The precise restriction of proteins to specific domains within a cell plays an important role in ... more The precise restriction of proteins to specific domains within a cell plays an important role in early development and differentiation. An efficient way to localize and concentrate proteins is by localization of mRNA in a translationally repressed state, followed by activation of translation when the mRNA reaches its destination. A central issue is how localized mRNAs are derepressed. In this study we demonstrate that, when oskar mRNA reaches the posterior pole of the Drosophila oocyte, its translation is derepressed by an active process that requires a specific element in the 5 region of the mRNA. We demonstrate that this novel type of element is a translational derepressor element, whose functional interaction with the previously identified repressor region in the oskar 3 UTR is required for activation of oskar mRNA translation at the posterior pole. The derepressor element only functions at the posterior pole, suggesting that a locally restricted interaction between trans-acting factors and the derepressor element may be the link between mRNA localization and translational activation. We also show specific interaction of two proteins with the oskar mRNA 5 region; one of these also recognizes the 3 repressor element. We discuss the possible involvement of these factors as well as known genes in the process of localization-dependent translation.
Reactive oxygen species (ROS) often injure intestinal epithelia that cause loss of damaged cells,... more Reactive oxygen species (ROS) often injure intestinal epithelia that cause loss of damaged cells, which is mainly repaired by proliferation of intestinal stem cells (ISCs). To maintain the homeostatic state, coordination of sensing of the ROS injury and the subsequent epithelial cell loss with the replenishment by cell renewal is crucial. However, little is known about how gut epithelial cells initiate regenerative responses against ROS to maintain the tissue integrity. Here, we carried out a genome‐wide screen, by which we identify immunoglobulin superfamily beaten path Ib (beat‐Ib) as an essential gene for provoking ISC proliferation against ROS in Drosophila intestine. Interestingly, the beat‐Ib function is required in differentiated enterocytes, the main targeted cells by ROS in the intestinal tract, but is dispensable in the stem cells. Moreover, beat‐Ib is not involved in enterocyte apoptosis at ROS injury. These findings indicate the essential role of beat‐Ib in Drosophila mi...
Innate immunity is an evolutionarily conserved host defense system against infections. The fruit ... more Innate immunity is an evolutionarily conserved host defense system against infections. The fruit fly Drosophila relies solely on innate immunity for infection defense, and the conservation of innate immunity makes Drosophila an ideal model for understanding the principles of innate immunity, which comprises both humoral and cellular responses. The mechanisms underlying the coordination of humoral and cellular responses, however, has remained unclear. Previously, we identified Gyc76C, a receptor-type guanylate cyclase that produces cyclic guanosine monophosphate (cGMP), as an immune receptor in Drosophila. Gyc76C mediates the induction of antimicrobial peptides for humoral responses by a novel cGMP pathway including a membrane-localized cGMP-dependent protein kinase, DG2, through downstream components of the Toll receptor such as dMyD88. Here we show that Gyc76C is also required for the proliferation of blood cells (hemocytes) for cellular responses to bacterial infections. In contrast to Gyc76C-dependent antimicrobial peptide induction, Gyc76C-dependent hemocyte proliferation is meditated by a small GTPase, Ras85D, and not by DG2 or dMyD88, indicating that Gyc76C mediates the cellular and humoral immune responses in distinct ways.
A temperature-sensitive mutant defective in DNA replication, tsFT848, was isolated from the mouse... more A temperature-sensitive mutant defective in DNA replication, tsFT848, was isolated from the mouse mammary carcinoma cell line FM3A. In mutant cells, the DNA-dependent ATPase activity of DNA helicase B, which is a major DNA-dependent ATPase in wild-type cells, decreased at the nonpermissive temperature of 39 degrees C. DNA synthesis in tsFT848 cells at the nonpermissive temperature was analyzed in detail. DNA synthesis measured by incorporation of [3H]thymidine decreased to about 50% and less than 10% of the initial level at 8 and 12 h, respectively. The decrease in the level of thymidine incorporation correlated with a decrease in the number of silver grains in individual nuclei but not with the number of cells with labeled nuclei. DNA fiber autoradiography revealed that the DNA chain elongation rate did not decrease even after an incubation for 10 h at 39 degrees C, suggesting that initiation of DNA replication at the origen of replicons is impaired in the mutant cells. The decreas...
Genes to cells : devoted to molecular & cellular mechanisms, 2016
Over-expression of Winged-Eye (WGE) in the Drosophila eye imaginal disc induces an eye-to-wing tr... more Over-expression of Winged-Eye (WGE) in the Drosophila eye imaginal disc induces an eye-to-wing transformation. Endogenous WGE is required for organ development, and wge-deficient mutants exhibit growth arrest at the larval stage, suggesting that WGE is critical for normal growth. The function of WGE, however, remains unclear. Here, we analyzed the subcellular localization of WGE to gain insight into its endogenous function. Immunostaining showed that WGE localized to specific nuclear foci called the histone locus body (HLB), an evolutionarily conserved nuclear body required for S phase-specific histone mRNA production. Histone mRNA levels and protein levels in cytosolic fractions were aberrantly up-regulated in wge mutant larva, suggesting a role for WGE in regulating histone gene expression. Genetic analyses showed that wge suppresses position-effect variegation, and that WGE and a HLB component Mute appears to be synergistically involved in heterochromatin formation. Further suppo...
Proceedings of the National Academy of Sciences of the United States of America, Jan 15, 2002
In Drosophila, microbial infection activates an antimicrobial defense system involving the activa... more In Drosophila, microbial infection activates an antimicrobial defense system involving the activation of proteolytic cascades in the hemolymph and intracellular signaling pathways, the immune deficiency (imd) and Toll pathways, in immune-responsive tissues. The mechanisms for microbial recognition are largely unknown. We report that, in larvae, the imd-mediated antibacterial defense is activated by peptidoglycan-recognition protein (PGRP)-LE, a PGRP-family member in Drosophila. Consistent with this, PGRP-LE binds to the diaminopimelic acid-type peptidoglycan, a cell-wall component of the bacteria capable of activating the imd pathway, but not to the lysine-type peptidoglycan. Moreover, PGRP-LE activates the prophenoloxidase cascade, a proteolytic cascade in the hemolymph. Therefore, PGRP-LE acts as a pattern-recognition receptor to the diaminopimelic acid-type peptidoglycan and activates both the proteolytic cascade and intracellular signaling in Drosophila immunity.
Previously, we reported that cathepsin B of pupal hemocytes participates in dissociation of the f... more Previously, we reported that cathepsin B of pupal hemocytes participates in dissociation of the fat body of Sarcophaga larvae at metamorphosis. In this study, we demonstrated that the amount of cathepsin B in hemocytes was controlled at the translational level, i.e. larval hemocytes stored a significant amount of untranslated cathepsin B mRNA. When the larvae pupated, translation of the mRNA commenced, resulting in accumulation of cathepsin B. Our results indicate that the 3'-untranslated region (3'-UTR) of this mRNA is necessary for the repression of its translation in a rabbit reticulocyte lysate. We detected the 3'-UTR binding protein in the lysate of larval hemocytes, but not in the pupal hemocytes. The role of this protein in the translation of cathepsin B mRNA is discussed.
In innate immunity, pattern recognition molecules recognize cell wall components of microorganism... more In innate immunity, pattern recognition molecules recognize cell wall components of microorganisms and activate subsequent immune responses, such as the induction of antimicrobial peptides and melanization in Drosophila. The diaminopimelic acid (DAP)-type peptidoglycan potently activates imd-dependent induction of antibacterial peptides. Peptidoglycan recognition protein (PGRP) family members act as pattern recognition molecules. PGRP-LC loss-of-function mutations affect the imd-dependent induction of antibacterial peptides and resistance to Gramnegative bacteria, whereas PGRP-LE binds to the DAPtype peptidoglycan, and a gain-of-function mutation induces constitutive activation of both the imd pathway and melanization. Here, we generated PGRP-LE null mutants and report that PGRP-LE functions synergistically with PGRP-LC in producing resistance to Escherichia coli and Bacillus megaterium infections, which have the DAP-type peptidoglycan. Consistent with this, PGRP-LE acts both upstream and in parallel with PGRP-LC in the imd pathway, and is required for infection-dependent activation of melanization in Drosophila. A role for PGRP-LE in the epithelial induction of antimicrobial peptides is also suggested.
Autophagy has been linked to inflammatory bowel disease. Studies of two different mouse strains d... more Autophagy has been linked to inflammatory bowel disease. Studies of two different mouse strains deficient in the autophagy-related gene product Atg16L1 now show that autophagy is important in regulating the secretory function of Paneth cells and the production of inflammatory cytokines in the intestine.
Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components... more Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components, has been linked to the elimination of intracellular pathogens during mammalian innate immune responses. However, the mechanisms underlying cytoplasmic infection-induced autophagy and the function of autophagy in host survival after infection with intracellular pathogens remain unknown. Here we report that in drosophila, recognition of diaminopimelic acid-type peptidoglycan by the pattern-recognition receptor PGRP-LE was crucial for the induction of autophagy and that autophagy prevented the intracellular growth of Listeria monocytogenes and promoted host survival after this infection. Autophagy induction occurred independently of the Toll and IMD innate signaling pathways. Our findings define a pathway leading from the intracellular pattern-recognition receptors to the induction of autophagy to host defense.
Intracellular bacteria cause serious infectious diseases such as tuberculosis, shigellosis, and l... more Intracellular bacteria cause serious infectious diseases such as tuberculosis, shigellosis, and listeriosis. The Drosophila peptidoglycan recognition protein (PGRP)-LE functions as an important host pattern recognition receptor against intracellular bacteria such as Listeria monocytogenes. One PGRP-LE-mediated intracellular response against L. monocytogenes infection is the induction of autophagy, a conserved intracellular degradation system. Here, to further elucidate PGRP-LE-mediated intracellular innate immune responses, we performed a strategic microarray analysis and identified the Listericin gene, whose expression is induced in response to L. monocytogenes infection in a PGRP-LE-dependent manner. RNA interference and overexpression experiments demonstrated that Listericin gene induction is cooperatively regulated by PGRP-LE and the JAK-STAT (Janus kinase-signal transducers and activators of transcription) pathway. An in vitro cell culture assay showed that Listericin is secreted as processed forms and suppresses the growth of L. monocytogenes and Gram-negative bacteria. A colony formation unit assay clearly demonstrated that induction of the Listericin gene suppresses not only the growth of L. monocytogenes but also the growth of Gram-negative bacteria in vivo. Based on these findings, we propose that the Listericin gene encodes a novel antibacterial peptide-like protein whose induction is cooperatively regulated by PGRP-LE and the JAK-STAT pathway.
Drosophila peptidoglycan recognition protein (PGRP)-LCx and -LCa are receptors that preferentiall... more Drosophila peptidoglycan recognition protein (PGRP)-LCx and -LCa are receptors that preferentially recognize meso-diaminopimelic acid (DAP)-type peptidoglycan (PGN) present in Gram-negative bacteria over lysine-type PGN of Gram-positive bacteria and initiate the IMD signaling pathway, whereas PGRP-LE plays a synergistic role in this process of innate immune defense. How these receptors can distinguish the two types of PGN remains unclear. Here the structure of the PGRP domain of Drosophila PGRP-LE in complex with tracheal cytotoxin (TCT), the monomeric DAP-type PGN, reveals a buried ionic interaction between the unique carboxyl group of DAP and a previously unrecognized arginine residue. This arginine is conserved in the known DAP-type PGN-interacting PGRPs and contributes significantly to the affinity of the protein for the ligand. Unexpectedly, TCT induces infinite head-to-tail dimerization of PGRP-LE, in which the disaccharide moiety, but not the peptide stem, of TCT is positioned at the dimer interface. A sequence comparison suggests that TCT induces heterodimerization of the ectodomains of PGRP-LCx and -LCa in a closely analogous manner to prime the IMD signaling pathway, except that the heterodimer formation is nonperpetuating. Innate immune defenses against pathogens are initiated by pattern recognition receptors that bind conserved stereotypical, rather than particular, molecular structures present in a wide spectrum of microorganisms but absent in the host (1). A representative example of such structures is peptidoglycan (PGN), 3 the major constituent of the cell wall of both Gram-positive and -negative bacteria. The peptidoglycan recognition protein (PGRP) family is a class of pattern recognition receptors that bind, and sometimes cleave, PGN. A total of 13 and four PGRP family members have been identified in Drosophila and humans, respectively (2-5). PGRPs are often characterized based on their * This work was supported by Creative Research Initiatives of the Korean Ministry of Science and Technology. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The atomic coordinates and structure factors (code 2CB3) have been deposited in the Protein Data Bank,
Pathogen recognition is the first and crucial step in innate immunity. Molecular families involve... more Pathogen recognition is the first and crucial step in innate immunity. Molecular families involved in the recognition of pathogens and activation of the innate immune responses in immunoreactive cells include the Toll-like receptor family in mammals and the peptidoglycan recognition protein (PGRP) family in Drosophila, which sense microorganisms in an extracellular or luminal compartment. Other emerging families are the intracellular recognition molecules for bacteria, such as nucleotide binding and oligomerization domain-like receptors in mammals and PGRPLE in Drosophila, several of which have been shown to detect structures of bacterial peptidoglycan in the host cell cytosol. Exciting advances in recent studies on autophagy indicate that macroautophagy (referred to here as autophagy) is selectively induced by intracellular recognition molecules and has a crucial role in the elimination of intracellular pathogens, including bacteria, viruses and parasites. This review discusses recent studies related to intracellular recognition molecules and innate immune responses to intracellular pathogens, and highlights the role of autophagy in innate immunity.
The modori phenomenon during surimi production is caused by endogenous proteinases, especially ca... more The modori phenomenon during surimi production is caused by endogenous proteinases, especially cathepsin L and myofibril-bound serine proteinase (MBSP). Cathepsin L from the skeletal muscle of blue scad (Decapterus maruadsi) was purified to homogeneity by ammonium sulphate fractionation and a series of column chromatographies and revealed a single band with molecular mass of 30 kDa on SDS-PAGE. Peptide mass fingerprinting (PMF) obtained three fragments with 48 amino acid residues, which were highly identical to cathepsin L from other fish species. Its optimal pH and temperature were 5.5 and 55 °C, respectively. Meanwhile, MBSP was purified from the skeletal muscle of blue scad, and the roles of cathepsin L and MBSP in the degradation of myofibrillar proteins were compared. The results indicated that MBSP is more effective than cathepsin L in promoting the degradation of myofibrillar proteins, especially myosin heavy chain (MHC), suggesting that MBSP plays a more significant role.
Hrp48, a Drosophila hnRNPA/B Homolog, Binds and Regulates Translation of oskar mRNA germline dete... more Hrp48, a Drosophila hnRNPA/B Homolog, Binds and Regulates Translation of oskar mRNA germline determinants. oskar is both necessary and sufficient for pole plasm formation (Ephrussi and Lehmann, 1992; Lehmann and Nu ¨sslein-Volhard, 1986). oskar mu-
The precise restriction of proteins to specific domains within a cell plays an important role in ... more The precise restriction of proteins to specific domains within a cell plays an important role in early development and differentiation. An efficient way to localize and concentrate proteins is by localization of mRNA in a translationally repressed state, followed by activation of translation when the mRNA reaches its destination. A central issue is how localized mRNAs are derepressed. In this study we demonstrate that, when oskar mRNA reaches the posterior pole of the Drosophila oocyte, its translation is derepressed by an active process that requires a specific element in the 5 region of the mRNA. We demonstrate that this novel type of element is a translational derepressor element, whose functional interaction with the previously identified repressor region in the oskar 3 UTR is required for activation of oskar mRNA translation at the posterior pole. The derepressor element only functions at the posterior pole, suggesting that a locally restricted interaction between trans-acting factors and the derepressor element may be the link between mRNA localization and translational activation. We also show specific interaction of two proteins with the oskar mRNA 5 region; one of these also recognizes the 3 repressor element. We discuss the possible involvement of these factors as well as known genes in the process of localization-dependent translation.
Reactive oxygen species (ROS) often injure intestinal epithelia that cause loss of damaged cells,... more Reactive oxygen species (ROS) often injure intestinal epithelia that cause loss of damaged cells, which is mainly repaired by proliferation of intestinal stem cells (ISCs). To maintain the homeostatic state, coordination of sensing of the ROS injury and the subsequent epithelial cell loss with the replenishment by cell renewal is crucial. However, little is known about how gut epithelial cells initiate regenerative responses against ROS to maintain the tissue integrity. Here, we carried out a genome‐wide screen, by which we identify immunoglobulin superfamily beaten path Ib (beat‐Ib) as an essential gene for provoking ISC proliferation against ROS in Drosophila intestine. Interestingly, the beat‐Ib function is required in differentiated enterocytes, the main targeted cells by ROS in the intestinal tract, but is dispensable in the stem cells. Moreover, beat‐Ib is not involved in enterocyte apoptosis at ROS injury. These findings indicate the essential role of beat‐Ib in Drosophila mi...
Innate immunity is an evolutionarily conserved host defense system against infections. The fruit ... more Innate immunity is an evolutionarily conserved host defense system against infections. The fruit fly Drosophila relies solely on innate immunity for infection defense, and the conservation of innate immunity makes Drosophila an ideal model for understanding the principles of innate immunity, which comprises both humoral and cellular responses. The mechanisms underlying the coordination of humoral and cellular responses, however, has remained unclear. Previously, we identified Gyc76C, a receptor-type guanylate cyclase that produces cyclic guanosine monophosphate (cGMP), as an immune receptor in Drosophila. Gyc76C mediates the induction of antimicrobial peptides for humoral responses by a novel cGMP pathway including a membrane-localized cGMP-dependent protein kinase, DG2, through downstream components of the Toll receptor such as dMyD88. Here we show that Gyc76C is also required for the proliferation of blood cells (hemocytes) for cellular responses to bacterial infections. In contrast to Gyc76C-dependent antimicrobial peptide induction, Gyc76C-dependent hemocyte proliferation is meditated by a small GTPase, Ras85D, and not by DG2 or dMyD88, indicating that Gyc76C mediates the cellular and humoral immune responses in distinct ways.
A temperature-sensitive mutant defective in DNA replication, tsFT848, was isolated from the mouse... more A temperature-sensitive mutant defective in DNA replication, tsFT848, was isolated from the mouse mammary carcinoma cell line FM3A. In mutant cells, the DNA-dependent ATPase activity of DNA helicase B, which is a major DNA-dependent ATPase in wild-type cells, decreased at the nonpermissive temperature of 39 degrees C. DNA synthesis in tsFT848 cells at the nonpermissive temperature was analyzed in detail. DNA synthesis measured by incorporation of [3H]thymidine decreased to about 50% and less than 10% of the initial level at 8 and 12 h, respectively. The decrease in the level of thymidine incorporation correlated with a decrease in the number of silver grains in individual nuclei but not with the number of cells with labeled nuclei. DNA fiber autoradiography revealed that the DNA chain elongation rate did not decrease even after an incubation for 10 h at 39 degrees C, suggesting that initiation of DNA replication at the origen of replicons is impaired in the mutant cells. The decreas...
Genes to cells : devoted to molecular & cellular mechanisms, 2016
Over-expression of Winged-Eye (WGE) in the Drosophila eye imaginal disc induces an eye-to-wing tr... more Over-expression of Winged-Eye (WGE) in the Drosophila eye imaginal disc induces an eye-to-wing transformation. Endogenous WGE is required for organ development, and wge-deficient mutants exhibit growth arrest at the larval stage, suggesting that WGE is critical for normal growth. The function of WGE, however, remains unclear. Here, we analyzed the subcellular localization of WGE to gain insight into its endogenous function. Immunostaining showed that WGE localized to specific nuclear foci called the histone locus body (HLB), an evolutionarily conserved nuclear body required for S phase-specific histone mRNA production. Histone mRNA levels and protein levels in cytosolic fractions were aberrantly up-regulated in wge mutant larva, suggesting a role for WGE in regulating histone gene expression. Genetic analyses showed that wge suppresses position-effect variegation, and that WGE and a HLB component Mute appears to be synergistically involved in heterochromatin formation. Further suppo...
Proceedings of the National Academy of Sciences of the United States of America, Jan 15, 2002
In Drosophila, microbial infection activates an antimicrobial defense system involving the activa... more In Drosophila, microbial infection activates an antimicrobial defense system involving the activation of proteolytic cascades in the hemolymph and intracellular signaling pathways, the immune deficiency (imd) and Toll pathways, in immune-responsive tissues. The mechanisms for microbial recognition are largely unknown. We report that, in larvae, the imd-mediated antibacterial defense is activated by peptidoglycan-recognition protein (PGRP)-LE, a PGRP-family member in Drosophila. Consistent with this, PGRP-LE binds to the diaminopimelic acid-type peptidoglycan, a cell-wall component of the bacteria capable of activating the imd pathway, but not to the lysine-type peptidoglycan. Moreover, PGRP-LE activates the prophenoloxidase cascade, a proteolytic cascade in the hemolymph. Therefore, PGRP-LE acts as a pattern-recognition receptor to the diaminopimelic acid-type peptidoglycan and activates both the proteolytic cascade and intracellular signaling in Drosophila immunity.
Previously, we reported that cathepsin B of pupal hemocytes participates in dissociation of the f... more Previously, we reported that cathepsin B of pupal hemocytes participates in dissociation of the fat body of Sarcophaga larvae at metamorphosis. In this study, we demonstrated that the amount of cathepsin B in hemocytes was controlled at the translational level, i.e. larval hemocytes stored a significant amount of untranslated cathepsin B mRNA. When the larvae pupated, translation of the mRNA commenced, resulting in accumulation of cathepsin B. Our results indicate that the 3'-untranslated region (3'-UTR) of this mRNA is necessary for the repression of its translation in a rabbit reticulocyte lysate. We detected the 3'-UTR binding protein in the lysate of larval hemocytes, but not in the pupal hemocytes. The role of this protein in the translation of cathepsin B mRNA is discussed.
In innate immunity, pattern recognition molecules recognize cell wall components of microorganism... more In innate immunity, pattern recognition molecules recognize cell wall components of microorganisms and activate subsequent immune responses, such as the induction of antimicrobial peptides and melanization in Drosophila. The diaminopimelic acid (DAP)-type peptidoglycan potently activates imd-dependent induction of antibacterial peptides. Peptidoglycan recognition protein (PGRP) family members act as pattern recognition molecules. PGRP-LC loss-of-function mutations affect the imd-dependent induction of antibacterial peptides and resistance to Gramnegative bacteria, whereas PGRP-LE binds to the DAPtype peptidoglycan, and a gain-of-function mutation induces constitutive activation of both the imd pathway and melanization. Here, we generated PGRP-LE null mutants and report that PGRP-LE functions synergistically with PGRP-LC in producing resistance to Escherichia coli and Bacillus megaterium infections, which have the DAP-type peptidoglycan. Consistent with this, PGRP-LE acts both upstream and in parallel with PGRP-LC in the imd pathway, and is required for infection-dependent activation of melanization in Drosophila. A role for PGRP-LE in the epithelial induction of antimicrobial peptides is also suggested.
Autophagy has been linked to inflammatory bowel disease. Studies of two different mouse strains d... more Autophagy has been linked to inflammatory bowel disease. Studies of two different mouse strains deficient in the autophagy-related gene product Atg16L1 now show that autophagy is important in regulating the secretory function of Paneth cells and the production of inflammatory cytokines in the intestine.
Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components... more Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components, has been linked to the elimination of intracellular pathogens during mammalian innate immune responses. However, the mechanisms underlying cytoplasmic infection-induced autophagy and the function of autophagy in host survival after infection with intracellular pathogens remain unknown. Here we report that in drosophila, recognition of diaminopimelic acid-type peptidoglycan by the pattern-recognition receptor PGRP-LE was crucial for the induction of autophagy and that autophagy prevented the intracellular growth of Listeria monocytogenes and promoted host survival after this infection. Autophagy induction occurred independently of the Toll and IMD innate signaling pathways. Our findings define a pathway leading from the intracellular pattern-recognition receptors to the induction of autophagy to host defense.
Intracellular bacteria cause serious infectious diseases such as tuberculosis, shigellosis, and l... more Intracellular bacteria cause serious infectious diseases such as tuberculosis, shigellosis, and listeriosis. The Drosophila peptidoglycan recognition protein (PGRP)-LE functions as an important host pattern recognition receptor against intracellular bacteria such as Listeria monocytogenes. One PGRP-LE-mediated intracellular response against L. monocytogenes infection is the induction of autophagy, a conserved intracellular degradation system. Here, to further elucidate PGRP-LE-mediated intracellular innate immune responses, we performed a strategic microarray analysis and identified the Listericin gene, whose expression is induced in response to L. monocytogenes infection in a PGRP-LE-dependent manner. RNA interference and overexpression experiments demonstrated that Listericin gene induction is cooperatively regulated by PGRP-LE and the JAK-STAT (Janus kinase-signal transducers and activators of transcription) pathway. An in vitro cell culture assay showed that Listericin is secreted as processed forms and suppresses the growth of L. monocytogenes and Gram-negative bacteria. A colony formation unit assay clearly demonstrated that induction of the Listericin gene suppresses not only the growth of L. monocytogenes but also the growth of Gram-negative bacteria in vivo. Based on these findings, we propose that the Listericin gene encodes a novel antibacterial peptide-like protein whose induction is cooperatively regulated by PGRP-LE and the JAK-STAT pathway.
Drosophila peptidoglycan recognition protein (PGRP)-LCx and -LCa are receptors that preferentiall... more Drosophila peptidoglycan recognition protein (PGRP)-LCx and -LCa are receptors that preferentially recognize meso-diaminopimelic acid (DAP)-type peptidoglycan (PGN) present in Gram-negative bacteria over lysine-type PGN of Gram-positive bacteria and initiate the IMD signaling pathway, whereas PGRP-LE plays a synergistic role in this process of innate immune defense. How these receptors can distinguish the two types of PGN remains unclear. Here the structure of the PGRP domain of Drosophila PGRP-LE in complex with tracheal cytotoxin (TCT), the monomeric DAP-type PGN, reveals a buried ionic interaction between the unique carboxyl group of DAP and a previously unrecognized arginine residue. This arginine is conserved in the known DAP-type PGN-interacting PGRPs and contributes significantly to the affinity of the protein for the ligand. Unexpectedly, TCT induces infinite head-to-tail dimerization of PGRP-LE, in which the disaccharide moiety, but not the peptide stem, of TCT is positioned at the dimer interface. A sequence comparison suggests that TCT induces heterodimerization of the ectodomains of PGRP-LCx and -LCa in a closely analogous manner to prime the IMD signaling pathway, except that the heterodimer formation is nonperpetuating. Innate immune defenses against pathogens are initiated by pattern recognition receptors that bind conserved stereotypical, rather than particular, molecular structures present in a wide spectrum of microorganisms but absent in the host (1). A representative example of such structures is peptidoglycan (PGN), 3 the major constituent of the cell wall of both Gram-positive and -negative bacteria. The peptidoglycan recognition protein (PGRP) family is a class of pattern recognition receptors that bind, and sometimes cleave, PGN. A total of 13 and four PGRP family members have been identified in Drosophila and humans, respectively (2-5). PGRPs are often characterized based on their * This work was supported by Creative Research Initiatives of the Korean Ministry of Science and Technology. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The atomic coordinates and structure factors (code 2CB3) have been deposited in the Protein Data Bank,
Pathogen recognition is the first and crucial step in innate immunity. Molecular families involve... more Pathogen recognition is the first and crucial step in innate immunity. Molecular families involved in the recognition of pathogens and activation of the innate immune responses in immunoreactive cells include the Toll-like receptor family in mammals and the peptidoglycan recognition protein (PGRP) family in Drosophila, which sense microorganisms in an extracellular or luminal compartment. Other emerging families are the intracellular recognition molecules for bacteria, such as nucleotide binding and oligomerization domain-like receptors in mammals and PGRPLE in Drosophila, several of which have been shown to detect structures of bacterial peptidoglycan in the host cell cytosol. Exciting advances in recent studies on autophagy indicate that macroautophagy (referred to here as autophagy) is selectively induced by intracellular recognition molecules and has a crucial role in the elimination of intracellular pathogens, including bacteria, viruses and parasites. This review discusses recent studies related to intracellular recognition molecules and innate immune responses to intracellular pathogens, and highlights the role of autophagy in innate immunity.
The modori phenomenon during surimi production is caused by endogenous proteinases, especially ca... more The modori phenomenon during surimi production is caused by endogenous proteinases, especially cathepsin L and myofibril-bound serine proteinase (MBSP). Cathepsin L from the skeletal muscle of blue scad (Decapterus maruadsi) was purified to homogeneity by ammonium sulphate fractionation and a series of column chromatographies and revealed a single band with molecular mass of 30 kDa on SDS-PAGE. Peptide mass fingerprinting (PMF) obtained three fragments with 48 amino acid residues, which were highly identical to cathepsin L from other fish species. Its optimal pH and temperature were 5.5 and 55 °C, respectively. Meanwhile, MBSP was purified from the skeletal muscle of blue scad, and the roles of cathepsin L and MBSP in the degradation of myofibrillar proteins were compared. The results indicated that MBSP is more effective than cathepsin L in promoting the degradation of myofibrillar proteins, especially myosin heavy chain (MHC), suggesting that MBSP plays a more significant role.
Hrp48, a Drosophila hnRNPA/B Homolog, Binds and Regulates Translation of oskar mRNA germline dete... more Hrp48, a Drosophila hnRNPA/B Homolog, Binds and Regulates Translation of oskar mRNA germline determinants. oskar is both necessary and sufficient for pole plasm formation (Ephrussi and Lehmann, 1992; Lehmann and Nu ¨sslein-Volhard, 1986). oskar mu-
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