTOR pathway.     

Munc13-4 reconstitutes calcium-dependent SNARE-mediated membrane fusion

Munc13-4 is a widely expressed member of the CAPS/Munc13 protein family proposed to function in priming secretory granules for exocytosis. Munc13-4 contains N- and C-terminal C2 domains (C2A and C2B) predicted to bind Ca(2+), but Ca(2+)-dependent regulation of Munc13-4 activity has not been described. The C2 domains bracket a predicted SNARE-binding domain, but whether Munc13-4 interacts with SNARE proteins is unknown. We report that Munc13-4 bound Ca(2+) and restored Ca(2+)-dependent granule exocytosis to permeable cells (platelets, mast, and neuroendocrine cells) dependent on putative Ca(2+)-binding residues in C2A and C2B. Munc13-4 exhibited Ca(2+)-stimulated SNARE interactions dependent on C2A and Ca(2+)-dependent membrane binding dependent on C2B. In an apparent coupling of membrane and SNARE binding, Munc13-4 stimulated SNARE-dependent liposome fusion dependent on putative Ca(2+)-binding residues in both C2A and C2B domains. Munc13-4 is the first priming factor shown to promote Ca(2+)-dependent SNARE complex formation and SNARE-mediated liposome fusion. These properties of Munc13-4 suggest its function as a Ca(2+) sensor at rate-limiting priming steps in granule exocytosis.     

Regulatory mechanism for the stimulatory action of genistein on glucose uptake in vitro and in vivo

Genistein, an isoflavone, is known to possess diverse biological functions such as antioxidative and anti-inflammatory actions. It also acts like estrogen and inhibits several tyrosine kinases. Genistein was reported to suppress insulin-mediated glucose uptake in adipocytes. In this study, we investigated the effects of genistein on glucose uptake in vitro and in vivo as well as the mechanisms associated with the glucose uptake. We found that genistein decreased nonfasting blood glucose levels in KK-Ay/Ta Jcl mice, a type 2 diabetic animal model. It also dose-dependently induced insulin secretion by Rin-5F cells. In L6 myotubes, it directly stimulated glucose uptake independently of insulin under normal and high glucose conditions in dose-dependent manners. It promoted the translocation of glucose transporter 4 to the cell membrane under both glucose conditions. Based on studies using inhibitors of signaling molecules related to glucose uptake, the stimulatory effect of genistein on glucose uptake appeared to be dependent on the phosphatidylinositol 3-kinase, mammalian target of rapamycin, protein kinase C and 5'-adenosine-monophosphate-activated protein kinase pathway under both glucose conditions. In addition, O-GlcNAcylation by O-(2-acetamido-2-deoxy-D-glucopyranosylidene) amino N-phenyl carbamate, an inhibitor of N-acetylglucosaminidase, reduced the stimulatory effect of genistein on glucose uptake under both glucose conditions. Taken together, genistein may regulate glucose uptake by increasing the phosphorylation and decreasing the O-GlcNAcylation of proteins related to glucose homeostasis.