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Ashaiba A, Arun AB, Prasad KS, Tellis RC. Leptospiral sphingomyelinase Sph2 as a potential biomarker for diagnosis of leptospirosis. J Microbiol Methods 2022; 203:106621. [PMID: 36375539 DOI: 10.1016/j.mimet.2022.106621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 11/07/2022] [Accepted: 11/07/2022] [Indexed: 11/13/2022]
Abstract
Leptospirosis is an underestimated infectious tropical disease caused by the spirochetes belonging to the genus Leptospira. Leptospirosis is grossly underdiagnosed due to its myriad symptoms, varying from mild febrile illness to severe haemorrhage. Laboratory tests for leptospirosis is an extremely important and potent way for disease diagnosis, as the clinical manifestations are very similar to other febrile diseases. Currently available diagnostic techniques are time-consuming, require expertise and sophisticated instruments, and cannot identify the disease at an early phase of infection. Early diagnosis of leptospirosis is the need of the hour while considering the severe complications after the infection and the rate of mortality after misdiagnosis. Secretion of Leptospira-specific sphingomyelinases in leptospirosis patient's urine within a few days of the onset of infection is quite common and is a virulence factor present only in pathogenic Leptospira species. Herein, the structural and functional importance of leptospiral sphingomyelinase Sph2 in leptospirosis pathogenesis, as well as the potential of screening urinary Sph2 for diagnosis and the scope for developing a rapid and easily affordable point-of-care test for urinary leptospiral sphingomyelinase Sph2 as an alternative to current diagnostic methods are discussed.
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Affiliation(s)
- A Ashaiba
- Department of Microbiology, Yenepoya Medical College, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India; Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India
| | - A B Arun
- Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India
| | - K Sudhakara Prasad
- Nano Materials Research Laboratory, Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India; Centre for Nutrition Studies, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India.
| | - Rouchelle C Tellis
- Department of Microbiology, Yenepoya Medical College, Yenepoya (Deemed to be University), Deralakatte, Mangalore 575 018, India.
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Jeon J, Kang S, Hur JK, Rho M. Metagenomic characterization of sphingomyelinase C in the microbiome of humans and environments. Front Cell Infect Microbiol 2022; 12:1015706. [PMID: 36467737 PMCID: PMC9710629 DOI: 10.3389/fcimb.2022.1015706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 10/25/2022] [Indexed: 09/25/2023] Open
Abstract
Bacterial sphingomyelinases (SMases) hydrolyze sphingomyelin and play an important role in membrane dynamics and the host immune system. While the number of sequenced genomes and metagenomes is increasing, a limited number of experimentally validated SMases have been reported, and the genomic diversity of SMases needs to be elucidated extensively. This study investigated the sequence and structural characteristics of SMases in bacterial genomes and metagenomes. Using previously identified SMases, such as the β-toxin of Staphylococcus aureus, we identified 276 putative SMases and 15 metagenomic SMases by a sequence homology search. Among the predicted metagenomic SMases, six non-redundant metagenomic SMases (M-SMase1-6) were selected for further analysis. The predicted SMases were confirmed to contain highly conserved residues in the central metal-binding site; however, the edge metal-binding site showed high diversity according to the taxon. In addition, protein structure modeling of metagenomic SMases confirmed structural conservation of the central metal-binding site and variance of the edge metal-binding site. From the activity assay on M-SMase2 and M-SMase5, we found that they displayed sphingomyelinase activity compared to Bacillus cereus SMase. This study elucidates a comprehensive genomic characterization of SMases and provides insight into the sequence-structure-activity relationship.
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Affiliation(s)
- Jehyun Jeon
- Department of Computer Science, Hanyang University, Seoul, South Korea
| | - Seunghun Kang
- Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, South Korea
| | - Junho K. Hur
- Graduate School of Biomedical Science and Engineering, Hanyang University, Seoul, South Korea
- Department of Genetics, College of Medicine, Hanyang University, Seoul, South Korea
- Hanyang Institute of Bioscience and Biotechnology, Hanyang University, Seoul, South Korea
| | - Mina Rho
- Department of Computer Science, Hanyang University, Seoul, South Korea
- Hanyang Institute of Bioscience and Biotechnology, Hanyang University, Seoul, South Korea
- Department of Biomedical Informatics, Hanyang University, Seoul, South Korea
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Abstract
Bacterial sphingomyelinases and phospholipases are a heterogeneous group of esterases which are usually surface associated or secreted by a wide variety of Gram-positive and Gram-negative bacteria. These enzymes hydrolyze sphingomyelin and glycerophospholipids, respectively, generating products identical to the ones produced by eukaryotic enzymes which play crucial roles in distinct physiological processes, including membrane dynamics, cellular signaling, migration, growth, and death. Several bacterial sphingomyelinases and phospholipases are essential for virulence of extracellular, facultative, or obligate intracellular pathogens, as these enzymes contribute to phagosomal escape or phagosomal maturation avoidance, favoring tissue colonization, infection establishment and progression, or immune response evasion. This work presents a classification proposal for bacterial sphingomyelinases and phospholipases that considers not only their enzymatic activities but also their structural aspects. An overview of the main physiopathological activities is provided for each enzyme type, as are examples in which inactivation of a sphingomyelinase- or a phospholipase-encoding gene impairs the virulence of a pathogen. The identification of sphingomyelinases and phospholipases important for bacterial pathogenesis and the development of inhibitors for these enzymes could generate candidate vaccines and therapeutic agents, which will diminish the impacts of the associated human and animal diseases.
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Narayanavari SA, Lourdault K, Sritharan M, Haake DA, Matsunaga J. Role of sph2 Gene Regulation in Hemolytic and Sphingomyelinase Activities Produced by Leptospira interrogans. PLoS Negl Trop Dis 2015; 9:e0003952. [PMID: 26274394 PMCID: PMC4537108 DOI: 10.1371/journal.pntd.0003952] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 07/06/2015] [Indexed: 12/19/2022] Open
Abstract
Pathogenic members of the genus Leptospira are the causative agents of leptospirosis, a neglected disease of public and veterinary health concern. Leptospirosis is a systemic disease that in its severest forms leads to renal insufficiency, hepatic dysfunction, and pulmonary failure. Many strains of Leptospira produce hemolytic and sphingomyelinase activities, and a number of candidate leptospiral hemolysins have been identified based on sequence similarity to well-characterized bacterial hemolysins. Five of the putative hemolysins are sphingomyelinase paralogs. Although recombinant forms of the sphingomyelinase Sph2 and other hemolysins lyse erythrocytes, none have been demonstrated to contribute to the hemolytic activity secreted by leptospiral cells. In this study, we examined the regulation of sph2 and its relationship to hemolytic and sphingomyelinase activities produced by several L. interrogans strains cultivated under the osmotic conditions found in the mammalian host. The sph2 gene was poorly expressed when the Fiocruz L1-130 (serovar Copenhageni), 56601 (sv. Lai), and L495 (sv. Manilae) strains were cultivated in the standard culture medium EMJH. Raising EMJH osmolarity to physiological levels with sodium chloride enhanced Sph2 production in all three strains. In addition, the Pomona subtype kennewicki strain LC82-25 produced substantially greater amounts of Sph2 during standard EMJH growth than the other strains, and sph2 expression increased further by addition of salt. When 10% rat serum was present in EMJH along with the sodium chloride supplement, Sph2 production increased further in all strains. Osmotic regulation and differences in basal Sph2 production in the Manilae L495 and Pomona strains correlated with the levels of secreted hemolysin and sphingomyelinase activities. Finally, a transposon insertion in sph2 dramatically reduced hemolytic and sphingomyelinase activities during incubation of L. interrogans at physiologic osmolarity. Complementation of the mutation with the sph2 gene partially restored production of hemolytic and sphingomyelinase activities. These results indicate that the sph2 gene product contributes to the hemolytic and sphingomyelinase activities secreted by L. interrogans and most likely dominates those functions under the culture condition tested. The spirochete Leptospira causes leptospirosis, a potentially deadly disease of humans and animals. Candidate factors that promote infection include hemolysins encoded by several leptospiral genes. Hemolysins rupture red blood cells in vitro. Some hemolysins are sphingomyelinases, which target sphingomyelin in the host cell membrane. Hemolysins have the potential to disrupt organ function during infection. It is not known which hemolysins and sphingomyelinases are responsible for the hemolytic and sphingomyelinase activities secreted by L. interrogans. We found that the production of hemolytic activity is regulated and is tied to expression of sph2, which encodes a hemolysin with sphingomyelinase, cytotoxic, and fibronectin-binding activities. Hemolytic and sphingomyelinase activities and sph2 expression were higher when the osmolarity of the culture medium was raised to the level found in the mammalian host. Similarly, sph2 expression was substantially higher in an L. interrogans strain that secreted large amounts of hemolytic and sphingomyelinase activities than in a strain that generated negligible amounts. Most importantly, disruption of the sph2 gene eliminated hemolysin production and yielded substantially less sphingomyelinase than the wild-type strain. Our findings indicate that sph2 is a major contributor to the hemolytic and sphingomyelinase activities secreted by L. interrogans and that the hemolytic and sphingomyelinase activities measured in standard L. interrogans cultures may underestimate the levels produced during infection.
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Affiliation(s)
| | - Kristel Lourdault
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America; Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
| | - Manjula Sritharan
- Department of Animal Biology, University of Hyderabad, Hyderabad, India
| | - David A Haake
- Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, California, United States of America; Department of Urology, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, California, United States of America; Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, California, United States of America; Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - James Matsunaga
- Research Service, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America; Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
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The Mucin Box and Signal/Anchor Sequence of Rat Neutral Ceramidase Recruit Bacterial Sphingomyelinase to the Plasma Membrane. Biosci Biotechnol Biochem 2014; 75:987-90. [DOI: 10.1271/bbb.100767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Horibata Y, Sueyoshi N, Ito M. Expression of a Functional Sphingomyelinase ofPseudomonassp. TK4 in Mammalian Cells. Biosci Biotechnol Biochem 2014; 71:603-6. [PMID: 17284826 DOI: 10.1271/bbb.60544] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We report here the expression of a bacterial sphingomyelinase in mammalian cells as a functionally active form. A chimeric Pseudomonas sphingomyelinase fused with the lysosomal sorting motif of lysosomal acid phosphatase was sorted to lysosomes in mammalian cells. As expected, the chimeric SMase hydrolyzed sphingomyelin in vivo to produce ceramide, part of which was converted to glucosylceramide.
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Affiliation(s)
- Yasuhiro Horibata
- Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan
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Sogabe T, Ota H, Iwasaki M, Sakasegawa SI, Tamura T. Sphingomyelinase C from Streptomyces sp. A9107: unusual primary structure for bacterial sphingomyelinase C. J Biosci Bioeng 2012; 114:398-401. [PMID: 22664344 DOI: 10.1016/j.jbiosc.2012.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/02/2012] [Accepted: 05/07/2012] [Indexed: 10/28/2022]
Abstract
A sphingomyelinase C (SMase) was identified in the culture supernatant of Streptomyces sp. A9107 (S-SMase). Although S-SMase seems to be a typical bacterial SMase, the primary structure of S-SMase was unusual for known bacterial SMase. The gene was functionally overexpressed in the culture medium of recombinant Rhodococcus erythropolis.
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Affiliation(s)
- Takayuki Sogabe
- Asahi Kasei Pharma Corporation, Diagnostics R&D, 632-1 Mifuku, Izunokuni-shi, Shizuoka 410-2321, Japan
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Narayanavari SA, Kishore NM, Sritharan M. Structural analysis of the Leptospiral sphingomyelinases: in silico and experimental evaluation of Sph2 as an Mg-dependent sphingomyelinase. J Mol Microbiol Biotechnol 2012; 22:24-34. [PMID: 22441407 DOI: 10.1159/000337013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Leptospiral sphingomyelinases are candidate virulence factors present only in pathogenic Leptospira spp. Leptospira interrogans serovar Lai encodes Sph1, Sph2, Sph3, Sph4 and SphH. Except for Sph4, they all possess the exo-endo-phosphatase domain that groups them under the DNase I superfamily. METHODS, RESULTS AND CONCLUSIONS Modeling of exo-endo-phosphatase domains reveals high-level structural similarity of Sph2 with the crystal structure of SmcL and BC SMase sphingomyelinases from Listeria ivanovii and Bacillus cereus, respectively. A β-hairpin loop, essential for host cell membrane interaction, is absent in leptospiral sphingomyelinases. Instead, several aromatic amino acids were oriented outward from the surface of these molecules and formed clusters of hydrophobic regions that possibly enables the anchoring of these molecules into the host cell membrane, as demonstrated in Sph2 and Sph3. Sph2 is unique and possesses the Mg(++)-binding Glu53 residue in the metal-binding site and two His residues (His151 and His286) in the catalytic site. We demonstrate experimentally the Mg(++)-dependent hemolysis of erythrocytes by rSph2 and its ability to cleave sphingomyelin to ceramide. Anti-Sph2 antibodies neutralized the hemolytic activity of Sph2. In conclusion, we provide evidence showing that Sph2 is a Mg(++)-dependent hemolysin with both sphingomyelinase and hemolytic activities.
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Affiliation(s)
- Suneel A Narayanavari
- Department of Animal Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
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Narayanavari SA, Sritharan M, Haake DA, Matsunaga J. Multiple leptospiral sphingomyelinases (or are there?). MICROBIOLOGY-SGM 2012; 158:1137-1146. [PMID: 22422753 DOI: 10.1099/mic.0.057737-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Culture supernatants of leptospiral pathogens have long been known to haemolyse erythrocytes. This property is due, at least in part, to sphingomyelinase activity. Indeed, genome sequencing reveals that pathogenic Leptospira species are richly endowed with sphingomyelinase homologues: five genes have been annotated to encode sphingomyelinases in Leptospira interrogans. Such redundancy suggests that this class of genes is likely to benefit leptospiral pathogens in their interactions with the mammalian host. Surprisingly, sequence comparison with bacterial sphingomyelinases for which the crystal structures are known reveals that only one of the leptospiral homologues has the active site amino acid residues required for enzymic activity. Based on studies of other bacterial toxins, we propose that leptospiral sphingomyelinase homologues, irrespective of their catalytic activity, may possess additional molecular functions that benefit the spirochaete. Potential secretion pathways and roles in pathogenesis are discussed, including nutrient acquisition, dissemination, haemorrhage and immune evasion. Although leptospiral sphingomyelinase-like proteins are best known for their cytolytic properties, we believe that a better understanding of their biological role requires the examination of their sublytic properties as well.
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Affiliation(s)
| | - Manjula Sritharan
- Department of Animal Sciences, University of Hyderabad, Hyderabad, India
| | - David A Haake
- Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.,Department of Urology, University of California at Los Angeles, Los Angeles, CA, USA.,Division of Infectious Diseases, VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, CA, USA
| | - James Matsunaga
- Research Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
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Li C, Tao J, Mao D, He C. A novel manganese efflux system, YebN, is required for virulence by Xanthomonas oryzae pv. oryzae. PLoS One 2011; 6:e21983. [PMID: 21789199 PMCID: PMC3136493 DOI: 10.1371/journal.pone.0021983] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 06/14/2011] [Indexed: 12/01/2022] Open
Abstract
Manganese ions (Mn2+) play a crucial role in virulence and protection against oxidative stress in bacterial pathogens. Such pathogens appear to have evolved complex mechanisms for regulating Mn2+ uptake and efflux. Despite numerous studies on Mn2+ uptake, however, only one efflux system has been identified to date. Here, we report on a novel Mn2+ export system, YebN, in Xanthomonas oryzae pv. oryzae (Xoo), the causative agent of bacterial leaf blight. Compared with wild-type PXO99, the yebN mutant was highly sensitive to Mn2+ and accumulated high concentrations of intracellular manganese. In addition, we found that expression of yebN was positively regulated by Mn2+ and the Mn2+-dependent transcription regulator, MntR. Interestingly, the yebN mutant was more tolerant to methyl viologen and H2O2 in low Mn2+ medium than PXO99, but more sensitive in high Mn2+ medium, implying that YebN plays an important role in Mn2+ homoeostasis and detoxification of reactive oxygen species (ROS). Notably, deletion of yebN rendered Xoo sensitive to hypo-osmotic shock, suggesting that YebN may protect against such stress. That mutation of yebN substantially reduced the Xoo growth rate and lesion formation in rice implies that YebN could be involved in Xoo fitness in host. Although YebN has two DUF204 domains, it lacks homology to any known metal transporter. Hence, this is the first report of a novel metal export system that plays essential roles in hypo-osmotic and oxidative stress, and virulence. Our results lay the foundations for elucidating the complex and fascinating relationship between metal homeostasis and host-pathogen interactions.
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Affiliation(s)
- Chunxia Li
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Jun Tao
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Daqing Mao
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Chaozu He
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Hainan University, Haikou, Hainan, China
- * E-mail:
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Mendoza-Macías CL, Barrios-Ceballos MP, Anaya-Velázquez F, Nakada-Tsukui K, Nozaki T, Padilla-Vaca F. Entamoeba histolytica: Molecular cloning and characterization of a novel neutral sphingomyelinase. Exp Parasitol 2010; 125:279-85. [DOI: 10.1016/j.exppara.2010.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 01/28/2010] [Accepted: 02/01/2010] [Indexed: 01/21/2023]
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Clarke CJ, Snook CF, Tani M, Matmati N, Marchesini N, Hannun YA. The extended family of neutral sphingomyelinases. Biochemistry 2006; 45:11247-56. [PMID: 16981685 DOI: 10.1021/bi061307z] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The neutral sphingomyelinases (N-SMases) are considered major candidates for mediating the stress-induced production of ceramide, and N-SMase activity has been identified, characterized, and cloned from bacteria, yeast, and mammalian cells. Although the level of identity between these enzymes is low, a number of key residues thought to be involved in metal binding and catalysis are conserved. This has led to the suggestion of a common catalytic mechanism, and thus, these enzymes are considered to form an extended family of N-SMases. Despite considerable research into N-SMase activity in cell culture and various tissues, the lack, until recently, of molecular identification of specific N-SMase enzymes had precluded specific insights into the regulation, physiological, and pathological roles of these proteins. In this review, we summarize, for the first time, current knowledge of the N-SMase family, focusing on cloned members from bacteria, yeast, and mammalian cells. We also briefly consider the major future directions for N-SMase research which promises highly significant and specific insight into sphingolipid-mediated functions.
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Affiliation(s)
- Christopher J Clarke
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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Hossain MS, Hamamoto H, Matsumoto Y, Razanajatovo IM, Larranaga J, Kaito C, Kasuga H, Sekimizu K. Use of Silkworm Larvae to Study Pathogenic Bacterial Toxins. ACTA ACUST UNITED AC 2006; 140:439-44. [PMID: 16891331 DOI: 10.1093/jb/mvj171] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Injection of stationary phase culture-supernatants of Staphylococcus aureus and Pseudomonas aeruginosa into the hemolymph of silkworm larvae caused their death, whereas a culture-supernatant of a non-pathogenic strain of Escherichia coli did not. A culture-supernatant of a mutant of agr, a global virulence regulator of S. aureus that is required for exotoxin production, was much less toxic to silkworm larvae. A culture-supernatant of a disruption mutant of the S. aureus beta-toxin gene did not kill larvae, whereas one of a deletion mutant of alpha-toxin, gamma-toxin, or aureolysin killed larvae, indicating that the beta-toxin gene is required for staphylococcal supernatant-mediated killing of silkworm larvae. The 50% lethal doses (LD50) of staphylococcal alpha-toxin and beta-toxin, Pseudomonas exotoxin A and diphtheria toxin were 12 microg/g, 9 microg/g, 0.14 microg/g and 1.1 microg/g, respectively. As the purified toxins killed the larvae, silkworm larvae could be used as a model to study the actions of pathogenic bacterial toxins in animal bodies.
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Affiliation(s)
- Muktadir S Hossain
- Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-chome, Hongo, Bunkyo-ku, Tokyo 113-0033.
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Artiushin S, Timoney JF, Nally J, Verma A. Host-inducible immunogenic sphingomyelinase-like protein, Lk73.5, of Leptospira interrogans. Infect Immun 2004; 72:742-9. [PMID: 14742516 PMCID: PMC321616 DOI: 10.1128/iai.72.2.742-749.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Leptospira interrogans causes a variety of clinical syndromes in animals and humans. Although much information has accumulated on the importance of leptospiral lipopolysaccharide in protective antibody responses, relatively little is known about proteins that participate in immune responses. Identification of those proteins induced only in the host is particularly difficult. Using a novel double-antibody screen designed to identify clones in a gene library of L. interrogans serovar Pomona expressing host-inducible proteins, we have characterized a gene (lk75.3) encoding a sphingomyelinase-like preprotein of 648 amino acids with cytotoxic activity for equine pulmonary endothelial cells and weak hemolytic activity for equine and rabbit erythrocytes. lk73.5 was found as a single gene copy in all serovars of L. interrogans but not in other Leptospira spp. except L. inadai. The open reading frame (ORF) for Lk73.5 is followed by another partially homologous sequence containing an ORF (sph-like 2) for a 28.7-kDa peptide. Lk73.5 and Sph-like 2 share 95.1 and 97.7% amino acid identity with putative sphingomyelinases Sph2 and Sph1 (N terminus) from L. interrogans serovar Lai (S.-X. Ren, G. Fu, X.-G. Jiangk, R. Zeng, Y.-G. Miao, H. Xu, Y.-X. Zhang, H. Xiong, G. Lu, L.-F. Lu, H.-Q. Jiang, J. Jia, Y.-F. Tu, J.-X. Jiang, W.-Y. Gu, Y.-Q. Zhang, Z. Cai, H.-H. Sheng, H.-F. Yin, Y. Zhang, G.-F. Zhu, M. Wank, H.-L. Huangk, Z. Qian, S.-Y. Wang, Wei Ma, Z.-J. Yao, Y. Shen, B.-Q. Qiang, Q.-C. Xia, X.-K. Guo, A. Danchinq, I. S. Girons, R. L. Somerville, Y.-M. Wen, M.-H. Shik, Z. Chen, J.-G. Xuk, and G.-P. Zhao, Nature 422:88-893, 2003). Substantial homologies to sphingomyelinases from other leptospiras and other bacteria are also present. Lk73.5 was not detected in leptospiras cultured at 30 or 37 degrees C. The recombinant protein reacted strongly with sera from recently infected mares but not with sera from horses vaccinated with commercial pentavalent bacterin. The host-inducible immunogenic Lk73.5 should have value in distinguishing vaccine from infection immune response.
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Affiliation(s)
- S Artiushin
- Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky 40546, USA.
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Luberto C, Stonehouse MJ, Collins EA, Marchesini N, El-Bawab S, Vasil AI, Vasil ML, Hannun YA. Purification, characterization, and identification of a sphingomyelin synthase from Pseudomonas aeruginosa. PlcH is a multifunctional enzyme. J Biol Chem 2003; 278:32733-43. [PMID: 12799377 DOI: 10.1074/jbc.m300932200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sphingomyelin synthase is the enzyme that synthesizes sphingomyelin (SM) in mammalian cells by transferring a phosphorylcholine moiety from phosphatidylcholine to ceramide. Despite its importance, the gene and/or the protein responsible for this activity has not yet been identified. Here we report the purification, identification, and biochemical characterization of an enzymatic activity that synthesizes SM in Pseudomonas aeruginosa. SM synthase-like activity was found secreted in the culture medium of P. aeruginosa, strains PA01 and PAK, whereas it could not be detected in cultures of Escherichia coli. From the medium of PAK cultures, SM synthase was purified through sequential chromatographic columns. After separation on polyacrylamide-SDS gels and visualization by silver staining, the purified enzyme showed two bands, one of approximately 75 kDa and one of 30-35 kDa. Interestingly, the highly purified SM synthase preparation also showed neutral sphingomyelinase activity. We therefore investigated whether the protein we purified as SM synthase could actually be the previously identified PlcH, a 78-kDa phospholipase C known to hydrolyze phosphatidylcholine and SM in P. aeruginosa. First, the purified SM synthase preparation contained a 78-kDa protein that reacted with monoclonal antibodies raised against purified PlcH. Second, purified PlcH showed SM synthase activity. Third, using different knockout mutant strains for the PlcH operon, PlcH was found to be necessary for SM synthase activity in P. aeruginosa. Interestingly, SM synthase activity was specific to the Pseudomonas PlcH as other bacterial phospholipases did not display SM synthase activity. Biochemical studies on the Pseudomonas SM synthase confirmed that it is a transferase, similar to the mammalian enzyme, that specifically recognizes the choline head-group and the primary hydroxyl on ceramide. This SM synthase did not have reverse transferase activity. In conclusion, the Pseudomonas PlcH also exerts SM synthase activity; therefore, for the first time, we have identified a structural gene for a SM synthase.
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Affiliation(s)
- Chiara Luberto
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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Kehres DG, Maguire ME. Emerging themes in manganese transport, biochemistry and pathogenesis in bacteria. FEMS Microbiol Rev 2003; 27:263-90. [PMID: 12829271 DOI: 10.1016/s0168-6445(03)00052-4] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Though an essential trace element, manganese is generally accorded little importance in biology other than as a cofactor for some free radical detoxifying enzymes and in the photosynthetic photosystem II. Only a handful of other Mn2+-dependent enzymes are known. Recent data, primarily in bacteria, suggest that Mn2+-dependent processes may have significantly greater physiological importance. Two major classes of prokaryotic Mn2+ uptake systems have now been described, one homologous to eukaryotic Nramp transporters and one a member of the ABC-type ATPase superfamily. Each is highly selective for Mn2+ over Fe2+ or other transition metal divalent cations, and each can accumulate millimolar amounts of intracellular Mn2+ even when environmental Mn2+ is scarce. In Salmonella enterica serovar Typhimurium, simultaneous mutation of both types of transporter results in avirulence, implying that one or more Mn2+-dependent enzymes is essential for pathogenesis. This review summarizes current literature on Mn2+ transport, primarily in the Bacteria but with relevant comparisons to the Archaea and Eukaryota. Mn2+-dependent enzymes are then discussed along with some speculations as to their role(s) in cellular physiology, again primarily in Bacteria. It is of particular interest that most of the enzymes which interconvert phosphoglycerate, pyruvate, and oxaloacetate intermediates are either strictly Mn2+-dependent or highly stimulated by Mn2+. This suggests that Mn2+ may play an important role in central carbon metabolism. Further studies will be required, however, to determine whether these or other actions of Mn2+ within the cell are the relevant factors in pathogenesis.
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Affiliation(s)
- David G Kehres
- Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4965, USA.
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Abstract
This paper reviews our present knowledge of sphingomyelinases as enzymes, and as enzymes acting on a membrane constituent lipid, sphingomyelin. Six types of sphingomyelinases are considered, namely acidic, secretory, Mg(2+)-dependent neutral, Mg(2+)-independent neutral, alkaline, and bacterial enzymes with both phospholipase C and sphingomyelinase activity. Sphingomyelinase assay methods and specific inhibitors are reviewed. Kinetic and mechanistic studies are summarized, a kinetic model and a general-base catalytic mechanism are proposed. Sphingomyelinase-membrane interactions are considered from the point of view of the influence of lipids on the enzyme activity. Moreover, effects of sphingomyelinase activity on membrane architecture (increased membrane permeability, membrane aggregation and fusion) are described. Finally, a number of open questions on the above topics are enunciated.
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Affiliation(s)
- Félix M Goñi
- Unidad de Biofísica (CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080, Bilbao, Spain.
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