Biology subjects

Hiller, K.

Publications and source records attributed to Hiller, K..

7 recordsLinked to original sources

bioRxiv2023

Branched chain amino acid synthesis is coupled to TOR activation early in the cell cycle in yeast

How cells coordinate their metabolism with division determines the rate of cell proliferation. Dynamic patterns of metabolite synthesis during the cell cycle are unexplored. We report the first isotope tracing analysis in synchronous, growing budding yeast cells. Synthesis of leucine, a branched-chain amino acid (BCAA), increased through the G1 phase of the cell cycle, peaking later during DNA replication. Cells lacking Bat1, a mitochondrial aminotransferase that synthesizes BCAAs, grew slower, were smaller, and were delayed in the G1 phase, phenocopying cells in which the growth-promoting kinase complex TORC1 was moderately inhibited. Loss of Bat1 lowered the levels of BCAAs and reduced TORC1 activity. Exogenous provision of BCAAs to cells lacking Bat1 promoted cell division and increased TORC1 activity. In wild-type cells, TORC1 activity was dynamic in the cell cycle, starting low in early G1 but increasing later in the cell cycle. These results suggest a link between BCAA synthesis from glucose to TORC1 activation in the G1 phase of the cell cycle.

biochemistry↗

bioRxiv2022

Non-targeted metabolomics identifies erythronate accumulation in cancer cells

Using a non-targeted isotope-assisted metabolomics approach, we identified erythronate as a metabolite that accumulates in several human cancer cell lines. Erythronate has been reported to be a detoxification product derived from off-target glycolytic metabolism. We provide data supporting a possible alternative route to erythronate production involving the dephosphorylation of the pentose phosphate pathway intermediate erythrose-4-phosphate to form erythrose, followed by the oxidation of erythrose by an aldehyde dehydrogenase. Finally, we detected increased erythronate concentrations in tumors relative to adjacent normal tissues from lung cancer patients. These findings suggest the accumulation of erythronate to be an example of metabolic reprogramming in cancer cells, raising the possibility that elevated level of erythronate may serve as a biomarker of certain types of cancer.

biochemistry↗

bioRxiv2022

Evolution of resilience against heat stress in a red-tide dinoflagellate

"Red tides" are harmful algal blooms (HABs) caused by dinoflagellate microalgae that accumulate toxins lethal to other organisms, including humans via consumption of contaminated seafood. Increasingly frequent, HABs are driven by a combination of environmental factors including nutrient enrichment, particularly in warm waters. Here, we present the de novo assembled genome (~4.75 Gbp), transcriptome, proteome, and metabolome from Prorocentrum cordatum, a globally abundant, bloom-forming dinoflagellate. Using axenic algal cultures, we studied the molecular mechanisms that underpin response to temperature stress, which is relevant to current ocean warming trends. We discovered a complementary interplay between RNA editing and exon usage that regulates the expression and functional diversity of biomolecules, reflected by reduction in photosynthesis, central metabolism, and protein synthesis. Our multi-omics analyses uncover the molecular response to heat stress in an important HAB species, which is driven by complex gene structures in a large, high-G+C genome, combined with multi-level transcriptional regulation.

genomics↗

bioRxiv2022

Erythritol synthesis in human cells is elevated in response to oxidative stress and regulated by the non-oxidative pentose phosphate pathway

Erythritol is a predictive biomarker of cardiometabolic diseases and is produced from glucose metabolism through the pentose phosphate pathway (PPP). Little is known regarding the regulation of endogenous erythritol synthesis in humans. In the present study, we investigated the stimuli that promote erythritol synthesis in human cells and characterized potential points of regulation along the PPP. Human A549 lung carcinoma cells were chosen for their known ability to synthesize erythritol. A549 cells were treated with potential substrates for erythritol production, including glucose, fructose, and glycerol. Using siRNA knockdown, we assessed the necessity of enzymes G6PD, TKT, TALDO, and SORD for erythritol synthesis. We also used position-specific 13C-glucose tracers to determine whether the carbons for erythritol synthesis are derived directly from glycolysis or through the oxidative PPP. Finally, we assessed if erythritol synthesis responds to oxidative stress using chemical and genetic models. Intracellular erythritol was directly associated with media glucose concentration. In addition, siRNA knockdown of TKT or SORD inhibited erythritol synthesis, whereas siG6PD did not. Both chemically induced oxidative stress and constitutive activation of the antioxidant response transcription factor NRF2 elevated intracellular erythritol. Our findings indicate that erythritol synthesis is proportional to flux through the PPP and is regulated by non-oxidative PPP enzymes.

biochemistry↗

bioRxiv2021

IL-37 expression reduces acute and chronic neuroinflammation and rescues cognitive impairment in an Alzheimer s disease mouse model

The anti-inflammatory cytokine interleukin-37 (IL-37) is a member of the IL-1 family but not expressed in mice. We used a human IL-37 (hIL-37tg) expressing mouse, which has been subjected to various models of local and systemic inflammation as well as immunological challenges. Those studies demonstrate an immune-modulatory role of IL-37 which can be characterized as an important suppressor of innate immunity. We investigated the functions of IL-37 in the CNS and explored the effects of IL-37 on neuronal architecture and function, microglia phenotype, cytokine production and behavior after inflammatory challenge by intraperitoneal LPS-injection. Reduced spine density, activated microglia phenotype and impaired long-term potentiation (LTP) were observed in wild-type mice after LPS injection, whereas hIL-37tg mice showed no impairment. In addition, we crossed the hIL-37tg mouse with an animal model of Alzheimers disease (APP/PS1) to investigate the anti-inflammatory properties of IL-37 under chronic neuroinflammatory conditions. Our results show that IL-37 is able to limit inflammation in the brain after acute inflammatory events and prevent the loss of cognitive abilities in a mouse model of AD.

neuroscience↗

bioRxiv2021

Clostridium difficile Toxin B activates the NLRP3 inflammasome in human macrophages, demonstrating a novel regulatory mechanism for the Pyrin inflammasome

Pyrin is a cytosolic immune sensor that forms an inflammasome when bacterial virulence factors inhibit RhoA, triggering the release of inflammatory cytokines, including IL-1{beta}. Gain of function mutations in the MEFV gene encoding Pyrin cause auto-inflammatory disorders, such as familial Mediterranean fever (FMF) and Pyrin associated auto-inflammation with Neutrophilic Dermatosis (PAAND). To precisely define the role of Pyrin in detecting pathogen virulence factors in relevant human immune cells, we investigated how the Pyrin inflammasome response was initiated and regulated in monocyte-derived macrophages (hMDM) compared to human monocytes. Unlike monocytes and murine macrophages, we determined that hMDM failed to activate Pyrin in response to known Pyrin activators Clostridioides difficile (C. difficile) toxins A or B (TcdA or TcdB). In contrast, TcdB activated the NLRP3 inflammasome in hMDM. Notably, we ascertained that the Pyrin inflammasome response could be re-enabled in hMDM by prolonged priming with either LPS or type I or II interferons, and required an increase in Pyrin expression. These data demonstrate an unexpected redundancy in detecting these toxins by inflammasome sensors.

immunology↗

bioRxiv2021

Unraveling the critical growth factors for stable cultivation of (nano-sized) Micrarchaeota

Micrarchaeota are members of the archaeal DPANN superphylum. These so far poorly characterized archaea have been found to have reduced genomes and likely depend on interactions with host organisms for growth and survival. Here we report on the enrichment of the first stable co-culture of a member of the Micrarchaeota together with its host, as well as the isolation of the latter. Electron microscopic analysis suggest that growth is dependent on the physical interaction of the two organisms within a biofilm. The interaction seems to be ensured by the necessity to grow in form of a biofilm. Furthermore, transcriptomic analyses indicate a shift towards biofilm formation of the host as a result of co-cultivation. Finally, genomic, metabolomic, extracellular polymeric substance (EPSs) and lipid content analyses reveal that the Micrarchaeon symbiont relies on the acquisition of metabolites from its host and thereby provide first insights into the basis of symbiont-host interactions.

microbiology↗