Biology subjects

McCullough, A.

Publications and source records attributed to McCullough, A..

4 recordsLinked to original sources

bioRxiv2024

Chlamydia trachomatis TmeA promotes pedestal formation through N-WASP and TOCA-1 interactions

Chlamydia trachomatis (C.t.) is the causative agent of several human diseases, including the sexually transmitted infection chlamydia and eye infection trachoma. As an obligate intracellular bacterial pathogen, invasion is essential for establishing infection and subsequent pathogenesis. To facilitate invasion, C.t. secretes effector proteins through its type III secretion system (T3SS). These effectors facilitate bacterial entry by manipulating multiple pathways involved in host actin cytoskeletal regulation. Previous studies have demonstrated that the T3SS effector protein TmeA is crucial for C.t. invasion, as it recruits and activates N-WASP. This interaction leads to recruitment and activation of the Arp2/3 complex, promoting cytoskeletal rearrangements at the invasion site to facilitate C.t. uptake. In this study, we define the role of the N-WASP CRIB domain in mediating this interaction, showing that TmeA acts as a functional mimic of Cdc42 in activating N-WASP. Additionally, we identified TOCA-1 as another host protein that directly interacts with TmeA. In other bacterial pathogens, notably Enterohemorrhagic E. coli, N-WASP and TOCA-1 are hijacked to mediate pedestal formation. Using siRNA to knockdown N-WASP and TOCA-1, followed by transmission electron microscopic, we observed that both N-WASP and TOCA-1 are important for in C.t.-mediated pedestal formation. Collectively, these findings reveal a unique mechanism of TmeA-mediated invasion, where direct interactions with N-WASP and TOCA-1 facilitate pedestal formation. ImportanceChlamydia trachomatis (C.t.) is an obligate intracellular bacterial pathogen that poses a significant threat to human health, being associated with various diseases, including chlamydia-- the most prevalent bacterial sexually transmitted infection--and trachoma. While Chlamydia infections are often asymptomatic, they can lead to serious complications such as sterility, ectopic pregnancy, and increased risk of cervical and ovarian cancers. Due to its intracellular nature, host cell invasion is essential for C.t. survival. Here, we present new data detailing the binding interactions between the C.t. invasion effector protein TmeA and host cell proteins N-WASP and TOCA-1, demonstrating that both N-WASP and TOCA-1 are involved in pedestal formation during C.t. invasion. This research advances our understanding of TmeA-mediated host cell invasion, illuminating a key pathway required for C.t.-mediated pathogenesis.

microbiology↗

bioRxiv2022

Neuroimaging within the Dominantly Inherited Alzheimer's Network (DIAN): PET and MRI

The Dominantly Inherited Alzheimer Network (DIAN) Observational Study is an international collaboration studying autosomal dominant Alzheimer disease (ADAD). This rare form of Alzheimer disease (AD) is caused by mutations in the presenilin 1 (PSEN1), presenilin 2 (PSEN2), or amyloid precursor protein (APP) genes. As individuals from these families have a 50% chance of inheriting the familial mutation, this provides researchers with a well-matched cohort of carriers vs non-carriers for case-control studies. An important trait of ADAD is that the age at symptom onset is highly predictable and consistent for each specific mutation, allowing researchers to estimate an individuals point in their disease time course prior to symptom onset. Although ADAD represents only a small proportion (approximately 0.1%) of all AD cases, studying this form of AD allows researchers to investigate preclinical AD and the progression of changes that occur within the brain prior to AD symptom onset. Furthermore, the young age at symptom onset (typically 30-60 years) means age-related comorbidities are much less prevalent than in sporadic AD, thereby allowing AD pathophysiology to be studied independent of these confounds. A major goal of the DIAN Observational Study is to create a global resource for AD researchers. To that end, the current manuscript provides an overview of the DIAN magnetic resonance imaging (MRI) and positron emission tomography (PET) protocols and highlights the key imaging results of this study to date.

neuroscience↗

bioRxiv2020

C57BL6 mouse substrains demonstrate differences in susceptibility to the demyelinating effects of Cuprizone toxin

Advances in our understanding of cellular functions and phenotypes in the brain rely on technically robust experimental in vivo models with face validity towards human disease. The cuprizone toxin-induced demyelination model is widely used to investigate pathophysiological mechanisms of demyelinating and remyelinating phases of multiple sclerosis. The C57BL6 mouse is a common inbred strain used as the genetic background for genetically engineered and congenic mice. Substrains of C57BL6 mice sourced from distinct vendors are often treated as equivalent in research studies. Here, we demonstrated that an alternative dosing approach via oral gavage with a well-tolerated, lower dose of cuprizone resulted in significant differences in C57BL/6NTac (Taconic) over C57BL/6J (Jax) mice. With consistent dosing of cuprizone for 5 weeks, body weights were significantly affected in C57BL/6NTac versus C57BL/6J mice. DT-MRI showed significant demyelination in white matter regions in the C57BL/6NTac mice. Concomitantly, histology analysis illustrated increased microgliosis and proliferation in C57BL/6NTac compared with C57BL/6J mice. These observations suggest that the C57BL/6NTac substrain of C57BL6 mice is more vulnerable to cuprizone challenge. Genetic factors along with breeder source appear to influence susceptibility to cuprizone toxin. Thus, the awareness of the limitations of in vivo models in addition to informed decision making on the appropriate background substrain can greatly improve sensitivity and reproducibility of results and use for evaluating investigational therapeutics.

neuroscience↗

bioRxiv2018

An RNAi screen in human cell lines reveals conserved DNA damage repair pathways that mitigate formaldehyde sensitivity

Formaldehyde is a ubiquitous DNA damaging agent, with human exposures occuring from both exogenous and endogenous sources. Formaldehyde can also form DNA-protein crosslinks and is representative of other such DNA damaging agents including ionizing radiation, metals, aldehydes, chemotherapeutics, and cigarette smoke. In order to identify genetic determinants of cell proliferation in response to continuous formaldehyde exposure, we quantified cell proliferation after siRNA-depletion of a comprehensive array of over 300 genes representing all of the major DNA damage response pathways. Three unrelated human cell lines (SW480, U-2 OS and GM00639) were used to identify common or cell line-specific mechanisms. Four cellular pathways were determined to mitigate formaldehyde toxicity in all three cell lines: homologous recombination, double-strand break repair, ionizing radiation response, and DNA replication. Differences between cell lines were further investigated by using exome sequencing and Cancer Cell Line Encyclopedia genomic data. Our results reveal major genetic determinants of formaldehyde toxicity in human cells and provide evidence for the conservation of these formaldehyde responses between human and budding yeast.

cell biology↗