RegR, a Global LacI/GalR Family Regulator, Modulates Virulence and Competence in Streptococcus pneumoniae

ABSTRACT The homolactic and catalase-deficient pathogen Streptococcus pneumoniae is not only tolerant to oxygen but requires the activity of its NADH oxidase, Nox, to develop optimal virulence and competence for genetic transformation. In this work, we show that the global regulator RegR is also involved in these traits. Genetic dissection revealed that RegR regulates competence and the expression of virulence factors, including hyaluronidase. In bacteria grown in vitro, RegR represses hyaluronidase. At neutral pH, it increases adherence to A549 epithelial cells, and at alkaline pH, it acts upstream of the CiaRH two-component signaling system to activate competence. These phenotypes are not associated with changes in antibiotic resistance, central metabolism, and carbohydrate utilization. Although the RegR0 (where 0 indicates the loss of the protein) mutation is sufficient to attenuate experimental virulence of strain 23477 in mice, the introduction of an additional hyl0 (where 0 indicates the loss of function) mutation in the RegR0 strain 23302 dramatically reduces its virulence. This indicates that residual virulence of the RegR0 Hyl+ derivative is due to hyaluronidase and supports the dual role of RegR in virulence. This LacI/GalR regulator, not essential for in vitro growth in rich media, is indeed involved in the adaptive response of the pneumococcus via its control of competence, adherence, and virulence.

Download Full-text

Group B Streptococcal and Pneumococcal Sepsis in Newborn Infants: The Role of Pneumococcal Antibody

PEDIATRICS ◽

10.1542/peds.62.4.620 ◽

1978 ◽

Vol 62 (4) ◽

pp. 620-621

Author(s):

Gerald W. Fischer ◽

James W. Bass ◽

George H. Lowell ◽

Martin H. Crumrine

Keyword(s):

Streptococcus Pneumoniae ◽

Hydrochloric Acid ◽

Group B Streptococcus ◽

Newborn Infants ◽

Polysaccharide Antigen ◽

Type Iii ◽

Pneumococcal Sepsis ◽

Group B

The article by Bortolussi et al. on pneumococcal septicemia and meningitis in the neonat (Pediatrics 60:352, September 1977) was of great interest to us, since we have been analyzing the effect of antibody directed against Streptococcus pneumoniae on group B Streptococcus type III. We have recently shown (unpublished data) that antibody directed against S. pneumoniae type 14 precipitates the hot hydrochloric acid-extracted polysaccharide antigen of group B Streptococcus type III. Further studies have shown that this antibody is opsonic for group B Streptococcus type III in an in vitro bactericidal assay and protective in a suckling rat model of group B Streptococcus type III sepsis.1

Download Full-text

Absent in melanoma 2 inflammasome is required for host defence against Streptococcus pneumoniae infection

Innate Immunity ◽

10.1177/1753425919860252 ◽

2019 ◽

Vol 25 (7) ◽

pp. 412-419 ◽

Cited By ~ 2

Author(s):

Siwei Feng ◽

Tingting Chen ◽

Guihua Lei ◽

Fengqing Hou ◽

Jiali Jiang ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Pneumococcal Infection ◽

Host Defence ◽

Mortality And Morbidity ◽

Caspase 1 ◽

Pyrin Domain ◽

Increased Susceptibility

Streptococcus pneumoniae, a leading cause of invasive pneumococcal disease, is responsible for high mortality and morbidity worldwide. A previous study showed that the NLR family pyrin domain containing 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasomes are essential for caspase-1 activation and IL-1β production in the host response to S. pneumoniae infection. The function of NLRP3 in host innate immunity to S. pneumoniae was studied in vivo and in vitro. However, the role of AIM2 in host defence against S. pneumoniae remains unclear. Here, we show that AIM2-deficient (AIM2–/–) mice display increased susceptibility to intra-nasal infection with S. pneumoniae in comparison to wild type mice and that this susceptibility was associated with defective IL-1β production. Macrophages from AIM2–/– mice infected with S. pneumoniae showed impaired secretion of IL-1β as well as activation of the inflammasome, as determined by the oligomerisation of apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1 activation. Taken together, these results indicate that the AIM2 inflammasome is essential for caspase-1-dependent cytokine IL-1β production and eventual protection from pneumococcal infection in mice.

Download Full-text

RACK1 Acts as a Potential Tumor Promoter in Colorectal Cancer

Gastroenterology Research and Practice ◽

10.1155/2019/5625026 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8

Author(s):

Xue-Yang Li ◽

Yi Hu ◽

Nian-Shuang Li ◽

Jian-Hua Wan ◽

Yin Zhu ◽

...

Keyword(s):

Colorectal Cancer ◽

The Cancer Genome Atlas ◽

Biological Role ◽

Tumor Promoter ◽

Migration And Invasion ◽

Loss Of Function ◽

Normal Tissues ◽

Geo Dataset

Background. The receptor of activated protein kinase C 1 (RACK1) promotes the progression and invasion of several cancers. However, the role of RACK1 in the pathogenesis of colorectal cancer (CRC) has not been clearly defined. Herein, we aimed to investigate the biological role of RACK1 in CRC. Materials and Methods. The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) dataset were searched, and the expression of RACK1 in CRC tissues and adjacent normal tissues was evaluated. Immunohistochemical staining was performed to detect the expression of RACK1 in human CRC, adenoma, and normal tissues. Western blotting was used to detect the expression of RACK1 in human CRC cell lines. Functional assays, such as BrdU, colony formation, and wound healing and transwell invasion assays, were used to explore the biological role of RACK1 in CRC. Results. RACK1 was upregulated in CRC tissues compared with its expression in adjacent normal tissues in TCGA and the GEO dataset (P<0.05). Moreover, RACK1 was significantly overexpressed in CRC and adenoma tissues compared with its expression in normal tissues (P<0.05). Loss-of-function experiments showed that RACK1 promoted cell proliferation, migration, and invasion in vitro. Conclusions. Our data indicated that RACK1, as an oncogene, markedly promoted the progression of CRC, which suggested that RACK1 is a potential therapeutic target for CRC management.

Download Full-text

Complement Receptor 1 Expression on Mouse Erythrocytes Mediates Clearance of Streptococcus pneumoniae by Immune Adherence

Infection and Immunity ◽

10.1128/iai.01263-09 ◽

2010 ◽

Vol 78 (7) ◽

pp. 3129-3135 ◽

Cited By ~ 23

Author(s):

Jie Li ◽

Jennifer P. Wang ◽

Ionita Ghiran ◽

Anna Cerny ◽

Alexander J. Szalai ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Direct Evidence ◽

Wild Type Mouse ◽

Complement Receptor ◽

Blood Clearance ◽

Wild Type ◽

Immune Adherence ◽

Complement Receptor 1

ABSTRACT Complement-containing immune complexes can be presented to phagocytes by human erythrocytes bearing complement receptor 1 (CR1). Although this has long been assumed to be a mechanism by which humans are able to protect themselves from “extracellular” bacteria such as pneumococci, there is little direct evidence. In these studies we have investigated this question by comparing results for erythrocytes from transgenic mice expressing human CR1 on their erythrocytes to the results for wild-type mouse erythrocytes that do not express CR1. We demonstrate that human CR1 expression on murine erythrocytes allows immune adherence to beads opsonized with either mouse or human serum as a source of complement. The role of CR1 in immune adherence was supported by studies showing that it was blocked by the addition of antibody to human CR1. Furthermore, human CR1 expression enhances the immune adherence of opsonized pneumococci to erythrocytes in vitro, and the pneumococci attached to erythrocytes via CR1 can be transferred in vitro to live macrophages. Even more importantly, we observed that if complement-opsonized pneumococci are injected intravenously with CR1+ mouse erythrocytes into wild-type mice (after a short in vitro incubation), they are cleared faster than opsonized pneumococci similarly injected with wild-type mouse erythrocytes. Finally, we have shown that the intravenous (i.v.) injection of pneumococci into CR1+ mice also results in more rapid blood clearance than in wild-type mice. These data support that immune adherence via CR1 on erythrocytes likely plays an important role in the clearance of opsonized bacteria from human blood.

Download Full-text

LuxS impacts on LytA-dependent autolysis and on competence in Streptococcus pneumoniae

Microbiology ◽

10.1099/mic.0.28406-0 ◽

2006 ◽

Vol 152 (2) ◽

pp. 333-341 ◽

Cited By ~ 18

Author(s):

Susana Romao ◽

Guido Memmi ◽

Marco R. Oggioni ◽

Marie-Claude Trombe

Keyword(s):

Streptococcus Pneumoniae ◽

Regulatory Networks ◽

Cell Communication ◽

Genetic Dissection ◽

Developmental Physiology ◽

Adenosyl Methionine ◽

Sense And Respond ◽

The One ◽

The Impact

The ubiquitous protein LuxS with S-ribosylhomocysteinase activity is involved in S-adenosyl methionine detoxification, C-1 unit recycling and the production of autoinducers that allow the cell to sense and respond to cell density. Independent reports describe the impact of LuxS deficiency on Streptococcus pneumoniae virulence in the mouse. In vitro, LuxS deficiency confers discrete phenotypes. A combined approach using genetic dissection and mixed-culture experiments allowed the involvement of LuxS in the developmental physiology of S. pneumoniae to be investigated. Functional LuxS was found to be related on the one hand to down-regulation of competence, and on the other hand to attenuation of autolysis in cultures entering stationary phase. The competence phenotype of luxS mutant bacteria was complemented by media conditioned by competence-defective ComAB0 bacteria, but not by BSA. The autolytic phenotype was complemented by BSA, but not by conditioned supernatants. It is suggested that the impact of LuxS on competence, but not on autolysis, involves cell–cell communication. The phenotype of luxS mutant strains reveals a hierarchy in the competence regulatory networks of S. pneumoniae.

Download Full-text

Processing of progranulin into granulins involves multiple lysosomal proteases and is affected in frontotemporal lobar degeneration

10.21203/rs.3.rs-44128/v1 ◽

2020 ◽

Author(s):

Swetha Mohan ◽

Paul J. Sampognaro ◽

Andrea R. Argouarch ◽

Jason C. Maynard ◽

Anand Patwardhan ◽

...

Keyword(s):

Frontotemporal Lobar Degeneration ◽

Cathepsin L ◽

Dependent Manner ◽

Loss Of Function ◽

New Strategy ◽

Lysosomal Proteases ◽

Ph Dependent ◽

Increased Activity

Abstract Background: Progranulin loss-of-function mutations are linked to frontotemporal lobar degeneration with TDP-43 positive inclusions (FTLD-TDP-Pgrn). Progranulin (PGRN) is an intracellular and secreted pro-protein that is proteolytically cleaved into individual granulin peptides, which are increasingly thought to contribute to FTLD-TDP-Pgrn disease pathophysiology. Intracellular PGRN is processed into granulins in the endo-lysosomal compartments. Therefore, to better understand the conversion of intracellular PGRN into granulins, we systematically tested the ability of different classes of endo-lysosomal proteases at a range of pH setpoints.Results: In vitro cleavage assays identified multiple enzymes that can process human PGRN into multi- and single-granulin fragments in a pH-dependent manner. We confirmed the role of cathepsin B and cathepsin L in PGRN processing and showed that these and several previously unidentified lysosomal proteases (cathepsins E, G, K, S and V) are able to process PGRN in variable, pH-dependent manners. In addition, we have demonstrated a new role for asparagine endopeptidase (AEP) in processing PGRN, with AEP having the unique ability to liberate granulin F from the pro-protein. Brain tissue from individuals with FTLD-TDP-Pgrn show increased PGRN processing to granulin F, correlating with increased activity of AEP, in a region-specific manner. Conclusions: This study demonstrates that multiple lysosomal proteases may work in concert to liberate granulins and implicates both AEP and granulin F in the neurobiology of FTLD-TDP-Pgrn. Modulating progranulin cleavage may represent a new strategy to modulate PGRN and granulin levels in disease.

Download Full-text

L1CAM promotes ovarian cancer stemness and tumor initiation via FGFR1/SRC/STAT3 signaling

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-021-02117-z ◽

2021 ◽

Vol 40 (1) ◽

Author(s):

Marco Giordano ◽

Alessandra Decio ◽

Chiara Battistini ◽

Micol Baronio ◽

Fabrizio Bianchi ◽

...

Keyword(s):

Molecular Mechanisms ◽

Genetic Manipulation ◽

Tumor Formation ◽

In Vitro Assays ◽

Tumor Initiation ◽

Loss Of Function ◽

Stat3 Signaling

Abstract Background Cancer stem cells (CSC) have been implicated in tumor progression. In ovarian carcinoma (OC), CSC drive tumor formation, dissemination and recurrence, as well as drug resistance, thus contributing to the high death-to-incidence ratio of this disease. However, the molecular basis of such a pathogenic role of ovarian CSC (OCSC) has been elucidated only to a limited extent. In this context, the functional contribution of the L1 cell adhesion molecule (L1CAM) to OC stemness remains elusive. Methods The expression of L1CAM was investigated in patient-derived OCSC. The genetic manipulation of L1CAM in OC cells provided gain and loss-of-function models that were then employed in cell biological assays as well as in vivo tumorigenesis experiments to assess the role of L1CAM in OC cell stemness and in OCSC-driven tumor initiation. We applied antibody-mediated neutralization to investigate L1CAM druggability. Biochemical approaches were then combined with functional in vitro assays to study the molecular mechanisms underlying the functional role of L1CAM in OCSC. Results We report that L1CAM is upregulated in patient-derived OCSC. Functional studies showed that L1CAM promotes several stemness-related properties in OC cells, including sphere formation, tumor initiation and chemoresistance. These activities were repressed by an L1CAM-neutralizing antibody, pointing to L1CAM as a druggable target. Mechanistically, L1CAM interacted with and activated fibroblast growth factor receptor-1 (FGFR1), which in turn induced the SRC-mediated activation of STAT3. The inhibition of STAT3 prevented L1CAM-dependent OC stemness and tumor initiation. Conclusions Our study implicate L1CAM in the tumorigenic function of OCSC and point to the L1CAM/FGFR1/SRC/STAT3 signaling pathway as a novel driver of OC stemness. We also provide evidence that targeting this pathway can contribute to OC eradication.

Download Full-text

KIF15 supports spermatogenesis via its effects on Sertoli cell microtubule, actin, vimentin, and septin cytoskeletons

Endocrinology ◽

10.1210/endocr/bqab010 ◽

2021 ◽

Vol 162 (4) ◽

Author(s):

Siwen Wu ◽

Lixiu Lv ◽

Linxi Li ◽

Lingling Wang ◽

Baiping Mao ◽

...

Keyword(s):

Basement Membrane ◽

Sertoli Cell ◽

Cell Function ◽

Seminiferous Epithelium ◽

Loss Of Function ◽

Specific Expression ◽

Specific Distribution ◽

Regulatory Effects

Abstract Throughout spermatogenesis, cellular cargoes including haploid spermatids are required to be transported across the seminiferous epithelium, either toward the microtubule (MT) plus (+) end near the basement membrane at stage V, or to the MT minus (−) end near the tubule lumen at stages VI to VIII of the epithelial cycle. Furthermore, preleptotene spermatocytes, differentiated from type B spermatogonia, are transported across the Sertoli cell blood-testis barrier (BTB) to enter the adluminal compartment. Few studies, however, have been conducted to explore the function of MT-dependent motor proteins to support spermatid transport during spermiogenesis. Herein, we examined the role of MT-dependent and microtubule plus (+) end–directed motor protein kinesin 15 (KIF15) in the testis. KIF15 displayed a stage-specific expression across the seminiferous epithelium, associated with MTs, and appeared as aggregates on the MT tracks that aligned perpendicular to the basement membrane and laid across the entire epithelium. KIF15 also tightly associated with apical ectoplasmic specialization, displaying strict stage-specific distribution, apparently to support spermatid transport across the epithelium. We used a loss-of-function approach by RNAi to examine the role of KIF15 in Sertoli cell epithelium in vitro to examine its role in cytoskeletal-dependent Sertoli cell function. It was noted that KIF15 knockdown by RNAi that reduced KIF15 expression by ~70% in Sertoli cells with an established functional tight junction barrier impeded the barrier function. This effect was mediated through remarkable changes in the cytoskeletal organization of MTs, but also actin-, vimentin-, and septin-based cytoskeletons, illustrating that KIF15 exerts its regulatory effects well beyond microtubules.

Download Full-text

VE-cadherin endocytosis controls vascular integrity and patterning during development

The Journal of Cell Biology ◽

10.1083/jcb.201909081 ◽

2020 ◽

Vol 219 (5) ◽

Cited By ~ 3

Author(s):

Cynthia M. Grimsley-Myers ◽

Robin H. Isaacson ◽

Chantel M. Cadwell ◽

Jazmin Campos ◽

Marina S. Hernandes ◽

...

Keyword(s):

Mutant Mice ◽

Loss Of Function ◽

Adhesive Properties ◽

Vascular Integrity ◽

P120 Catenin ◽

Mouse Mutants ◽

Dynamic Cell ◽

And Migration

Tissue morphogenesis requires dynamic intercellular contacts that are subsequently stabilized as tissues mature. The mechanisms governing these competing adhesive properties are not fully understood. Using gain- and loss-of-function approaches, we tested the role of p120-catenin (p120) and VE-cadherin (VE-cad) endocytosis in vascular development using mouse mutants that exhibit increased (VE-cadGGG/GGG) or decreased (VE-cadDEE/DEE) internalization. VE-cadGGG/GGG mutant mice exhibited reduced VE-cad-p120 binding, reduced VE-cad levels, microvascular hemorrhaging, and decreased survival. By contrast, VE-cadDEE/DEE mutants exhibited normal vascular permeability but displayed microvascular patterning defects. Interestingly, VE-cadDEE/DEE mutant mice did not require endothelial p120, demonstrating that p120 is dispensable in the context of a stabilized cadherin. In vitro, VE-cadDEE mutant cells displayed defects in polarization and cell migration that were rescued by uncoupling VE-cadDEE from actin. These results indicate that cadherin endocytosis coordinates cell polarity and migration cues through actin remodeling. Collectively, our results indicate that regulated cadherin endocytosis is essential for both dynamic cell movements and establishment of stable tissue architecture.

Download Full-text

The Role of Methionine Aminopeptidase 2 in Lymphangiogenesis

International Journal of Molecular Sciences ◽

10.3390/ijms21145148 ◽

2020 ◽

Vol 21 (14) ◽

pp. 5148

Author(s):

Rawnaq Esa ◽

Eliana Steinberg ◽

Dvir Dror ◽

Ouri Schwob ◽

Mehrdad Khajavi ◽

...

Keyword(s):

Endothelial Cells ◽

Cell Function ◽

Loss Of Function ◽

Methionine Aminopeptidase ◽

Zebrafish Model ◽

Lymphatic Capillary ◽

Intracellular Enzyme

During the metastasis process, tumor cells invade the blood circulatory system directly from venous capillaries or indirectly via lymphatic vessels. Understanding the relative contribution of each pathway and identifying the molecular targets that affect both processes is critical for reducing cancer spread. Methionine aminopeptidase 2 (MetAp2) is an intracellular enzyme known to modulate angiogenesis. In this study, we investigated the additional role of MetAp2 in lymphangiogenesis. A histological staining of tumors from human breast-cancer donors was performed in order to detect the level and the localization of MetAp2 and lymphatic capillaries. The basal enzymatic level and activity in vascular and lymphatic endothelial cells were compared, followed by loss of function studies determining the role of MetAp2 in lymphangiogenesis in vitro and in vivo. The results from the histological analyses of the tumor tissues revealed a high MetAp2 expression, with detectable sites of co-localization with lymphatic capillaries. We showed slightly reduced levels of the MetAp2 enzyme and MetAp2 mRNA expression and activity in primary lymphatic cells when compared to the vascular endothelial cells. The genetic and biochemical manipulation of MetAp2 confirmed the dual activity of the enzyme in both vascular and lymphatic remodulation in cell function assays and in a zebrafish model. We found that cancer-related lymphangiogenesis is inhibited in murine models following MetAp2 inhibition treatment. Taken together, our study provides an indication that MetAp2 is a significant contributor to lymphangiogenesis and carries a dual role in both vascular and lymphatic capillary formation. Our data suggests that MetAp2 inhibitors can be effectively used as anti-metastatic broad-spectrum drugs.

Download Full-text