Browsing by Author "Blackburn, Jonathan M"

Now showing 1 - 9 of 9
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    Comprehensive definition of Ser/Thr/Tyr phosphorylation in mycobacteria: towards understanding reprogramming of normal macrophage function by pathogenic mycobacteria
    (2018) Nakedi, Kehilwe Confidence; Blackburn, Jonathan M; Da Cruz Soares, Nelson
    Mycobacterium tuberculosis, the causative agent for the disease Tuberculosis, is a serious public health problem that is responsible for 1.6 million deaths each year. The WHO’s recent report on Tuberculosis estimates that a third of the world’s population is latently infected with the bacteria, and, of those, 10% will progress to active disease. M. tuberculosis is a successful pathogen mainly due to its ability to adapt and survive in changing environments. It can survive a dormant state with limited metabolic activity during latent infection, while also being able to escape the macrophage and disseminate into active disease. Efforts to eradicate the disease must be based on understanding the biology of this organism, and the mechanisms it uses to infect, colonize, and evade the immune system. Understanding the behaviour of pathogenic mycobacteria in the macrophage is also important to the discovery of new drug targets. In this thesis, we employed state of the art mass spectrometry techniques, which allowed us to unpack the biology of this bacterium in different growth environments and expand our understanding of the mechanisms it employs to adapt and survive. We investigated protein regulation by the process of phosphorylation, through sensory kinases, which add a phosphate group to a protein of interest, thereby regulating its function. First, we interrogated the phosphoproteomic landscape between M. bovis BCG and M. smegmatis to explain how differential protein regulation results in the differences between slow and fast growth of mycobacteria. Second, we focused on Protein Kinase G (PknG), which plays an important role in bacterial survival by blocking phagosome/lysosome fusion. We identified the in vivo physiological substrates of this kinase in actively growing M.bovis BCG culture. Our results revealed that this kinase is a regulator of protein synthesis. We then examined the mechanisms of survival in murine RAW 246.7 macrophages mediated by PknG, using M. bovis BCG reference strain and PknG knock-out mutant. Our results indicated strong evidence that pathogenic mycobacteria disrupt the macrophagic cytoskeleton, through phosphorylation of proteins that are involved in cytoskeleton rearrangement. These results explain the strategies that pathogenic mycobacteria employ mediated by PknG to block phagosome-lysosome fusion and evade the host immune system and survive for prolonged periods in the macrophages. The findings of this thesis contribute to our understanding of the physiology of pathogenic mycobacteria and their interaction with the host.
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    Correction to: Microbial function and genital inflammation in young South African women at high risk of HIV infection
    (2022-03-09) Alisoltani, Arghavan; Manhanzva, Monalisa T; Potgieter, Matthys; Balle, Christina; Bell, Liam; Ross, Elizabeth; Iranzadeh, Arash; du Plessis, Michelle; Radzey, Nina; McDonald, Zac; Calder, Bridget; Allali, Imane; Mulder, Nicola; Dabee, Smritee; Barnabas, Shaun; Gamieldien, Hoyam; Godzik, Adam; Blackburn, Jonathan M; Tabb, David L; Bekker, Linda-Gail; Jaspan, Heather B; Passmore, Jo-Ann S; Masson, Lindi
    Correction to: Microbiome 8, 165 (2020) https://doi.org/10.1186/s40168-020-00932-8
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    A network analysis based proteomic and transcriptomic investigation into HIV-Tat induced neuronal dysfunction and the neuroprotective effect of lithium
    (2016) Ganief, Tariq Ahmad; Blackburn, Jonathan M
    HIV-associated neurocognitive disorders (HAND) affect up to 70% of HIV positive individuals and are the leading cause of dementia in patients under 40 years. Despite this, the molecular mechanisms involved in the onset of HAND are not well understood. Among a number of plausible etiological agents of HAND, HIV-Tat has been shown to be neurotoxic in vitro and in vivo, but the basis of its induced neuronal dysregulation remains relatively poorly characterised, giving rise to various competing theories. This thesis describes differential, quantitative proteomic analyses of HIV-Tat-treated neuronal cells in vitro, the goal being to gain deeper insight into the underlying molecular basis of this HIV-Tat-mediated dysregulation, as well as to potentially inform better patient treatments in the future. To achieve this goal, deep, quantitative proteomic analysis of HIV-Tat treated SILAC-labelled SH-SY5Y neuroblastoma cells was carried out, alongside transcriptomic analysis of the same system in which 3077 proteins were identified and quantified with 407 proteins and 1074 genes being differentially expressed. Subsequently, label-free proteomics analysis was used to study the ability of lithium - a proposed new treatment for HAND - to suppress the HIV-Tat induced dysregulated molecular phenotype in SH-SY5Y cells in which 3757 were identified and quantified with 360 and 531 being significantly differentially expressed in HIV-Tat and HIV-Tat + lithium treated cells, respectively.
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    Novel urinary and serological markers of prostate cancer using proteomics techniques: an important tool for early cancer diagnosis and treatment monitoring
    (2016) Adeola, Henry Ademola; Zerbini, Luiz F; Blackburn, Jonathan M
    In Africa, Prostate cancer (PCa) is the most frequently diagnosed solid organ tumour in males and use of prostate specific antigen (PSA) is presently fraught with diagnostic inaccuracies. Not least, in a multi-ethnic society like South Africa, proteome differences between African, Caucasian and Mixed-Ancestry PCa patients are largely unknown. Hence, discovery and validation of affordable, non-invasive and reliable diagnostic biomarkers of PCa would expand the frontiers of PCa management. We have employed two high-throughput proteomics technologies to identify novel urine- and blood-based biomarkers for early diagnosis and treatment monitoring of prostate cancer in a South African cohort as well as elucidate proteome differences in patients from our heterogeneous cohort. We compared the urinary proteomes of PCa, Benign Prostatic Hyperplasia (BPH), disease controls comprising patients with other uropathies (DC) and normal healthy controls (NC) both by pooling and individual discovery shotgun proteomic assessment on a nano-Liquid chromatography (nLC) coupled Hybrid Quadrupole-Orbitrap Mass Spectrometer platform. In-silico verification of identified biomarkers was performed using the Human Protein Atlas (HPA) as well as SRMAtlas; and verified potential biomarkers were experimentally prevalidated using a targeted parallel reaction monitoring (PRM) proteomics approach. Further, we employed the CT100+ antigen microarray platform to assess the differential humoral antibody response of PCa, DC and BPH patients in our cohort to a panel of 123 tumour-associated cancer antigens. Candidate antigen biomarkers were analyzed for ethnic group variation in our cohort and potential cancer diagnostic and immunotherapeutic inferences were drawn. Using these approaches, we identified 5595 and 9991 non-redundant peptides from the pooled and individual experiments respectively. While nine proteins demonstrated ethnic trend, 37 and 73 proteins were differentially expressed by pooled and individual analysis respectively. All 32 verified biomarkers were prevalidated with parallel reaction monitoring. Good PRM signals for 12 top ranking biomarker was observed, including PSA and prostatic acid phosphatase. We also identified 41 potential diagnostic and immunotherapeutic antigen biomarkers. Proteogenomic functional pathway analyses of differentially expressed antigens showed similar enrichments of biologic processes. We identified herein novel urinary and blood-based potential diagnostic biomarkers and immunotherapeutic targets of PCa in a South African PCa Cohort using multiple proteomics approaches.
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    PMA: Protein Microarray Analyser, a user-friendly tool for data processing and normalization
    (BioMed Central, 2018-02-27) Da Gama Duarte, Jessica; Goosen, Ryan W; Lawry, Peter J; Blackburn, Jonathan M
    Objective Protein microarrays provide a high-throughput platform to measure protein interactions and associated functions, and can aid in the discovery of cancer biomarkers. The resulting protein microarray data can however be subject to systematic bias and noise, thus requiring a robust data processing, normalization and analysis pipeline to ensure high quality and robust results. To date, a comprehensive data processing pipeline is yet to be developed. Furthermore, a lack of analysis consistency is evident amongst different research groups, thereby impeding collaborative data consolidation and comparison. Thus, we sought to develop an accessible data processing tool using methods that are generalizable to the protein microarray field and which can be adapted to individual array layouts with minimal software engineering expertise. Results We developed an improved version of a previously developed pipeline of protein microarray data processing and implemented it as an open source software tool, with particular focus on widening its use and applicability. The Protein Microarray Analyser software presented here includes the following tools: (1) neighbourhood background correction, (2) net intensity correction, (3) user-defined noise threshold, (4) user-defined CV threshold amongst replicates and (5) assay controls, (6) composite ‘pin-to-pin’ normalization amongst sub-arrays, and (7) ‘array-to-array’ normalization amongst whole arrays.
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    Profiling medulloblastoma and juvenile pilocytic astrocytoma brain tumours in a South African paediatric cohort
    (2017) Nair, Omesan; Figaji, Anthony; Blackburn, Jonathan M
    Brain tumours in children are one of the most challenging diseases to treat, and so outcomes are variable and often lacking. There are currently no reliable data of presentation of disease, the spectrum of tumours treated, how these are treated, and what the outcomes are for children in South Africa, and certainly no molecular biology data. In this respect, this thesis investigated the two commonest types of childhood brain tumour, the highly malignant Medulloblastoma (MB) and the generally less aggressive Juvenile Pilocytic Astrocytoma (JPA) with relation to their molecular biology and their clinical correlates to begin to address this gap and build capacity for further molecular-based studies in an African context. The study design in this thesis takes a systematic approach and is structured into MB and JPA biochemical characterisation followed by 4 studies of their respective proteomic profiles. The study design involved creating appropriate patient cohorts and determining sample characteristics for interpretation of results. The statistical power achieved in this thesis showed a minimum of 2-fold difference for a power greater than 0.8 in each case. Proteomic clustering was used to validate or delineate any discrepancies in subtype assignments for MB. Molecular profiles together with proteomic data of MB and JPA cases in this thesis provide evidence for some novel molecular pathways, proteins and peptides associated with pathogenesis. This work therefore provides extensive data that is hypothesis generating for further studies that could build upon molecular understanding in a South African and larger African context.
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    Proteomic studies on patient responses to chemotherapy, radiotherapy and immunotherapy in cancers
    (2015) Duarte, Jessica Da Gama; Blackburn, Jonathan M
    There is increasing evidence that the aberrant expression of cancer-testis (CT) antigens - a family of ca. 150 proteins that are both autoimmunogenic and mainly restricted to tumours in various types of human cancers - makes them attractive immunotherapy targets, as well as possible cancer diagnostic markers. We carried out a retrospective serological study of primary and secondary autoimmune responses of various cohorts of cancer patients prior to and/or following a variety of distinct treatments (chemotherapy, radiotherapy and immunotherapy), using a large number of archived human serum samples. Our goals were to develop and validate a novel cancer-testis and -associated antigen microarray platform and to then explore its utility and general applicability in the cancer immunology field. In addition, we sought to cross-correlate our protein microarray data from specific cohorts with in vitro T-cell re-stimulation assays for a selected subset of patients. Furthermore, as a means of determining the biological significance of our protein microarray data, we also collected clinical patient data where possible. The underlying hypothesis of our study was that there were measurable differences in autoantibody repertoires towards tumour-specific and -associated antigens between pre- and post-treated cancer patient samples (using various trial therapies), potentially augmented by prior chemo- or radiotherapy, which would correlate with likelihood of response of individual patients to a given therapeutic treatment - including those treatments that aim to generate T-cell responses - and which would also correlate with the nature and extent of individual patient responses to treatment.
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    Quantitative Profiling of Colorectal Cancer-Associated Bacteria Reveals Associations between Fusobacterium spp., Enterotoxigenic Bacteroides fragilis (ETBF) and Clinicopathological Features of Colorectal Cancer
    (Public Library of Science, 2015) Viljoen, Katie S; Dakshinamurthy, Amirtha; Goldberg, Paul; Blackburn, Jonathan M
    Various studies have presented clinical or in vitro evidence linking bacteria to colorectal cancer, but these bacteria have not previously been concurrently quantified by qPCR in a single cohort. We quantify these bacteria ( Fusobacterium spp ., Streptococcus gallolyticus , Enterococcus faecalis , Enterotoxigenic Bacteroides fragilis (ETBF), Enteropathogenic Escherichia coli (EPEC), and afaC- or pks-positive E . coli ) in paired tumour and normal tissue samples from 55 colorectal cancer patients. We further investigate the relationship between a) the presence and b) the level of colonisation of each bacterial species with site and stage of disease, age, gender, ethnicity and MSI-status. With the exception of S . gallolyticus , we detected all bacteria profiled here in both tumour and normal samples at varying frequencies. ETBF (FDR = 0.001 and 0.002 for normal and tumour samples) and afaC -positive E . coli (FDR = 0.03, normal samples) were significantly enriched in the colon compared to the rectum. ETBF (FDR = 0.04 and 0.002 for normal and tumour samples, respectively) and Fusobacterium spp. (FDR = 0.03 tumour samples) levels were significantly higher in late stage (III/IV) colorectal cancers. Fusobacterium was by far the most common bacteria detected, occurring in 82% and 81% of paired tumour and normal samples. Fusobacterium was also the only bacterium that was significantly higher in tumour compared to normal samples (p = 6e-5). We also identified significant associations between high-level colonisation by Fusobacterium and MSI-H (FDR = 0.05), age (FDR = 0.03) or pks -positive E . coli (FDR = 0.01). Furthermore, we exclusively identified atypical EPEC in our cohort, which has not been previously reported in association with colorectal cancer. By quantifying colorectal cancer-associated bacteria across a single cohort, we uncovered inter- and intra-individual patterns of colonization not previously recognized, as well as important associations with clinicopathological features, especially in the case of Fusobacterium and ETBF.
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    Unravelling the molecular mechanisms of HIV associated neurocognitive disorders through mass spectrometry-based proteomics
    (2016) Gurwitz, Kim Tamara; Blackburn, Jonathan M; Soares, Nelson
    A significant proportion of human immunodeficiency virus type 1 (HIV)-positive individuals are affected by the cognitive, motor and behavioural dysfunction that characterises HIV associated neurocognitive disorders. While the molecular aetiology of this important HIV complication remains largely uncharacterised, HIV transactivator of transcription (HIV-Tat) has been identified as a plausible aetiological cause. Here we have used mass spectrometry-based discovery proteomics to identify the quantitative, cell-wide changes that occur when non-transformed, differentiated human neurons are treated with HIV-Tat over time, as a novel cell culture model representing the initial progression of HIV associated neurocognitive disorders, and as a means to identify putative biomarkers for the illness. We found that our stem cell-based model system displayed morphological and functional neuronal properties and using a Q-Exactive mass spectrometer, we identified over 4000 protein groups (FDR < 0.01) in this system with 131,118 and 45 protein groups differentially expressed at 6, 24 and 48 hours post treatment, respectively. We found changes to the gene expression machinery (nucleic acid binding proteins), which suggests that HIV-Tat is involved in preparing the host cell for altered transcriptional and translational activity. We also found cytoskeletal dysregulation in response to HIV-Tat treatment. The 24-hour time point of the time course experiment was largely corroborated with a repeat experiment. A repeat of the entire time course experiment at a lower cell confluence showed that the effect of HIV-Tat treatment to the gene expression machinery was unchanged by cell confluence, while the effect to cytoskeletal proteins upon HIV-Tat treatment was present, but less prominent, in lower cell confluence samples. We hypothesise that the gene-expression-machinery effect may be a biphasic response. We further hypothesise that cytoskeletal dysregulation may form part of the molecular mechanism responsible for synaptic injury - as the cytoskeleton is crucial for synapse development and maintenance - and may contribute to memory impairment in HIV associated neurocognitive disorder patients.