Biology subjects

Dam, J.

Publications and source records attributed to Dam, J..

5 recordsLinked to original sources

bioRxiv2025

Structural basis and physiological significance of non-canonical Gs coupling to the prototypical Gi-coupled melatonin MT1 receptor

G protein-coupled receptors (GPCRs) transduce extracellular stimuli into intracellular signals by coupling to various heterotrimeric G proteins. However, the rules governing G protein preference remain largely elusive. MT1 and MT2 are prototypical Gi/o-coupled GPCRs responding to melatonin, a hormone secreted in a circadian manner. We show here that MT1, but not MT2, couples also to Gs proteins in vitro and activates the Gs/cAMP pathway upon long-term melatonin exposure in vivo, mimicking physiological dawn conditions. We solved the cryo-electron microscopy structure of the melatonin-MT1-Gs complex at 3.0[A] resolution, which revealed a strikingly distinct binding mode compared to the MT1-Gi complex. The third intracellular loop of MT1 emerges as a key stabilizer for Gs coupling, a feature previously unrecognized. This is the first solved receptor-Gs complex of a primary Gi-coupled GPCRs, providing new structural and functional insights into G protein selectivity and circadian switch of G protein coupling.

molecular biology↗

bioRxiv2025

BRET-Based Mitochondrial Subcompartment Localization Biosensors

The last decade has witnessed a marked increase in interest in mitochondria, whose dysfunction leads to the development of multiple diseases. Mitochondria are unique as they are highly compartmentalized organelles that are composed of two closely apposed membranes and whose biological function relies on the precise localization of nuclear-encoded proteins in distinct mitochondrial subcompartments. Here we developed a series of bioluminescence resonance energy transfer (BRET)-based localization biosensors to monitor the precise localization of proteins in different mitochondrial subcompartments (outer and inner membrane, intermembrane space at the inner boundary membrane, crista lumen and matrix) with a high spatial resolution (1-10 nm). These biosensors detected the correct localization and orientation of TOM20, TOM22, VDAC1, MICU1, ATP5F1C, OTC, and SIRT2/3 proteins in their respective subcompartments, as well as the translocation of BAX and Drp1 from the cytosol to mitochondria in intact cells. The localization sensors provide non-invasive tools to monitor protein localization and translocation to mitochondria in real-time with nanometer resolution in intact cells submitted to various stressors.

cell biology↗

bioRxiv2025

Novel mouse model reveals neurodevelopmental origin of PMM2-CDG brain pathology

Congenital disorders of glycosylation (CDG) are a group of neurogenetic conditions resulting from disruptions in the cellular glycosylation machinery. The majority of CDG patients have compound heterozygous pathogenic variants in the phosphomannomutase 2 (PMM2) gene. Individuals with PMM2-CDG exhibit multi-systemic symptoms, prominently featuring neurological deficits with nearly all patients exhibiting cerebellar hypoplasia and ataxia. To overcome embryonic lethality caused by whole body knock-out of Pmm2 and mimic patient-related compound heterozygous pathogenic variants, we paired a Pmm2 flox allele (Pmm2fl) with a catalytically inactive knock-in allele (Pmm2R137H), commonly present in PMM2-CDG patients. Mice with post-mitotic loss of PMM2 from neurons or astrocytes are indistinguishable from unaffected littermates, including in a broad battery of neurological assessments. In contrast, removal of PMM2 from embryonic neural precursor cells leads to cerebellar hypoplasia, ataxia, seizures, and early lethality. Comprehensive multi-omics profiling, including metabolomics, glycomics, single-cell transcriptomics, proteomics, and glycoproteomics, reveal widespread molecular disturbances throughout the brain, with the cerebellum showing the most pronounced disruption. These findings highlight the heightened dependency of the developing cerebellum on intact N-glycosylation, aligning with clinical observations in PMM2-CDG patients. Importantly, glycoproteomic alterations identified in our mouse model are corroborated in PMM2-CDG patient post-mortem cerebellar tissue, underscoring the translational relevance of our findings and implicating impaired synaptic transmission as a key pathogenic mechanism.

neuroscience↗

bioRxiv2022

Novel repertoire of tau biosensors to monitor pathological tau transformation and seeding activity in living cells

Aggregates of the tau protein are a well-known hallmark of several neurodegenerative diseases, collectively referred as tauopathies, including frontal temporal dementia and Alzheimers disease (AD). Monitoring the transformation process of tau from physiological monomers into pathological oligomers or aggregates in a high-throughput, quantitative manner and in a cellular context is still a major challenge in the field. Identifying molecules able to interfere with those processes is of high therapeutic interest. Here, we developed a series of inter- and intramolecular tau biosensors based on the highly sensitive Nanoluciferase (Nluc) binary technology (NanoBiT) able to monitor the pathological conformational change and self-interaction of tau in living cells. Our repertoire of tau biosensors reliably report i. molecular proximity of physiological full-length tau at microtubules; ii. changes in tau conformation and self-interaction associated with tau phosphorylation, as well as iii. tau interaction induced by seeds of recombinant tau or from mouse brain lysates of a mouse model of tau pathology. By comparing biosensors comprising different tau forms (i.e. full-length or short fragments, wild-type or the disease-associated tau(P301L) variant) further insights in the tau transformation process are obtained. Proof-of-concept data for the high-throughput suitability and identification of molecules interfering with the pathological tau transformation processes are presented. This novel repertoire of tau biosensors is aimed to boost the disclosure of molecular mechanisms underlying pathological tau transformation in living cells and to discover new drug candidates for tau-related neurodegenerative diseases.

cell biology↗

bioRxiv2022

Melatonin drugs inhibit SARS-CoV-2 entry into the brain and virus-induced damage of cerebral small vessels

COVID-19 is a complex disease with short- and long-term respiratory, inflammatory and neurological symptoms that are triggered by the infection with SARS-CoV-2. Invasion of the brain by SARS-CoV-2 has been observed in humans and is postulated to be involved in post COVID condition. Brain infection is particularly pronounced in the K18-hACE2 mouse model of COVID-19. Here, we show that treatment of K18-hACE2 mice with melatonin and two melatonin-derived marketed drugs, agomelatine and ramelteon, prevent SARS-CoV-2 entry in the brain thereby reducing virus-induced damage of small cerebral vessels, immune cell infiltration and brain inflammation. Brain entry of SARS-CoV-2 through endothelial cells is prevented by melatonin through allosteric binding to human angiotensin-converting enzyme 2 (ACE2), which interferes with the cell entry receptor function of ACE2 for SARS-CoV-2. Our findings open new perspectives for the repurposing of melatonergic drugs in the prevention of brain infection by SARS-CoV-2 and COVID-19-related long-term neurological symptoms.

pharmacology and toxicology↗