Biology subjects

Fredrickson, G.

Publications and source records attributed to Fredrickson, G..

7 recordsLinked to original sources

bioRxiv2026

Cell-type resolved prenylomics in mouse liver enabled by a low-input proteomics workflow

Protein prenylation is a lipid modification crucial for membrane association and cellular signaling, but its dysregulation is linked to cancer and neurodegenerative diseases. Typical "prenylomic" workflows rely on metabolic labeling with bio-orthogonal isoprenoid probes followed by streptavidin enrichment; however, they generally require milligram-scale protein inputs (15-25 million cells), preventing the study of scarce primary or sorted cell populations. To overcome this limitation, we developed a highly sensitive, low-input prenylomic workflow combining optimized streptavidin enrichment with library-free data-independent acquisition (DIA) mass spectrometry. This method enables deep prenylomic coverage from just 50 ug of total protein input, a 20-fold reduction compared to prior methods. In COS7 cells, this workflow identified 91 prenylated protein groups, outperforming TMT-DDA methods that yielded 81 groups from 2 mg of input, using the same bio-orthogonal probe for enrichment, while coefficient of variation (CV) analysis demonstrated superior quantitative precision and reproducibility. Applied in vivo in mice following subcutaneous probe administration, the low-input methodology overcame sample input limitations to profile cell-type-specific prenylomes from dissociated liver tissue, identifying 29 enriched prenylated proteins in hepatocytes and 18 in macrophages. Pathway enrichment analysis showed that the identified proteins are consistent with the biology of the respective cell-types. This robust methodology significantly lowers the sample threshold for lipid proteomics, expanding the accessibility of prenylomics to limited primary cells and sorted tissue populations to study cell-type-specific prenylation dynamics in disease contexts.

biochemistry↗

bioRxiv2026

ATGL-catalyzed lipid catabolism promotes DNA repair

An imbalance of DNA damage over DNA repair contributes to the genomic instability that drives aging and numerous age-related diseases. While numerous DNA repair mechanisms have been elucidated over decades of study, little is known about the contribution of metabolism to genomic stability. We report that adipose triglyceride lipase (ATGL), a lipolytic enzyme, promotes DNA repair. We show that lipid droplets (LDs) accumulate in response to DNA damage and that inhibition of LD biogenesis before genotoxic stress increases the persistence of DNA damage. Overexpression of ATGL, which increases lipolysis, reduces DNA damage following etoposide and ionizing radiation, thereby promoting genomic stability. Further, ATGL expression prior to DNA damage attenuates the long-term consequences of DNA damage, reducing senescence and enhancing viability. Mechanistically, ATGL promotes double-strand break repair via NHEJ and HR to mitigate DNA damage. Overall, these studies reveal a novel role for LDs and their proteins in DNA damage and repair, thereby unveiling a mechanism by which lipid metabolism contributes to genomic stability.

biochemistry↗

bioRxiv2024

Macrophage-derived CCL24 promotes fibrosis and worsens cardiac dysfunction during heart failure

Inflammation is a significant risk factor and contributes to cardiovascular disease by driving both adaptive and maladaptive processes. Macrophages are the most abundant immune cells in the heart and play an important role in the remodeling of cardiac tissue. We have previously shown an overall protective function of resident cardiac macrophages after pressure-overloaded injury. However, a subpopulation of resident macrophages also expresses high levels of the profibrotic CC motif chemokine ligand 24 (CCL24), suggesting a dichotomous role in pressure overload-induced cardiac remodeling. Here, we report that following transverse aortic constriction CCL24 knockout (CCL24 KO) mice have improved systolic function, cardiac wall enlargement, as well as increased myocyte surface area and hypertrophy, suggesting that CCL24 disrupts compensatory hypertrophy. TAC-operated CCL24 KO mice also displayed reduced fibrosis and diminished expression of fibrotic genes, implying a pro-fibrotic role for CCL24. Indeed, CCL24 induced the proliferation and activation of primary mouse fibroblasts in a process that required CCR3, the sole G protein-coupled receptor for CCL24. Correspondingly, selective ablation of CCR3 in fibroblasts improved cardiac function and ameliorated fibrosis following pressure overload. Administration of a CCL24 blocking antibody or a CCR3 antagonist both improved cardiac function in pressure-overloaded mice, highlighting the CCL24-CCR3 axis as a potential therapeutic target for heart failure. Finally, CCL24 deficiency improved cardiac function and ameliorated fibrosis during physiological aging. Overall, these results show that macrophage-derived CCL24 aggravates fibrosis via the CCR3 receptor, leading to impaired cardiac function in acute and chronic heart failure.

immunology↗

bioRxiv2023

Pyruvate Oxidation Sustains B Cell Antigen-Specific Activation to Exacerbate MASH

B cells play a crucial role in the pathogenesis of metabolic dysfunction-associated steatohepatitis (MASH), a severe form of steatotic liver disease that if persistent can lead to cirrhosis, liver failure, and cancer. Chronic inflammation and fibrosis are key features of MASH that determine disease progression and outcomes. Recent advances have revealed that pathogenic B cell-derived cytokines and antibodies promote the development of MASH. However, the mechanisms through which B cells promote fibrosis and the metabolic adaptations underlying their pathogenic responses remain unclear. Here, we report that a subset of mature B cells with heightened cytokine responses accumulate in the liver and promote inflammation in MASH. To meet the increased energetic demand of effector responses, B cells increase their ATP production via oxidative phosphorylation (OXPHOS) fueled by pyruvate oxidation in a B cell receptor (BCR)-specific manner. Blocking pyruvate oxidation completely abrogated the inflammatory capacity of MASH B cells. Accordingly, the restriction of the BCR led to MASH attenuation, including reductions in steatosis, hepatic inflammation, and fibrosis. Mechanistically, BCR restriction decreased B cell maturation, activation, and effector responses in the liver, accompanied by decreased T cell- and macrophage-mediated inflammation. Notably, attenuated liver fibrosis in BCR-restricted mice was associated with lower IgG production and decreased expression of Fc-gamma receptors on hepatic stellate cells. Together, these findings indicate a key role for B cell antigen-specific responses in promoting steatosis, inflammation, and fibrosis during MASH.

physiology↗

bioRxiv2023

Hepatic lipid-associated macrophages mediate the protective effects of bariatric surgery against NASH

For patients with obesity and metabolic syndrome, bariatric procedures such as vertical sleeve gastrectomy (VSG) have a clear benefit in ameliorating metabolic dysfunction-associated steatohepatitis (MASH). While the effects of bariatric surgeries have been mainly attributed to nutrient restriction and malabsorption, whether immuno-modulatory mechanisms are involved remains unclear. Here we report that VSG ameliorates MASH progression in a weight loss- independent manner. Single-cell RNA sequencing revealed that hepatic lipid-associated macrophages (LAMs) expressing the triggering receptor expressed on myeloid cells 2 (TREM2) increase their lysosomal activity and repress inflammation in response to VSG. Remarkably, TREM2 deficiency in mice ablates the reparative effects of VSG, suggesting that TREM2 is required for MASH resolution. Mechanistically, TREM2 prevents the inflammatory activation of macrophages and is required for their efferocytotic function. Overall, our findings indicate that bariatric surgery improves MASH through a reparative process driven by hepatic LAMs, providing insights into the mechanisms of disease reversal that may result in new therapies and improved surgical interventions.

physiology↗

bioRxiv2023

Dysfunctional T Follicular Helper Cells Cause Intestinal and Hepatic Inflammation in NASH

Nonalcoholic steatohepatitis (NASH), characterized by hepatic inflammation and cellular damage, is the most severe form of nonalcoholic fatty liver disease and the fastest-growing indication for a liver transplant. The intestinal immune system is a central modulator of local and systemic inflammation. In particular, Peyers patches (PPs) contain T follicular helper (Tfh) cells that support germinal center (GC) responses required for the generation of high-affinity intestinal IgA and the maintenance of intestinal homeostasis. However, our understanding of the mechanisms regulating mucosal immunity during the pathogenesis of NASH is incomplete. Here, using a preclinical mouse model that resembles the key features of human disease, we discovered an essential role for Tfh cells in the pathogenesis of NASH. We have found that mice fed a high-fat high-carbohydrate (HFHC) diet have an inflamed intestinal microenvironment, characterized by enlarged PPs with an expansion of Tfh cells. Surprisingly, the Tfh cells in the PPs of NASH mice showed evidence of dysfunction, along with defective GC responses and reduced IgA+ B cells. Tfh-deficient mice fed the HFHC diet showed compromised intestinal permeability, increased hepatic inflammation, and aggravated NASH, suggesting a fundamental role for Tfh cells in maintaining gut-liver homeostasis. Mechanistically, HFHC diet feeding leads to an aberrant increase in the expression of the transcription factor KLF2 in Tfh cells which inhibits its function. Thus, transgenic mice with reduced KLF2 expression in CD4 T cells displayed improved Tfh cell function and ameliorated NASH, including hepatic steatosis, inflammation, and fibrosis after HFHC feeding. Overall, these findings highlight Tfh cells as key intestinal immune cells involved in the regulation of inflammation in the gut-liver axis during NASH.

immunology↗

bioRxiv2022

Trem2 Promotes Foamy Macrophage Lipid Uptake and Survival in Atherosclerosis

Atherosclerotic plaque formation is driven by the continued expansion of cholesterol loaded foamy macrophages within the arterial intima. Foamy macrophages are primarily derived from newly recruited monocytes, but factors regulating monocyte specification toward foamy macrophage differentiation and prolonged survival in plaque remain poorly understood. We used trajectory analysis of integrated single cell RNA-seq data, along with a genome-wide CRISPR screening approach to identify Triggering Receptor Expressed on Myeloid Cells 2 (Trem2) as a candidate regulator for foamy macrophage specification. Loss of Trem2 led to a reduced ability of foamy macrophages to take up additional oxidized low density lipoprotein (LDL) cholesterol in vitro. Competitive chimera experiments showed that Trem2-deficient macrophages were less competent to form foamy macrophages when competed against Trem2-sufficient macrophages in vivo. In addition, myeloid specific conditional deletion of Trem2 resulted in a dramatic attenuation of plaque progression, even when targeted in established atherosclerotic lesions. This was independent of changes in circulating inflammatory cytokines, monocyte recruitment, or serum cholesterol levels, but due to a reduction in plaque macrophage proliferation and enhanced cell death. Mechanistically, we link Trem2-deficient macrophages with an inability for cells to sense cholesterol loading and failure to upregulate efflux molecules. Accumulation of cholesterol in the endoplasmic reticulum enhanced activation of the ER-stress response that increased susceptibility for cholesterol-toxicity and cell death in foamy Trem2-deficient macrophages. Overall, this study identifies Trem2 as a regulator of foamy macrophage differentiation, atherosclerotic plaque growth, and as a putative therapeutic target for future intervention studies.

immunology↗