Biology subjects

Graetz, L.

Publications and source records attributed to Graetz, L..

9 recordsLinked to original sources

bioRxiv2026

NLRP3 activators disrupt the endocytic AP2 complex and plasma membrane signaling

Organellar perturbations are linked to NLRP3 inflammasome activation, however, it remains unclear whether unrelated agonists converge on a common upstream pathway. Here, we traced intracellular organelle and protein movements by differential ultracentrifugation combined with mass spectrometry-based proteomics. We show that NLRP3 activators uniformly disrupt the endocytic Adaptor Protein 2 (AP2) complex, whereas other subcellular rearrangements are stimulus-specific. We discovered Dynasore as a K-efflux-independent NLRP3 activator that engages this signaling node irrespective of endocytosis inhibition. Pharmacological and genetic perturbation of AP2 renders cells unresponsive to extracellular cues, blunting GPCR signaling, cAMP production, and chemotaxis, thereby enforcing a frozen signaling state that propagates NLRP3 inflammasome activation. Collectively, our study reveals a common surveillance checkpoint linking impaired plasma membrane signaling to the execution of inflammation and cell death. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/707400v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@178eb1dorg.highwire.dtl.DTLVardef@193cb02org.highwire.dtl.DTLVardef@1f50080org.highwire.dtl.DTLVardef@1f3e3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

Characterising the contribution of auditory and somatosensory inputs to TMS-evoked potentials following stimulation of prefrontal, premotor and parietal cortex

Transcranial magnetic stimulation (TMS) results in a series of evoked potentials (TEPs) in electroencephalography (EEG) recordings. However, it remains unclear whether these responses reflect neural activity resulting from transcranial stimulation of the cortex, or from the sensory experiences of TMS. Across three experiments (total n = 135), we recorded EEG activity following TMS to the dorsolateral prefrontal cortex, premotor cortex, and parietal cortex as well as a sensory control condition (stimulation of the shoulder or electrical stimulation of the scalp with a click sound). We found that TEPs showed a stereotypical frontocentral N100/P200 complex following TMS of all cortical sites and control conditions, regardless of TMS intensity or the type of sensory control. In contrast, earlier TEPs (<60 ms) showed site-specific characteristics which were largest at the site of stimulation. Self-reported sensory experiences differed across sites, with prefrontal stimulation resulting in stronger auditory (click sound perception) and somatosensory input (scalp muscle twitch, discomfort) than premotor or parietal stimulation, a pattern that was reflected in the amplitude of later (N100/P200), but not earlier (<60 ms) TEP peak amplitudes. Later TEPs were also larger in individuals who experienced stronger click sound perception and, to a lesser extent, TMS-evoked scalp muscle twitches. Increasing click sound perception by removing auditory masking increased N100/P200 amplitudes without altering earlier peaks, an effect which was more prominent at sites with more successful masking. Together, these findings suggest that the frontocentral N100/P200 complex represents a generalised sensory response resulting from TMS-related auditory and somatosensory input. In contrast, early TEP peaks likely reflect activity resulting from transcranial stimulation of the cortex. The results have important implications for designing and interpreting TEP studies, especially when comparing TEPs between stimulation sites and participant groups showing differences in sensory experiences following TMS.

neuroscience↗

bioRxiv2023

Age-Related Differences in Alpha Power for Distractor Inhibition During Visual Working Memory

As visual working memory (WM) is limited in capacity, it is important to direct neural resources towards task-relevant information and away from task-irrelevant information. Neural oscillations in the alpha frequency band (8-12 Hz) have been suggested to play a role in the inhibition of distracting information during WM retention in younger adults, but it is unclear if alpha power modulation also supports distractor inhibition in older adults. Here, we recorded electroencephalography (EEG) while 24 younger (aged 18-35) and 24 older (aged 60-86) adults completed a modified delay match-to-sample task in which distractors of varying strength appeared during the retention period. We found: (1) strong distractors impaired WM performance compared with weak and no distractors in both age groups, but there were no age-differences in WM performance; (2) while younger adults demonstrated significant increases in alpha power prior to the onset of the distractor in all conditions, decreases in alpha power were seen in all distractor conditions in older adults; (3) there was no difference in alpha power between the strong and no distractor conditions; and (4) alpha power in anticipation of the distractor was only associated with task performance in younger adults. Our results suggest that younger adults, but not older adults, modulate alpha power in anticipation of distractors during the visual WM retention period.

neuroscience↗

bioRxiv2022

WNT stimulation induced conformational dynamics in the Frizzled-Dishevelled interaction

Frizzleds (FZD1-10) are G protein-coupled receptors containing an extracellular cysteine-rich-domain (CRD) that presents the orthosteric binding site of the 19 mammalian WNTs, the endogenous agonists of FZDs. FZDs signal via a diverse set of effector proteins, of which Dishevelled (DVL1-3) is the most well studied and which acts as a hub for several FZD-mediated signaling pathways. However, the mechanistic details of how FZD-DVL interaction mediate pathway initiation and provide pathway selectivity remain an enigma. Here, we use bioluminescence resonance energy transfer-based assays employing Venus-tagged DVL2 together with NanoLuciferase-tagged FZD5 to investigate the WNT-3A- and WNT-5A-induced dynamics of the FZD-DVL interaction. Our biophysical assessment suggests that the ligand-induced BRET changes over time originate from conformational dynamics in the FZD5-DVL2 complex rather than recruitment dynamics of DVL2 to FZD5. Thus, we suggest that extracellular agonist and intracellular transducers could cooperate with each other through allosteric interaction with FZDs in a ternary complex reminiscent of that of classical GPCRs. One Sentence SummaryAnalysis of the interaction of FZD5 and DVL2 uncovers WNT-induced conformational dynamics of a WNT-FZD5-DVL2 complex.

pharmacology and toxicology↗

bioRxiv2022

Receptor levels determine binding affinity of WNT-3A to Frizzled 7 in a colorectal cancer model

WNT binding to Frizzleds (FZD) is a crucial step that leads to the initiation of signalling cascades governing multiple processes during embryonic development, stem cell regulation and adult tissue homeostasis. Recent efforts have enabled us to shed light on WNT-FZD pharmacology in overexpressed HEK293 cell systems. However, it is important to assess ligand binding at endogenous receptor levels as there might be differential binding behaviour in a native environment. Here, we focus on one FZD paralogue: FZD7, and study its interactions with WNT-3A in a CRISPR-Cas9-edited SW480 colorectal cancer model. SW480 cells were CRISPR-Cas9-edited to insert a HiBiT-tag on the N-terminus of FZD7, preserving the native signal peptide. Subsequently, these cells were used to study eGFP-WNT-3A association to endogenous and overexpressed HiBiT-FZD7 using NanoBiT/BRET to measure ligand binding and quantification of NanoBiT-emitted luminescence to assess receptor internalization. eGFP-WNT-3A bound to endogenous HiBiT-FZD7 with significantly higher kon and with lower Kd than to overexpressed receptors. Importantly, as the fluorescent probe is an agonist, experiments performed in cell lysates demonstrated that eGFP-WNT-3A/HiBiT-FZD7 binding assessment is not altered by receptor internalization. In conclusion, binding affinities of eGFP-WNT-3A to HiBiT-FZD7 decreased with increasing receptor concentrations suggesting that HiBiT-FZD7 overexpression fails to recapitulate ligand binding behaviour in a (patho-)physiologically relevant context where endogenous receptor expression levels are lower.

pharmacology and toxicology↗

bioRxiv2021

Age differences in aperiodic neural activity measured with resting EEG

Previous research using electroencephalography (EEG) and magnetoencephalography (MEG) has shown that neural oscillatory activity within the alpha band (8-12 Hz) becomes slower and lower in amplitude with advanced age. However, most studies have focused on quantifying age-related differences in periodic oscillatory activity with little consideration of the influence of aperiodic activity on these measures. The aim of this study was to investigate age differences in aperiodic activity inherent in the resting EEG signal. We assessed aperiodic activity in 85 healthy younger adults (mean age: 22.2 years, SD: 3.9, age range: 18-35, 37 male) and 92 healthy older adults (mean age: 66.1 years, SD: 8.2, age range 50-86, 53 male) by fitting the 1/f-like background activity evident in EEG power spectra using the fitting oscillations & one over f (FOOOF) toolbox. Across the scalp, the aperiodic exponent and offset were smaller in older compared to younger participants, reflecting a flatter 1/f-like slope and a downward broadband shift in the power spectra with age. Before correcting for aperiodic activity, older adults showed slower peak alpha frequency and reduced peak alpha power relative to younger adults. After correcting for aperiodic activity, peak alpha frequency remained slower in older adults; however, peak alpha power no longer differed statistically between age groups. The large sample size utilized in this study, as well as the depth of analysis, provides further evidence that the aperiodic component of the resting EEG signal is altered with aging and should be considered when investigating neural oscillatory activity.

neuroscience↗

bioRxiv2020

The role of alpha power in the suppression of anticipated distractors during verbal working memory

As working memory (WM) is limited in capacity, it is important to direct neural resources towards processing task-relevant information while ignoring distractors. Neural oscillations in the alpha frequency band (8-12 Hz) have been suggested to play a role in the inhibition of task-irrelevant information during WM, although results are mixed, possibly due to differences in the type of WM task employed. Here, we examined the role of alpha power in inhibition of anticipated distractors of varying strength using a modified Sternberg task where the encoding and retention periods were temporally separated. We recorded EEG while 20 young adults completed the task and found: 1) slower reaction times in strong distractor trials compared to weak distractor trials; 2) increased alpha power in posterior regions from baseline prior to presentation of a distractor regardless of condition; and 3) no differences in alpha power between strong and weak distractor conditions. Our results suggest that parieto-occipital alpha power is increased prior to a distractor. However we could not find evidence that alpha power is further modulated by distractor strength.

neuroscience↗

bioRxiv2019

Load-dependent modulation of alpha oscillations during working memory encoding and retention in young and older adults

Working memory (WM) is vulnerable to age-related decline, particularly under high loads. Visual alpha oscillations contribute to WM performance in younger adults, and although alpha decreases in power and frequency with age, it is unclear if alpha activity supports WM in older adults. We recorded electroencephalography (EEG) while 24 younger (aged 18-35 years) and 30 older (aged 50-86) adults performed a modified Sternberg task with varying load conditions. Older adults demonstrated slower reaction times at all loads, but there were no significant age differences in accuracy. Regardless of age, alpha power decreased, and alpha frequency increased with load during encoding, and the magnitude of alpha suppression during retention was larger at higher loads. While alpha power during retention was lower than fixation in older, but not younger adults, the relative change from fixation was not significantly different between age groups. Individual differences in alpha power did not predict performance for either age groups or at any WM loads. Future research should elaborate the functional significance of alpha power and frequency changes that accompany WM performance in cognitive ageing.

neuroscience↗

bioRxiv2018

Characterization of young and old adult brains: An EEG functional connectivity analysis

Brain connectivity studies have reported that functional networks change with older age. We aim to (1) investigate whether electroencephalography (EEG) data can be used to distinguish between individual functional networks of young and old adults; and (2) identify the functional connections that contribute to this classification. Two eyes-open resting-state EEG recording sessions with 64 electrodes for each of 22 younger adults (19-37 years) and 22 older adults (63-85 years) were conducted. For each session, imaginary coherence matrices in theta, alpha, beta and gamma bands were computed. A range of machine learning classification methods were utilized to distinguish younger and older adult brains. A support vector machine (SVM) classifier was 94% accurate in classifying the brains by age group. We report decreased functional connectivity with older age in theta, alpha and gamma bands, and increased connectivity with older age in beta band. Most connections involving frontal, temporal, and parietal electrodes, and approximately two-thirds of connections involving occipital electrodes, showed decreased connectivity with older age. Just over half of the connections involving central electrodes showed increased connectivity with older age. Functional connections showing decreased strength with older age had significantly longer electrode-to-electrode distance than those that increased with older age. Most of the connections used by the classifier to distinguish participants by age group belonged to the alpha band. Findings suggest a decrease in connectivity in key networks and frequency bands associated with attention and awareness, and an increase in connectivity of the sensorimotor functional networks with ageing during a resting state.

neuroscience↗