Biology subjects

Boesze-Battaglia, K.

Publications and source records attributed to Boesze-Battaglia, K..

6 recordsLinked to original sources

bioRxiv2025

Melanoregulin deficiency affects bone maintenance and lean body mass

ObjectivesStudies documented the association of melanoregulin (MREG), a cargo-sorting protein, with its binding partner, the autophagic protein, microtubule-associated protein 1 light chain 3B (LC3B) in macrophages which could affect bone physiology due to the importance of autophagy in osteoclast function. Herein we propose to test the hypothesis that MREG modulates bone remodeling. Therefore, we analyzed the Mregdsu/dsu mutant mice for bone mass, growth plate microarchitecture, and bone marrow-derived osteoclast function to understand how lack of MREG affects bone and mass at two different time points. MethodsMice femurs from wild type and MREG-/- male mice (on C57BL6)/J background) were harvested at 4 and 10 months and imaged by microcomputed tomography to assess bone mass parameters. Femurs were processed for histology by H&E and TRAP staining for assessment of osteoclast numbers. Primary bone marrow-derived macrophages from 3-week-old mice were harvested to assess osteoclast differentiation and function via TRAP, resorptive assay and Western Blot for osteoclast differentiation markers. In addition, a separate cohort of mice were analyzed via EchoMRI to characterize total lean vs. fat whole body mass. ResultsThere was a statistically significant difference in bone volume of 10-month old mice in wild type vs. MREG-/- with MREG mutation suggesting a preservative effect on phenotypical bone parameters as the mice age. A reduction in adipose tissue but an increase in osteoclast numbers was found histologically in MREG mutant femurs. Bone marrow-derived cells, however, showed reduced osteoclastic function in MREG-/-. The mutant mice presented a total lean mass significantly increased compared to wild type per EchoMRI. ConclusionsMREG deficiency seems to impact osteoclast numbers in vivo but not in vitro, although in vitro function was reduced. MREG deficiency favors lean mass preservation over fat accumulation in bones and body composition as mice age. This study provides the foundation for a more in-depth investigation of MREGs role in bone and systemic metabolism. It is possible that MREG can be a future target for new therapeutic modalities in inflammatory and metabolic bone diseases.

cell biology↗

bioRxiv2023

Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function

Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or to age-related disease triggers lipid accumulation within the RPE, on Bruchs membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (apoB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPE{Delta}Mttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor -associated cholesterol deposits and photoreceptor cell death, and loss of rod but not cone function. RPE-specific ablation of Mttp had no significant effect on plasma lipids and lipoproteins. While, apoB was decreased in the RPE, ocular retinoid concentrations remained unchanged. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but not directly involved in ocular retinoid and plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.

cell biology↗

bioRxiv2023

Aggregatibacter actinomycetemcomitans (Aa) cytolethal distending toxin (Cdt) modulates host phagocytic function.

Cytolethal distending toxins (Cdt) are a family of toxins produced by several human pathogens which infect mucocutaneous tissue and induce inflammatory disease. Human macrophages exposed to Aggregatibacter actinomycetemcomitans (Aa) Cdt respond through canonical and non-canonical inflammasome activation to stimulate cytokine release. The inflammatory response is dependent on PI3K signaling blockade via the toxins phosphatidylinositol-3,4,5-triphosphate (PIP3) phosphatase activity; converting PIP3 to phosphatidylinsoitol-3,4-diphosphate (PI3,4P2) thereby depleting PIP3 pools. Phosphoinositides, also play a critical role in phagosome trafficking, serving as binding domains for effector proteins during phagosome maturation and subsequent fusion with lysosomes. We now demonstrate that AaCdt manipulates the phosphoinositide (PI) pools of phagosome membranes and alters Rab5 association. Exposure of macrophages to AaCdt slowed phagosome maturation and decreased phago-lysosome formation, thereby compromising macrophage phagocytic function. Moreover, macrophages exposed to Cdt showed decreased bactericidal capacity leading to increase in Aggregatibacter actinomycetemcomitans survival. Thus, Cdt may contribute to increased susceptibility to bacterial infection. These studies uncover an underexplored aspect of Cdt function and provide new insight into the virulence potential of Cdt in mediating the pathogenesis of disease caused by Cdt-producing organisms such as Aa.

immunology↗

bioRxiv2023

Transcriptomic changes predict metabolic alterations in LC3 associated phagocytosis in aged mice

LC3b (Map1lc3b) plays an essential role in canonical autophagy and is one of several components of the autophagy machinery that mediates non-canonical autophagic functions. Phagosomes are often associated with lipidated LC3b, to pro-mote phagosome maturation in a process called LC3-associated phagocytosis (LAP). Specialized phagocytes such as mammary epithelial cells, retinal pigment epithelial (RPE) cells, and sertoli cells utilize LAP for optimal degradation of phagocytosed material, including debris. In the visual system, LAP is critical to maintain retinal function, lipid homeostasis and neuroprotection. In a mouse model of retinal lipid steatosis - mice lacking LC3b (LC3b-/-), we observed increased lipid deposition, metabolic dysregulation and enhanced inflammation. Herein we present a non-biased approach to determine if loss of LAP mediated processes modulate the expression of various genes related to metabolic homeostasis, lipid handling, and inflammation. A comparison of the RPE transcriptome of WT and LC3b-/- mice revealed 1533 DEGs, with ~73% upregulated and 27% down-regulated. Enriched gene ontology (GO) terms included inflammatory response (upregulated DEGs), fatty acid metabolism and vascular transport (downregulated DEGs). Gene set enrichment analysis (GSEA) identified 34 pathways; 28 were upregulated (dominated by inflammation/related pathways) and 6 were downregulated (dominated by metabolic pathways). Analysis of additional gene families identified significant differences for genes in the solute carrier family, RPE signature genes, and genes with potential role in age-related macular degeneration. These data indicate that loss of LC3b induces robust changes in the RPE transcriptome contributing to lipid dysregulation and metabolic imbalance, RPE atrophy, inflammation, and disease pathophysiology.

biochemistry↗

bioRxiv2019

Aggregatibacter actinomycetemcomitans LtxA hijacks endocytic trafficking pathways in human lymphocytes

Leukotoxin (LtxA) from oral pathogen Aggregatibacter actinomycetemcomitans is a secreted membrane-damaging protein. LtxA is internalized by {beta}2 integrin LFA-1 (CD11a/CD18) expressing leukocytes and ultimately causes cell death; however toxin localization in the host cell is poorly understood and these studies fill this void. We investigated LtxA trafficking using multi-fluor confocal imaging, flow cytometry and Rab5 knockdown in human T lymphocyte Jurkat cells. Planar lipid bilayers were used to characterize LtxA pore-forming activity at different pH. Our results demonstrate that LtxA/LFA-1 complex gains an access to the cytosol of Jurkat cells without evidence of plasma membrane damage utilizing dynamin-dependent and clathrin-independent mechanism. Upon internalization LtxA follows the LFA-1 endocytic trafficking pathways as identified by co-localization experiments with endosomal and lysosomal markers (Rab5, Rab11A, Rab7, and Lamp2) and CD11a. Knockdown of Rab5a resulted in loss of susceptibility of Jurkat cells to LtxA cytotoxicity suggesting that late events of LtxA endocytic trafficking are required for toxicity. The toxin trafficking via the degradation endocytic pathway may culminate in delivery of the protein to lysosomes or its accumulation in Rab11A-dependent recycling endosomes. The ability of LtxA to form pores at acidic pH may result in permeabilization of the endosomal and lysosomal membranes.

microbiology↗

bioRxiv2019

Peroxisome turnover and diurnal modulation of antioxidant activity in retinal pigment epithelia utilizes microtubule-associated protein 1 light chain 3B

The retinal pigment epithelium (RPE) supports the outer retina through essential roles in the retinoid the visual cycle, nutrient supply, ion exchange and waste removal. Each day the RPE removes the oldest [~]10% of photoreceptor outer segments through phagocytic uptake, which peaks in a synchronous burst following light onset. Impaired degradation of phagocytosed OS material by the RPE can lead to toxic accumulation of lipids, oxidative tissue damage, inflammation and cell death. OSs are rich in very long chain fatty acids which are preferentially catabolized in peroxisomes. Despite the importance of lipid degradation in RPE function, the regulation of peroxisome number and activity relative to diurnal OS ingestion is relatively unexplored. Using immunohistochemistry, immunoblotting and catalase activity assays, we investigated peroxisome abundance and activity at 6 am, 7 am (at lights on), 8 am, and 3 pm, in WT mice and mice lacking microtubule-associated protein 1 light chain 3B (LC3B), that have impaired degradation of phagosomes. We found that catalase activity, but not protein expression, is 50% higher in the morning compared with 3 pm, in RPE of WT but not LC3B-/- mice. Surprisingly, we found that peroxisome abundance was stable during the day, however numbers are elevated overall in LC3B-/- mice, implicating LC3B in autophagic organelle turnover in RPE. Our data suggest that RPE peroxisome function is regulated in coordination with phagocytosis, possibly through direct enzyme regulation, and may serve to prepare RPE peroxisomes for daily surges in ingested lipid-rich OS.

biochemistry↗