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MBio Jun 2024The injectisome encoded by pathogenicity island 2 (SPI-2) had been thought to translocate 28 effectors. Here, we used a proteomic approach to characterize the secretome...
UNLABELLED
The injectisome encoded by pathogenicity island 2 (SPI-2) had been thought to translocate 28 effectors. Here, we used a proteomic approach to characterize the secretome of a clinical strain of invasive non-typhoidal serovar Enteritidis that had been mutated to cause hyper-secretion of the SPI-2 injectisome effectors. Along with many known effectors, we discovered the novel SseM protein. is widely distributed among the five subspecies of is found in many clinically relevant serovars, and is co-transcribed with , a SPI-2 effector gene. The translocation of SseM required a functional SPI-2 injectisome. Following expression in human cells, SseM interacted with five components of the dystrophin-associated protein complex (DAPC), namely, β-2-syntrophin, utrophin/dystrophin, α-catulin, α-dystrobrevin, and β-dystrobrevin. The interaction between SseM and β-2-syntrophin and α-dystrobrevin was verified in Typhimurium-infected cells and relied on the postsynaptic density-95/discs large/zonula occludens-1 (PDZ) domain of β-2-syntrophin and a sequence corresponding to a PDZ-binding motif (PBM) in SseM. A Δ mutant strain had a small competitive advantage over the wild-type strain in the . Typhimurium/mouse model of systemic disease. This phenotype was complemented by a plasmid expressing wild-type SseM from . Typhimurium or . Enteritidis and was dependent on the PBM of SseM. Therefore, a PBM within a effector mediates interactions with the DAPC and modulates the systemic growth of bacteria in mice. Furthermore, the Δ mutant strain displayed enhanced replication in bone marrow-derived macrophages, demonstrating that SseM restrains intracellular bacterial growth to modulate virulence.
IMPORTANCE
In , the injectisome machinery encoded by pathogenicity island 2 (SPI-2) is conserved among the five subspecies and delivers proteins (effectors) into host cells, which are required for virulence. The identification and functional characterization of SPI-2 injectisome effectors advance our understanding of the interplay between and its host(s). Using an optimized method for preparing secreted proteins and a clinical isolate of the invasive non-typhoidal serovar Enteritidis strain D24359, we identified 22 known SPI-2 injectisome effectors and one new effector-SseM. SseM modulates bacterial growth during murine infection and has a sequence corresponding to a postsynaptic density-95/discs large/zonula occludens-1 (PDZ)-binding motif that is essential for interaction with the PDZ-containing host protein β-2-syntrophin and other components of the dystrophin-associated protein complex (DAPC). To our knowledge, SseM is unique among effectors in containing a functional PDZ-binding motif and is the first bacterial protein to target the DAPC.
PubMed: 38904384
DOI: 10.1128/mbio.01128-24 -
Translational Vision Science &... Jun 2024To compare gene expression changes following branch retinal vein occlusion (BRVO) in the pig with and without bevacizumab (BEV) and triamcinolone acetonide (TA).
PURPOSE
To compare gene expression changes following branch retinal vein occlusion (BRVO) in the pig with and without bevacizumab (BEV) and triamcinolone acetonide (TA).
METHODS
Photothrombotic BRVOs were created in both eyes of four groups of nine pigs (2, 6, 10, and 20 days). In each group, six pigs received intravitreal injections of BEV in one eye and TA in the fellow eye, with three pigs serving as untreated BRVO controls. Three untreated pigs served as healthy controls. Expression of mRNA of vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), dystrophin (DMD), potassium inwardly rectifying channel subfamily J member 10 protein (Kir4.1, KCNJ10), aquaporin-4 (AQP4), stromal cell-derived factor-1α (CXCL12), interleukin-6 (IL6), interleukin-8 (IL8), monocyte chemoattractant protein-1 (CCL2), intercellular adhesion molecule 1 (ICAM1), and heat shock factor 1 (HSF1) were analyzed by quantitative reverse-transcription polymerase chain reaction. Retinal VEGF protein levels were characterized by immunohistochemistry.
RESULTS
In untreated eyes, BRVO significantly increased expression of GFAP, IL8, CCL2, ICAM1, HSF1, and AQP4. Expression of VEGF, KCNJ10, and CXCL12 was significantly reduced by 6 days post-BRVO, with expression recovering to healthy control levels by day 20. Treatment with BEV or TA significantly increased VEGF, DMD, and IL6 expression compared with untreated BRVO eyes and suppressed BRVO-induced CCL2 and AQP4 upregulation, as well as recovery of KCNJ10 expression, at 10 to 20 days post-BRVO.
CONCLUSIONS
Inflammation and cellular osmohomeostasis rather than VEGF suppression appear to play important roles in BRVO-induced retinal neurodegeneration, enhanced in both BEV- and TA-treated retinas.
TRANSLATIONAL RELEVANCE
Inner retinal neurodegeneration seen in this acute model of BRVO appears to be mediated by inflammation and alterations in osmohomeostasis rather than VEGF inhibition, which may have implications for more specific treatment modalities in the acute phase of BRVO.
Topics: Animals; Bevacizumab; Triamcinolone Acetonide; Retinal Vein Occlusion; Disease Models, Animal; Angiogenesis Inhibitors; Cytokines; Intravitreal Injections; Swine; Vascular Endothelial Growth Factor A; RNA, Messenger; Glucocorticoids; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Potassium Channels, Inwardly Rectifying
PubMed: 38899953
DOI: 10.1167/tvst.13.6.13 -
International Journal of Molecular... Jun 2024Sarcospan (SSPN) is a 25-kDa transmembrane protein that is broadly expressed at the cell surface of many tissues, including, but not limited to, the myofibers from...
Sarcospan (SSPN) is a 25-kDa transmembrane protein that is broadly expressed at the cell surface of many tissues, including, but not limited to, the myofibers from skeletal and smooth muscles, cardiomyocytes, adipocytes, kidney epithelial cells, and neurons. SSPN is a core component of the dystrophin-glycoprotein complex (DGC) that links the intracellular actin cytoskeleton with the extracellular matrix. It is also associated with integrin α7β1, the predominant integrin expressed in skeletal muscle. As a tetraspanin-like protein with four transmembrane spanning domains, SSPN functions as a scaffold to facilitate protein-protein interactions at the cell membrane. Duchenne muscular dystrophy, Becker muscular dystrophy, and X-linked dilated cardiomyopathy are caused by the loss of dystrophin at the muscle cell surface and a concomitant loss of the entire DGC, including SSPN. SSPN overexpression ameliorates Duchenne muscular dystrophy in the murine model, which supports SSPN being a viable therapeutic target. Other rescue studies support SSPN as a biomarker for the proper assembly and membrane expression of the DGC. Highly specific and robust antibodies to SSPN are needed for basic research on the molecular mechanisms of SSPN rescue, pre-clinical studies, and biomarker evaluations in human samples. The development of SSPN antibodies is challenged by the presence of its four transmembrane domains and limited antigenic epitopes. To address the significant barrier presented by limited commercially available antibodies, we aimed to generate a panel of robust SSPN-specific antibodies that can serve as a resource for the research community. We created antibodies to three SSPN protein epitopes, including the intracellular N- and C-termini as well as the large extracellular loop (LEL) between transmembrane domains 3 and 4. We developed a panel of rabbit antibodies (poly- and monoclonal) against an N-terminal peptide fragment of SSPN. We used several assays to show that the rabbit antibodies recognize mouse SSPN with a high functional affinity and specificity. We developed mouse monoclonal antibodies against the C-terminal peptide and the large extracellular loop of human SSPN. These antibodies are superior to commercially available antibodies and outperform them in various applications, including immunoblotting, indirect immunofluorescence analysis, immunoprecipitation, and an ELISA. These newly developed antibodies will significantly improve the quality and ease of SSPN detection for basic and translational research.
Topics: Animals; Humans; Mice; Dystrophin; Integrins; Membrane Proteins; Muscular Dystrophy, Duchenne; Translational Research, Biomedical
PubMed: 38892308
DOI: 10.3390/ijms25116121 -
International Journal of Molecular... Jun 2024Duchenne muscular dystrophy (DMD) is an X-linked progressive disorder associated with muscle wasting and degeneration. The disease is caused by mutations in the gene... (Review)
Review
Duchenne muscular dystrophy (DMD) is an X-linked progressive disorder associated with muscle wasting and degeneration. The disease is caused by mutations in the gene that encodes dystrophin, a protein that links the cytoskeleton with cell membrane proteins. The current treatment methods aim to relieve the symptoms of the disease or partially rescue muscle functionality. However, they are insufficient to suppress disease progression. In recent years, studies have uncovered an important role for non-coding RNAs (ncRNAs) in regulating the progression of numerous diseases. ncRNAs, such as micro-RNAs (miRNAs), bind to their target messenger RNAs (mRNAs) to suppress translation. Understanding the mechanisms involving dysregulated miRNAs can improve diagnosis and suggest novel treatment methods for patients with DMD. This review presents the available evidence on the role of altered expression of miRNAs in the pathogenesis of DMD. We discuss the involvement of these molecules in the processes associated with muscle physiology and DMD-associated cardiomyopathy.
Topics: Muscular Dystrophy, Duchenne; Humans; MicroRNAs; Animals; Dystrophin; Gene Expression Regulation; Muscle, Skeletal
PubMed: 38892293
DOI: 10.3390/ijms25116108 -
Cells Jun 2024Mutations in the gene cause fatal Duchenne Muscular Dystrophy (DMD). An attractive therapeutic approach is autologous cell transplantation utilizing myogenic...
Mutations in the gene cause fatal Duchenne Muscular Dystrophy (DMD). An attractive therapeutic approach is autologous cell transplantation utilizing myogenic progenitors derived from induced pluripotent stem cells (iPSCs). Given that a significant number of DMD mutations occur between exons 45 and 55, we developed a gene knock-in approach to correct any mutations downstream of exon 44. We applied this approach to two DMD patient-specific iPSC lines carrying mutations in exons 45 and 51 and confirmed mini-DYSTROPHIN (mini-DYS) protein expression in corrected myotubes by western blot and immunofluorescence staining. Transplantation of gene-edited DMD iPSC-derived myogenic progenitors into NSG/mdx mice produced donor-derived myofibers, as shown by the dual expression of human DYSTROPHIN and LAMIN A/C. These findings further provide proof-of-concept for the use of programmable nucleases for the development of autologous iPSC-based therapy for muscular dystrophies.
Topics: Induced Pluripotent Stem Cells; Dystrophin; Humans; Muscular Dystrophy, Duchenne; CRISPR-Cas Systems; Exons; Mutation; Animals; Mice; Gene Editing; Muscle Fibers, Skeletal
PubMed: 38891104
DOI: 10.3390/cells13110972 -
Nature Communications Jun 2024Cell polarity mechanisms allow the formation of specialized membrane domains with unique protein compositions, signalling properties, and functional characteristics. By...
Cell polarity mechanisms allow the formation of specialized membrane domains with unique protein compositions, signalling properties, and functional characteristics. By analyzing the localization of potassium channels and proteins belonging to the dystrophin-associated protein complex, we reveal the existence of distinct planar-polarized membrane compartments at the surface of C. elegans muscle cells. We find that muscle polarity is controlled by a non-canonical Wnt signalling cascade involving the ligand EGL-20/Wnt, the receptor CAM-1/Ror, and the intracellular effector DSH-1/Dishevelled. Interestingly, classical planar cell polarity proteins are not required for this process. Using time-resolved protein degradation, we demonstrate that -while it is essentially in place by the end of embryogenesis- muscle polarity is a dynamic state, requiring continued presence of DSH-1 throughout post-embryonic life. Our results reveal the unsuspected complexity of the C. elegans muscle membrane and establish a genetically tractable model system to study cellular polarity and membrane compartmentalization in vivo.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Polarity; Dystrophin; Wnt Signaling Pathway; Muscles; Dishevelled Proteins; Receptor Tyrosine Kinase-like Orphan Receptors; Cell Membrane; Dystrophin-Associated Protein Complex; Wnt Proteins; Signal Transduction
PubMed: 38858388
DOI: 10.1038/s41467-024-49154-8 -
Genes, Brain, and Behavior Jun 2024Duchenne muscular dystrophy is a severe neuromuscular disorder that is caused by mutations in the DMD gene, resulting in a disruption of dystrophin production. Next to...
Duchenne muscular dystrophy is a severe neuromuscular disorder that is caused by mutations in the DMD gene, resulting in a disruption of dystrophin production. Next to dystrophin expression in the muscle, different isoforms of the protein are also expressed in the brain and lack of these isoforms leads to cognitive and behavioral deficits in patients. It remains unclear how the loss of the shorter dystrophin isoform Dp140 affects these processes. Using a variety of behavioral tests, we found that mdx and mdx mice (which lack Dp427 or Dp427 + Dp140, respectively) exhibit similar deficits in working memory, movement patterns and blood-brain barrier integrity. Neither model showed deficits in spatial learning and memory, learning flexibility, anxiety or spontaneous behavior, nor did we observe differences in aquaporin 4 and glial fibrillary acidic protein. These results indicate that in contrast to Dp427, Dp140 does not play a crucial role in processes of learning, memory and spontaneous behavior.
Topics: Animals; Mice; Blood-Brain Barrier; Muscular Dystrophy, Duchenne; Dystrophin; Male; Mice, Inbred mdx; Mice, Inbred C57BL; Aquaporin 4; Memory, Short-Term; Memory
PubMed: 38837620
DOI: 10.1111/gbb.12895 -
BioRxiv : the Preprint Server For... May 2024Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by the absence of the protein dystrophin. Dystrophin is hypothesized to work as a molecular shock...
Duchenne muscular dystrophy (DMD) is a lethal muscle disease caused by the absence of the protein dystrophin. Dystrophin is hypothesized to work as a molecular shock absorber that limits myofiber membrane damage when undergoing reversible unfolding upon muscle stretching and contraction. Utrophin is a dystrophin homologue that is under investigation as a protein replacement therapy for DMD. However, it remains uncertain whether utrophin can mechanically substitute for dystrophin. Here, we compared the mechanical properties of homologous utrophin and dystrophin fragments encoding the N terminus through spectrin repeat 3 (UtrN-R3, DysN-R3) using two operational modes of atomic force microscopy (AFM), constant speed and constant force. Our comprehensive data, including the statistics of force magnitude at which the folded domains unfold in constant speed mode and the time of unfolding statistics in constant force mode, show consistent results. We recover parameters of the energy landscape of the domains and conducted Monte Carlo simulations which corroborate the conclusions drawn from experimental data. Our results confirm that UtrN-R3 expressed in bacteria exhibits significantly lower mechanical stiffness compared to insect UtrN-R3, while the mechanical stiffness of the homologous region of dystrophin (DysN-R3) is intermediate between bacterial and insect UtrN-R3, showing greater similarity to bacterial UtrN-R3.
PubMed: 38826288
DOI: 10.1101/2024.05.18.593686 -
Frontiers in Cellular Neuroscience 2024Muscular dystrophies are a devastating class of diseases that result in a progressive loss of muscle integrity. Duchenne Muscular Dystrophy, the most prevalent form of...
Muscular dystrophies are a devastating class of diseases that result in a progressive loss of muscle integrity. Duchenne Muscular Dystrophy, the most prevalent form of Muscular Dystrophy, is due to the loss of functional Dystrophin. While much is known regarding destruction of muscle tissue in these diseases, much less is known regarding the synaptic defects that also occur in these diseases. Synaptic defects are also among the earliest hallmarks of neurodegenerative diseases, including the neuromuscular disease Amyotrophic Lateral Sclerosis (ALS). Our current study investigates synaptic defects within adult muscle tissues as well as presynaptic motor neurons in Drosophila mutants. Here we demonstrate that the progressive, age-dependent loss of flight ability in mutants is accompanied by disorganization of Neuromuscular Junctions (NMJs), including impaired localization of both presynaptic and postsynaptic markers. We show that these synaptic defects, including presynaptic defects within motor neurons, are due to the loss of Dystrophin specifically within muscles. These results should help to better understand the early synaptic defects preceding cell loss in neuromuscular disorders.
PubMed: 38812789
DOI: 10.3389/fncel.2024.1381112 -
Clinical and Translational Medicine May 2024
Topics: Humans; DNA Copy Number Variations; Female; Cohort Studies; Pregnancy; Dystrophin; Genetic Testing; Noninvasive Prenatal Testing; Prenatal Diagnosis
PubMed: 38797938
DOI: 10.1002/ctm2.1706