Dynamic recruitment of phospholipase C gamma at transiently immobilized GPI-anchored receptor clusters induces IP3-Ca2+ signaling: single-molecule tracking study 2

Clusters of CD59, a glycosylphosphatidylinositol-anchored receptor (GPI-AR), with physiological sizes of approximately six CD59 molecules, recruit Galphai2 and Lyn via protein-protein and raft interactions. Lyn is activated probably by the Galphai2 binding in the same CD59 cluster, inducing the CD59 cluster's binding to F-actin, resulting in its immobilization, termed stimulation-induced temporary arrest of lateral diffusion (STALL; with a 0.57-s lifetime, occurring approximately every 2 s). Simultaneous single-molecule tracking of GFP-PLCgamma2 and CD59 clusters revealed that PLCgamma2 molecules are transiently (median = 0.25 s) recruited from the cytoplasm exclusively at the CD59 clusters undergoing STALL, producing the IP(3)-Ca(2+) signal. Therefore, we propose that the CD59 cluster in STALL may be a key, albeit transient, platform for transducing the extracellular GPI-AR signal to the intracellular IP(3)-Ca(2+) signal, via PLCgamma2 recruitment. The prolonged, analogue, bulk IP(3)-Ca(2+) signal, which lasts for more than several minutes, is likely generated by the sum of the short-lived, digital-like IP(3) bursts, each created by the transient recruitment of PLCgamma2 molecules to STALLed CD59.     

Osteopontin aggravates experimental autoimmune uveoretinitis in mice

Human endogenous uveitis is a common sight-threatening intraocular inflammatory disease and has been studied extensively using a murine model of experimental autoimmune uveoretinitis (EAU). It is possibly mediated by Th1 immune responses. In the present study, we investigated the role of osteopontin (OPN), a protein with pleiotropic functions that contributes to the development of Th1 cell-mediated immunity. Accompanying EAU progression, OPN was elevated in wild-type (WT) mice that had been immunized with human interphotoreceptor retinoid-binding protein (hIRBP) peptide 1-20. OPN-deficient (OPN-/-) mice showed milder EAU progression in clinical and histopathological scores compared with those of WT mice. The T cells from hIRBP-immunized OPN-/- mice exhibited reduced Ag-specific proliferation and proinflammatory cytokine (TNF-alpha and IFN-gamma) production compared with those of WT T cells. When hIRBP-immunized WT mice were administered M5 Ab reacting to SLAYGLR sequence, a cryptic binding site to integrins within OPN, EAU development was significantly ameliorated. T cells from hIRBP-immunized WT mice showed significantly reduced proliferative responses and proinflammatory cytokine production upon stimulation with hIRBP peptide in the presence of M5 Ab in the culture. Our present results demonstrate that OPN may represent a novel therapeutic target to control uveoretinitis.     

Do social learning and conformist bias coevolve? Henrich and Boyd revisited

We studied the coevolution of social learning and conformist bias in a modified version of the Henrich and Boyd [1998. The evolution of conformist transmission and the emergence of between-group differences. Evol. Hum. Behav. 19, 215-241] model that nevertheless preserves its essential features. The convergent stable strategies (CSS) are identified by a numerical adaptive dynamics method and then checked for evolutionary stability. A strategy that is simultaneously a CSS and an ESS is called an attractive evolutionarily stable strategy (AESS). Our main findings are as follows. First, the AESS reliance on social learning is monotone increasing in the fixed interval between environmental changes and monotone decreasing in the quality of environmental information. Second, the AESS strength of conformist bias is monotone non-increasing in the fixed interval between environmental changes and monotone non-decreasing in the quality of environmental information. The first observation is in agreement with Henrich and Boyd (1998), but the second is in direct contradiction. In addition, we conducted Monte Carlo simulations as in Henrich and Boyd (1998), which supported our findings. We believe that the reason for the discrepancy with regard to the strength of conformist bias is that Henrich and Boyd (1998) did not allow a sufficient number of iterations for true convergence to occur. In conclusion, the conditions favoring a heavy reliance on social learning are not the same as those favoring a strong conformist bias.     

Mucin-hypersecreting bile duct neoplasm characterized by clinicopathological resemblance to intraductal papillary mucinous neoplasm (IPMN) of the pancreas

Background

Ultrasound-guided vacuum-assisted breast biopsy technology is extremely useful for diagnostic biopsy of suspicious breast lesions and for attempted complete excision of appropriately selected presumed benign breast lesions.

Case presentation

A female patient presented with 16 breast lesions (eight within each breast), documented on ultrasound and all presumed to be fibroadenomas. Over a ten and one-half month period of time, 14 of these 16 breast lesions were removed under ultrasound guidance during a total of 11 separate 8-gauge Mammotome^® excision procedures performed during seven separate sessions. Additionally, two of these 16 breast lesions were removed by open surgical excision. A histopathologic diagnosis of fibroadenoma and/or fibroadenomatous changes was confirmed at all lesion excision sites. Interval follow-up ultrasound imaging revealed no evidence of a residual lesion at the site of any of the 16 original breast lesions.

Conclusion

This report describes an innovative approach of utilizing ultrasound-guided 8-gauge vacuum-assisted breast biopsy technology for assisting in achieving complete eradication of multiple bilateral fibroadenomas in a patient who presented with 16 documented breast lesions. As such, this innovative approach is highly recommended in similar appropriately selected patients.     

Weak interaction induces an ON/OFF switch, whereas strong interaction causes gradual change: folding transition of a long duplex DNA chain by poly-L-lysine

A large-scale conformational change in genomic DNA is an essential feature of gene activation in living cells. Considerable effort has been applied to explain the mechanism in terms of key-lock interaction between sequence-specific regulatory proteins and DNA, in addition to the modification of DNA and histones such as methylation and acetylation. However, it is still unclear whether these mechanisms can explain the ON/OFF switching of a large number of genes that accompanies differentiation, carcinogenesis, etc. In this study, using single-molecule observation of DNA molecules by fluorescence microscopy with the addition of poly-L-lysine with different numbers of monomer units (n = 3, 5, 9, and 92), we found that an ON/OFF discrete transition in the higher-order structure of long duplex DNA is induced by short poly-L-lysine, whereas a continuous gradual change is induced by long poly-L-lysine. On the other hand, polycations with a lower positive charge have less potential to induce DNA compaction. Such a drastic difference in the conformational transition of a giant DNA between short and large oligomers is discussed in relation to the mechanisms of gene regulation in a living cell.     

Studies on Substrate Specificity at PR/p3 Cleavage Site of HTLV-1 Protease

Substrate specificities for recognition at the PR/p3 site of HTLV-1 protease were clarified using small libraries of substrate peptides. Specificities at P₁ and P₁′ positions were examined by parallel synthesis/digestion of synthetic peptides covering the PR/p3 site (KGPPVILPIQA). Specificities at P₂ to P₄ positions were examined by split and mix syntheses of olefin-peptide libraries containing the substrate sequence (PPVILPIQ). The solid-phase Horner-Emmons reaction was successfully applied to syntheses of multi-component substrates for library preparation. From the digestion of substrate peptides by a chemically synthesized mutant of HTLV-1 protease (C2A HTLV-1 PR), it was found for the first time that the preference for Pro at the P₁′ position and for Ile at the P₂ position is unique for this enzyme. We dedicate this article to Prof. Bruce Merrifield for his great role and impact on solid-phase chemistry.     

Metarhizium aciculare sp. nov. for euvesperins A and B producing Metarhizium strains

We have already found some Metarhizium isolates produce euvesperins A and B, which were circumventors of arbekacin resistance in MRSA. These isolates were obtained from soil samples collected from the Izu islands and Kannami town, Sizuoka, Japan. Using a combination of micro-morphological characteristics and multigene (SSU, LSU, TEF) phylogenics, the isolates were identified as a previously underscribed species of Metarhizium. Phylogenetically, the species is close to M. carneum but it is distinguished morphologically from M. carneum by size and the surface structure of conidia.     

Novel Ca2+‐independent carbohydrate recognition of the C‐type lectins,SPL‐1 and SPL‐2, from the bivalve Saxidomus purpuratus

Novel Ca²⁺‐independent C‐type lectins, SPL‐1 and SPL‐2, were purified from the bivalve Saxidomus purpuratus. They are composed of dimers with either identical (SPL‐2 composed of two B‐chains) or distinct (SPL‐1 composed of A‐ and B‐chains) polypeptide chains, and show affinity for N‐acetylglucosamine (GlcNAc)‐ and N‐acetylgalactosamine (GalNAc)‐containing carbohydrates, but not for glucose or galactose. A database search for sequence similarity suggested that they belong to the C‐type lectin family. X‐ray crystallographic analysis revealed definite structural similarities between their subunits and the carbohydrate‐recognition domain (CRD) of the C‐type lectin family. Nevertheless, these lectins (especially SPL‐2) showed Ca²⁺‐independent binding affinity for GlcNAc and GalNAc. The crystal structure of SPL‐2/GalNAc complex revealed that bound GalNAc was mainly recognized via its acetamido group through stacking interactions with Tyr and His residues and hydrogen bonds with Asp and Asn residues, while widely known carbohydrate‐recognition motifs among the C‐type CRD (the QPD [Gln‐Pro‐Asp] and EPN [Glu‐Pro‐Asn] sequences) are not involved in the binding of the carbohydrate. Carbohydrate‐binding specificities of individual A‐ and B‐chains were examined by glycan array analysis using recombinant lectins produced from Escherichia coli cells, where both subunits preferably bound oligosaccharides having terminal GlcNAc or GalNAc with α‐glycosidic linkages with slightly different specificities.     

Recovery of Physiological Traits in Saplings of Invasive Bischofia Tree Compared with Three Species Native to the Bonin Islands under Successive Drought and Irrigation Cycles

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc,) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated drought-irrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands.     

Programmed Cell Death Progresses Differentially in Epidermal and Mesophyll Cells of Lily Petals

In the petals of some species of flowers, programmed cell death (PCD) begins earlier in mesophyll cells than in epidermal cells. However, PCD progression in each cell type has not been characterized in detail. We separately constructed a time course of biochemical signs and expression patterns of PCD-associated genes in epidermal and mesophyll cells in Lilium cv. Yelloween petals. Before visible signs of senescence could be observed, we found signs of PCD, including DNA degradation and decreased protein content in mesophyll cells only. In these cells, the total proteinase activity increased on the day after anthesis. Within 3 days after anthesis, the protein content decreased by 61.8%, and 22.8% of mesophyll cells was lost. A second peak of proteinase activity was observed on day 6, and the number of mesophyll cells decreased again from days 4 to 7. These biochemical and morphological results suggest that PCD progressed in steps during flower life in the mesophyll cells. PCD began in epidermal cells on day 5, in temporal synchrony with the time course of visible senescence. In the mesophyll cells, the KDEL-tailed cysteine proteinase (LoCYP) and S1/P1 nuclease (LoNUC) genes were upregulated before petal wilting, earlier than in epidermal cells. In contrast, relative to that in the mesophyll cells, the expression of the SAG12 cysteine proteinase homolog (LoSAG12) drastically increased in epidermal cells in the final stage of senescence. These results suggest that multiple PCD-associated genes differentially contribute to the time lag of PCD progression between epidermal and mesophyll cells of lily petals.