Biology subjects

Pereira, M. J.

Publications and source records attributed to Pereira, M. J..

6 recordsLinked to original sources

bioRxiv2026

Astrocyte-neuron mitochondrial transfer via mitoEVs supports neuronal energy metabolism and is impaired in early Alzheimer's disease

BackgroundMitochondrial dysfunction is an early and central feature of Alzheimers disease (AD). In particular, intercellular mitochondrial transfer has emerged as a mechanism of neuronal support in brain injury and neurodegeneration. However, pathways governing astrocyte-to-neuron transfer and its role in AD pathogenesis remain unknown. MethodsUsing the AppNL-G-F knock-in AD model, we combined high-resolution 4D live-cell imaging with quantitative fluorescence-based reporters to assess synaptic function and mitochondrial network dynamics in neurons and astrocytes. Direct and extracellular vesicle (EV)-restricted neuron-astrocyte co-culture systems were used to investigate bidirectional mitochondrial transfer. We performed the first in-depth structural, proteomic, and functional characterization of astrocyte-derived mitochondrial extracellular vesicles (mitoEVs) using cryo-electron microscopy, quantitative mass spectrometry, and bioenergetic analyses to define their cargo composition and metabolic effects. ResultsWe identified cell-type-specific mitochondrial remodeling in early AD, with compartmentalized synaptic energy deficits in neurons and hyperdynamic, less interconnected, yet metabolically preserved networks in astrocytes, preceding global bioenergetic decline. Bidirectional mitochondrial transfer between astrocytes and neurons, also at axonal terminals, was mediated by specialized mitoEVs but significantly reduced in the AppNL-G-Fmodel. Comprehensive proteomic and functional profiling revealed that WT astrocyte-derived mitoEVs are enriched in inner membrane and matrix proteins, supporting oxidative phosphorylation, lipid and amino acid metabolism, and redox homeostasis. In contrast, AppNL-G-F mitoEVs are selectively depleted of respiratory and fatty acid oxidation components and exhibit impaired respiration with reduced Complex IV activity. Functionally, WT mitoEVs promote mobilization of abnormal accumulation of lipid droplets in AppNL-G-Fneurons, restore fatty acid oxidation, and increase neuronal bioenergetics, including at the synapses. In contrast, disease-derived mitoEVs fail to engage these pathways. ConclusionsTogether, these findings identify mitoEV-mediated mitochondrial transfer as a glia-to-neuron metabolic pathway compromised in early AD and reveal a coordinated role for oxidative phosphorylation and fatty acid oxidation in supporting synaptic energy homeostasis.

neuroscience↗

bioRxiv2024

Streptococcus pneumoniae infection of lung epithelial cells induces internalization of surface GPI-anchored proteins through pneumolysin-mediated activation of host Rho GTPases

A return to homeostasis after infection-associated cellular injury can be accelerated by a rapid damage response. S. pneumoniae, a typically asymptomatic colonizer of the host upper respiratory tract, can cause serious and life-threatening infections when it gains access to the lungs and other organs. The cholesterol binding S. pneumoniae pore-forming toxin, pneumolysin (PLY), is central to the induction of host cell damage. Here, we first found that mouse lung infection by S. pneumoniae diminished pulmonary expression of CD73, a glycosylphosphatidylinositol anchored protein (GPI-AP) that modulates inflammation. Infection of the human pulmonary epithelial cell line H292 resulted in a PLY-dependent reduction of not only cell surface CD73, but also the population of surface expressed GPI-APs. The decrease in cell surface GPI-APs was rapid, required pore-forming activity, and could be recapitulated by purified PLY and other cholesterol binding cytolysins. In response to PLY-mediated insult, GPI-APs were not released from the surface of epithelial cells in extracellular vesicles but rather internalized by a mechanism dependent on the Rho GTPases RhoA and Cdc42. Internalization of GPI-APs was associated with lower levels of PLY-induced apoptosis and membrane permeabilization. These findings suggest that internalization of GPI-APs from epithelial cell membranes may constitute a rapid innate repair response to cell damage induced by PLY and other pore forming toxins that could help bacteria evade host defenses as many GPI-APs have roles in immunity. Author summaryStreptococcus pneumoniae causes serious infections that can result in mortality. The pore- forming toxin, pneumolysin (PLY) produced by these bacteria is important for their ability to cause disease. Understanding how the host responds to damage by this toxin can result in better treatment against infection. In this study, we found that PLY-mediated injury results in decreased expression of glycosylphosphatidylinositol anchored proteins (GPI-AP) from the cell surface by internalization. GPI-AP co-localize in cholesterol-rich areas of the membrane where PLY inserts to form pores and cells with decreased surface GPI-APs were associated with less of PLY-induced cell death and membrane permeabilization. These results suggest that GPI-AP are internalized as part of repair mechanisms activated in response to infection-induced cell injury. As many GPI-APs have important roles in the immune response, their removal from the cell may inadvertently help the bacteria establish better infection.

microbiology↗

bioRxiv2021

Lipoproteome screening of the Lyme disease agent identifies novel inhibitors of antibody-mediated complement killing

Spirochetal pathogens such as the causative agent of Lyme disease, Borrelia burgdorferi sensu lato, encode an abundance of lipoproteins; however, due in part to their evolutionary distance from more well-studied bacteria such as Proteobacteria and Firmicutes, very few spirochetal lipoproteins have assigned functions. Indeed, B. burgdorferi devotes almost 8% of its genome to lipoprotein genes and interacts with its environment primarily through the production of at least eighty surface-exposed lipoproteins throughout its tick vector-vertebrate host lifecycle (57). Several B. burgdorferi lipoproteins have been shown to serve diverse roles, such as cellular adherence or immune evasion, but the functions for most B. burgdorferi surface lipoproteins remain unknown. In this study, we developed a B. burgdorferi lipoproteome screening platform utilizing intact spirochetes that enables the identification of previously unrecognized host interactions. As spirochetal survival in the bloodstream is essential for dissemination, we targeted our screen to C1, the first component of the classical (antibody-mediated) complement pathway. We identified two high-affinity C1 interactions by the paralogous lipoproteins, ErpB and ErpQ. Using biochemical, microbiological, and biophysical approaches, we demonstrated that ErpB and ErpQ inhibit the activated forms of the C1 proteases, C1r and C1s, and represent a new mechanistic class of C1 inhibitors that protect the spirochete from antibody-mediated complement killing by allosteric regulation. In addition to identifying a novel mode of complement inhibition, our study establishes a lipoproteome screening methodology as a discovery platform for identifying direct host-pathogen interactions that are central to the pathogenesis of spirochetes, such as the Lyme disease agent. Significance StatementSpirochetal pathogens encode an abundance of lipoproteins that can provide a critical interface with the host environment. For example, Borrelia burgdorferi, the model species for spirochetal biology, must survive an enzootic life cycle defined by fluctuations between vector (tick) and vertebrate host. While B. burgdorferi expresses over eighty surface lipoproteins-- many of which likely contribute to host survival--the B. burgdorferi lipoproteome is poorly characterized. Here, we generated a platform to rapidly identify targets of B. burgdorferi surface lipoproteins and identified two orthologs that allosterically inhibit complement C1 subcomponents, conferring resistance to classical complement killing. This work expands our understanding of complement evasion mechanisms and points towards a discovery approach for identifying host-pathogen interactions that are central to spirochete pathogenesis.

microbiology↗

bioRxiv2021

Organ-specific metabolic pathways distinguish prediabetes, type 2 diabetes and normal tissues

Defects in pancreatic islets and the progression of multi-tissue insulin resistance in combination with environmental factors are the main causes of type 2 diabetes (T2D). Mass spectrometry-based proteomics of five key-metabolic tissues on a cohort of 42 multi-organ donors provided deep coverage of the proteomes of pancreatic islets, visceral adipose tissue (VAT), liver, skeletal muscle and serum. Enrichment analysis of gene ontology (GO) terms built a tissue-specific map of the chronological order of altered biological processes across healthy controls (CTRL), pre-diabetes (PD) and T2D subjects. This unique dataset allowed us to explore alterations of entire biological pathways and individual proteins in multiple tissues. We confirmed the significant decrease of the citric acid cycle and the respiratory electron transport in VAT and muscle of T2D and we provided a thorough visual representation of the complete set of downregulated proteins. Importantly, we found widespread novel alterations in relevant biological pathways including the increase in hemostasis in pancreatic islets of PD, the increase in the complement cascade in liver and pancreatic islets of PD and the elevation in cholesterol biosynthesis in liver of T2D. Overall, our findings suggest inflammatory, immune and vascular impairments in pancreatic islets as potentially causal factors of insufficient insulin production and increased glucagon levels in the early stages of T2D. In contrast alterations in lipid metabolism and mitochondrial function in the liver and VAT/muscle, respectively, became evident later in manifest T2D. This first multi-tissue proteomic map indicates the temporal order of tissue-specific metabolic dysregulation in T2D development.

cell biology↗

bioRxiv2021

Positional and Compositional Analysis of Saturated, Monounsaturated and Polyunsaturated Fatty acids in Human Adipose Tissue Triglyceride by 13C NMR

Objectives and new findings, ends with short conclusion, no referencesThe synthesis and turnover of triglyceride in adipose tissue involves enzymes with preferences for specific fatty acid classes and/or regioselectivity with regard to the fatty acid position within the glycerol moiety. The focus of the present study was to characterize both the fatty acid composition and their positional distribution in triglycerides of biopsied human subcutaneous adipose tissue using 13C NMR spectroscopy. The triglyceride sn2 position was significantly more enriched with monounsaturated fatty acids compared to the sn1,3 sites, while saturated fatty acids abundance was significantly lower in the sn2 position compared to that of sn1,3. Furthermore, the analysis revealed significant positive correlations between the total fraction of palmitoleic acid with both BMI and HOMA-IR scores. Additionally, we established that 13C NMR chemical shifts for {omega} -3 signals, centered at 31.9 ppm, provided superior resolution of the most abundant FA species, including palmitoleate, compared to the {omega} -2 signals that were used previously. 13C NMR spectroscopy reveals for the first time a highly non-homogenous distribution of FA in the glycerol sites of human adipose tissue triglyceride and that these distributions are correlated with different phenotypes such as BMI and insulin resistance.

biochemistry↗

bioRxiv2018

Intra- and inter-individual metabolic profiling highlights carnitine and lysophosphatidylcholine pathways as key molecular defects in type-2 diabetes

Type-2 diabetes (T2D) mellitus is a complex metabolic disease commonly caused by insulin resistance in several tissues. We performed a matched two-dimensional metabolic screening in tissue samples from a cohort of 43 multi-organ donors. The intra-individual analysis was assessed across five key-metabolic tissues (serum, adipose tissue, liver, pancreatic islets and muscle), and the inter-individual across three different groups reflecting T2D progression. We identified 92 metabolites differing significantly between non-diabetes and T2D subjects. Carnitines were significantly higher in liver, while lysophosphatidylcholines significantly lower in muscle and serum. An investigation of the progression to overt T2D showed that deoxycholic acid glycine conjugate was significantly higher in liver of pre-diabetes samples while additional increase in T2D was insignificant. A subset of lysophosphatidylcholines were significantly lower in the muscle of pre-diabetes subjects. Overall, the analysis of this unique dataset can increase the understanding of the metabolic interplay between organs in the development of T2D.

physiology↗