Publications by authors named "Michael Munson"

Objective: Intimate partner violence (IPV) is highly prevalent among transgender and gender diverse (TGD) adults. Integrated theories of minority stress and alcohol-related IPV suggest minority stress risk and protective factors should interact with alcohol use to predict IPV, although this has never been examined in TGD adults. Thus, we examined the synergistic influence of alcohol use, minority stress, and TGD community connectedness on IPV perpetration among TGD adults.

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Efficient and targeted delivery of therapeutic agents remains a bottleneck in modern medicine. Here, biochemical engineering approaches to advance the repurposing of extracellular vesicles (EVs) as drug delivery vehicles are explored. Targeting ligands such as the sugar GalNAc are displayed on the surface of EVs using a HaloTag-fused to a protein anchor that is enriched on engineered EVs.

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Cells use noncanonical autophagy, also called conjugation of ATG8 to single membranes (CASM), to label damaged intracellular compartments with ubiquitin-like ATG8 family proteins in order to signal danger caused by pathogens or toxic compounds. CASM relies on E3 complexes to sense membrane damage, but so far, only the mechanism to activate ATG16L1-containing E3 complexes, associated with proton gradient loss, has been described. Here, we show that TECPR1-containing E3 complexes are key mediators of CASM in cells treated with a variety of pharmacological drugs, including clinically relevant nanoparticles, transfection reagents, antihistamines, lysosomotropic compounds, and detergents.

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Here, we aimed to chemically modify PAMAM dendrimers using lysine as a site-selective anchor for successfully delivering mRNA while maintaining a low toxicity profile. PAMAM dendrimers were multi-functionalised by amidation reactions in a regioselective, quantitative and stepwise manner with carefully selected property-modifying surface groups. Alternatively, novel lysine-based dendrimers were prepared in the same manner with the aim to unlock their potential in gene delivery.

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During autophagy, cytosolic cargo is sequestered into double-membrane vesicles called autophagosomes. The contributions of specific lipids, such as cholesterol, to the membranes that form the autophagosome, remain to be fully characterized. Here, we demonstrate that short term cholesterol depletion leads to a rapid induction of autophagy and a corresponding increase in autophagy initiation events.

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Article Synopsis
  • Oligonucleotides (ONs) have therapeutic potential, but their effectiveness is limited by their inability to escape endosomes and reach cellular targets.
  • The study introduces two new endosomolytic compounds that enhance the delivery of splice-switching oligonucleotides (SSOs) by causing endosomal membrane rupture and promoting SSO release into the cytosol.
  • The research uses advanced microscopy and functional assays to demonstrate that these compounds can improve the functional activity of ONs and suggest their promising role as fast-acting transfection reagents in antisense therapies.
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In recent years, there has been an increasing interest in designing delivery systems to enhance the efficacy of RNA-based therapeutics. Here, we have synthesized copolymers comprised of dimethylaminoethyl methacrylate (DMAEMA) or diethylaminoethyl methacrylate (DEAEMA) copolymerized with alkyl methacrylate monomers ranging from 2 to 12 carbons, and developed a high throughput workflow for rapid investigation of their applicability for mRNA delivery. The structure activity relationship revealed that the mRNA encapsulation efficiency is improved by increasing the cationic density and use of shorter alkyl side chains (2-6 carbons).

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Article Synopsis
  • Mitochondria removal is crucial for cell health, with recent research focusing on a specific type of mitophagy regulated by the E3 ligase PRKN, while the understanding of "housekeeping" mitophagy is limited.
  • Using iron chelation to promote PRKN-independent mitophagy, researchers identified two kinases—GAK and PRKCD—that positively regulate this process.
  • PRKCD helps recruit other proteins essential for mitophagy, while GAK alters mitochondrial structures, and inhibiting either kinase disrupts normal mitophagy, highlighting their importance.
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The mechanisms involved in programmed or damage-induced removal of mitochondria by mitophagy remains elusive. Here, we have screened for regulators of PRKN-independent mitophagy using an siRNA library targeting 197 proteins containing lipid interacting domains. We identify Cyclin G-associated kinase (GAK) and Protein Kinase C Delta (PRKCD) as regulators of PRKN-independent mitophagy, with both being dispensable for PRKN-dependent mitophagy and starvation-induced autophagy.

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The aim of this study was to evaluate the impact of discharge destination on diabetes-related limb salvage surgery outcomes post-hospitalisation. This was a single-centre, observational, descriptive study of 175 subjects with diabetes who underwent limb salvage surgery of a minor foot amputation or wide incision and debridement for an acutely infected diabetic foot ulcer (DFU). Comparisons were made between subjects discharged home vs a skilled nursing facility (SNF) for 12 months postoperatively.

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RNA-based therapies have great potential to treat many undruggable human diseases. However, their efficacy, in particular for mRNA, remains hampered by poor cellular delivery and limited endosomal escape. Development and optimisation of delivery vectors, such as lipid nanoparticles (LNPs), are impeded by limited screening methods to probe the intracellular processing of LNPs in sufficient detail.

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Aims: Patients with diabetes, including those with foot complications, are at highest risk for severe outcomes during the COVID-19 pandemic. Diabetic foot ulcers (DFU) present additional challenges given their superimposed risk for severe infections and amputations. The main objectives were to develop a triage algorithm to effectively risk-stratify all DFUs for potential complications, complying with social distancing regulations, preserving personal protective equipment, and to assess feasibility of virtual care for DFU.

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Inactivation of the endosomal sorting complex required for transport (ESCRT) machinery has been reported to cause autophagic defects, but the exact functions of ESCRT proteins in macroautophagy/autophagy remain incompletely understood. Using live-cell fluorescence microscopy we found that the filament-forming ESCRT-III subunit CHMP4B was recruited transiently to nascent autophagosomes during starvation-induced autophagy and mitophagy, with residence times of about 1 and 2 min, respectively. Correlative light microscopy and electron tomography revealed CHMP4B recruitment at a late step in mitophagosome formation.

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Objective: Hyperglycemia leads to increase advanced glycation end products (AGEs) in patients with type 1 and type 2 diabetes. Subsequently, formation of AGEs can cause increased plantar fascial thickness (PFT), an imaging feature of plantar fasciitis (PF). This study evaluates the prevalence of PF in a contemporary cohort of type 1 diabetes and type 2 diabetes patients managed according to current standards, compared to patients without diabetes.

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Eukaryotic cells have the capacity to degrade intracellular components through a lysosomal degradation pathway called macroautophagy (henceforth referred to as autophagy) in which superfluous or damaged cytosolic entities are engulfed and separated from the rest of the cell constituents into double membraned vesicles known as autophagosomes. Autophagosomes then fuse with endosomes and lysosomes, where cargo is broken down into basic building blocks that are released to the cytoplasm for the cell to reuse. Autophagic degradation can target either cytoplasmic material in bulk (non-selective autophagy) or particular cargo in what is called selective autophagy.

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Trafficking of mammalian ATG9A between the Golgi apparatus, endosomes and peripheral ATG9A compartments is important for autophagosome biogenesis. Here, we show that the membrane remodelling protein SNX18, previously identified as a positive regulator of autophagy, regulates ATG9A trafficking from recycling endosomes. ATG9A is recruited to SNX18-induced tubules generated from recycling endosomes and accumulates in juxtanuclear recycling endosomes in cells lacking SNX18.

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Purpose: Complications from diabetes mellitus including major lower extremity amputation may have significant impact on a patient's mortality. This study determined what impact the addition of a limb salvage and diabetic foot program involving podiatry had at an academic institution over 16years by analyzing high-low amputation ratio data.

Methods: The high-low amputation ratio in the diabetic population who underwent non-traumatic amputation of the lower extremity was retrospectively evaluated at an academic institution via cohort discovery of the electronic medical record and analysis of billing over 16years.

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VPS34 is the only class III phosphatidylinositol-3-kinase (PI3K) in mammalian cells and produces the vast majority of cellular phosphatidylinositol-3-phosphate [PI(3)P]. PI(3)P is a key signalling lipid that plays many membrane trafficking roles in processes such as endocytosis and autophagy. VPS34 is a key cellular regulator, loss of function can have catastrophic effects and is embryonic lethal (Zhou , 2011).

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The lipid Phosphatidylinositol-3-phosphate [PtdIns3P or PI(3)P] plays many membrane trafficking roles and is primarily produced by the Class III PI3K, VPS34. Determining the level of cellular PI(3)P however can be complex. Extraction of cellular lipids by methanol/chloroform can struggle to separate and identify distinct phospholipid species.

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Autophagic turnover of mitochondria, termed mitophagy, is proposed to be an essential quality-control (QC) mechanism of pathophysiological relevance in mammals. However, if and how mitophagy proceeds within specific cellular subtypes in vivo remains unclear, largely because of a lack of tractable tools and models. To address this, we have developed "mito-QC," a transgenic mouse with a pH-sensitive fluorescent mitochondrial signal.

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Background: We sought to study the impact of foot complications on 10-year mortality independent of other demographic and biological risk factors in a racially and socioeconomically diverse managed-care population with access to high-quality medical care.

Methods: We studied 6,992 patients with diabetes in Translating Research Into Action for Diabetes (TRIAD), a prospective observational study of diabetes care in managed care. Foot complications were assessed using administrative claims data.

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Charcot neuropathic osteoarthropathy (CN) is a rare disease (NIDDK, NIH Summary Report Charcot Workshop, 2008) that causes significant morbidity and mortality for affected patients. The disease can result in severe deformities of the foot and ankle that contribute to the development of ulcerations and amputations. Medical advances have failed to find ways to stop the progression of the disease.

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A key point in starvation-induced autophagy occurs at the end of the process, where lysosomes are regenerated from autolysosomes through a pathway termed autophagic lysosome reformation (ALR). ALR occurs when autolysosomal MTOR becomes reactivated by amino acids derived from the autophagic delivery of protein cargo. This activation not only turns off autophagosome formation but also leads to reformation of lysosomes, ready for the next round of autophagy, through a series of events involving autolysosomal tubulation.

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The mammalian or mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a ubiquitously expressed multimeric protein kinase complex that integrates nutrient and growth factor signals for the co-ordinated regulation of cellular metabolism and cell growth. Herein, we demonstrate that suppressing the cellular activity of glycogen synthase kinase-3 (GSK3), by use of pharmacological inhibitors or shRNA-mediated gene silencing, results in substantial reduction in amino acid (AA)-regulated mTORC1-directed signalling, as assessed by phosphorylation of multiple downstream mTORC1 targets. We show that GSK3 regulates mTORC1 activity through its ability to phosphorylate the mTOR-associated scaffold protein raptor (regulatory-associated protein of mTOR) on Ser(859).

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Lysosomes are essential organelles that function to degrade and recycle unwanted, damaged and toxic biological components. Lysosomes also act as signalling platforms in activating the nutrient-sensing kinase mTOR. mTOR regulates cellular growth, but it also helps to maintain lysosome identity by initiating lysosomal tubulation through a process termed autophagosome-lysosome reformation (ALR).

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