Biology subjects

Koller, A.

Publications and source records attributed to Koller, A..

4 recordsLinked to original sources

bioRxiv2026

Aberrant FICD-mediated AMPylation drives α-Synuclein pathology and overall protein dyshomeostasis in dopaminergic neurons in Parkinson's disease

BackgroundFilamentation induced by cAMP domain-containing protein (FICD) is an endoplasmic reticulum (ER)-resident adenylyltransferase that catalyzes protein AMPylation, a post-translational modification. Although FICD-mediated AMPylation has been linked to the fine-tuning of proteostasis and neuronal integrity, its role in neurodegenerative diseases characterized by protein dyshomeostasis remains unclear. Parkinsons disease (PD) is defined by dopaminergic neurodegeneration and aggregation of -synuclein (aSyn) as a consequence of impaired protein homeostasis. We therefore investigated whether dysregulated FICD-mediated AMPylation contributes to PD pathogenesis. MethodsWe combined analyses of human post-mortem PD brain tissue with complementary models, including midbrain dopaminergic neurons derived from human induced pluripotent stem cells (hiPSCs) of a PD patient carrying an SNCA gene duplication and its isogenic gene dosage-corrected control line, transgenic mouse models of synucleinopathy, and an aSyn-overexpressing H4 neuroglioma cell model. Genetic and pharmacological modulation of FICD activity was integrated with multi-proteomic approaches, including chemical proteomics-based AMPylation profiling, stable isotope labelling with amino acids in cell culture-based global protein turnover analysis, and whole-proteome profiling to identify AMPylation-associated molecular pathways. ResultsFICD was preferentially expressed in dopaminergic neurons and was upregulated in SNCA duplication PD patient-derived neurons, as well as in the basal ganglia of PD post-mortem brains and synucleinopathy mice. Despite this overall increase, the proportion of FICD-expressing dopaminergic neurons was reduced under PD conditions, suggesting selective vulnerability of dopaminergic neurons to FICD. Mechanistically, FICD selectively AMPylated lysosomal proteins, thereby linking AMPylation to the regulation of degradative pathways. Moreover, hyperactivation of FICD-induced AMPylation triggered ER stress, impaired lysosomal function, reduced protein turnover, and ultimately promoted aSyn aggregation and apoptotic cell death. Importantly, pharmacological inhibition of AMPylation reversed aSyn pathology and neurite degeneration in PD patient-derived neurons. ConclusionsWe identify the pathological relevance of FICD-mediated AMPylation in PD-related neurodegeneration and its contribution to aSyn aggregation through a bidirectional interplay with aSyn pathology. Our findings support FICD-mediated AMPylation as a defining molecular switch regulating intracellular protein homeostasis in PD and highlight the FICD-AMPylation pathway as a potential therapeutic target for restoring aSyn pathology and mitigating disease progression.

neuroscience↗

bioRxiv2025

AMPylation regulates PLD3 processing.

The 5-3 exonuclease phospholipase D3 (PLD3) is a single-pass transmembrane protein undergoing sequential post-translational modifications (PTM) by N-glycosylation, AMPylation and proteolytic cleavage. The substrates of PLD3 5-3 exonuclease activity are single-stranded DNAs and RNAs, which act as ligands for Toll-like receptors (TLRs) and trigger a downstream pro-inflammatory response. Although PLD3 has primarily been studied in immune cells, recent findings indicate its enrichment in neurons, where it plays a role in regulating axonal fitness in Alzheimers disease (AD). However, the regulatory mechanisms governing the proteolytic processing of PLD3 into its catalytically active soluble form and its functional roles in both immune and neuronal cells remain unclear. Here, we describe the functional implications of PLD3 AMPylation, its direct interaction with the protein adenylyltransferase FICD, and changes in PLD3 processing in Parkinsons disease (PD) patient-derived neurons. We identified PLD3 AMPylation sites within the proteins soluble region and show that mutation of these sites lead to loss of PLD3 exonuclease catalytic activity. FICD AMP-transferase accelerates PLD3 degradation and induces cellular stress response. Furthermore, depletion of the two human AMP-transferases FICD and SelO point towards a complex regulatory network governing PLD3 AMPylation. Together, our findings demonstrate a critical role of AMPylation in PLD3 processing and regulation of its catalytic activity and provide new insights into the proteins transport and localization to lysosomes. The observation that PLD3 regulation in PD-derived neurons is altered compared to healthy neurons further highlights its role in neurodegenerative diseases.

biochemistry↗

bioRxiv2024

A regulatory module driving the recurrent evolution of irreducible molecular complexes.

To sustain life, molecular complexes require the concerted action of multiple proteins, each relying on one another to perform intricate tasks. However, how such interdependent protein interactions evolve in the first place is poorly understood. To address this, we investigated the origins of a group of fast-evolving genetic parasites--toxin-antidote elements--which boil down this dilemma to a simple question: what came first, the toxin or the antidote? By integrating quantitative genetics, biochemistry, and evolutionary genomics, we discovered that toxins and antidotes can arise simultaneously through the duplication of a regulatory module comprising an F-box protein in linkage to its substrate. Our findings provide one solution to the recurrent emergence of mutual dependence in protein complexes and illustrate in detail how complexity can swiftly arise from simplicity.

genomics↗

bioRxiv2019

Alpha-Synuclein is a Target of Fic-mediated Adenylylation/AMPylation: Implications for Parkinson’s Disease

During disease, cells experience various stresses that manifest as an accumulation of misfolded proteins and eventually lead to cell death. To combat this stress, cells activate a pathway called UPR (Unfolded Protein Response) that functions to maintain ER (endoplasmic reticulum) homeostasis and determines cell fate. We recently reported a hitherto unknown mechanism of regulating ER stress via a novel post-translational modification (PTM) called Fic-mediated Adenylylation/AMPylation. Specifically, we showed that the human Fic (filamentation induced by cAMP) protein, HYPE/FicD, catalyzes the addition of an AMP (adenosine monophosphate) to the ER chaperone, BiP, to alter the cells UPR-mediated response to misfolded proteins. Here, we report that we have now identified a second target for HYPE - alpha-Synuclein (Syn), a presynaptic protein involved in Parkinsons disease (PD). Aggregated Syn has been shown to induce ER stress and elicit neurotoxicity in PD models. We show that HYPE adenylylates Syn and reduces phenotypes associated with Syn aggregation in vitro, suggesting a possible mechanism by which cells cope with Syn toxicity.\n\nHIGHLIGHTSO_LIAggregated forms of the presynaptic protein Syn cause neurotoxicity and induce ER stress in cellular and animal models of Parkinsons disease.\nC_LIO_LIWe have identified Syn as a novel target for the human Fic protein, HYPE, a key regulator of ER homeostasis.\nC_LIO_LIHYPE adenylylates Syn and reduces the aggregation of recombinant Syn\nC_LIO_LIFic-mediated adenylylation/AMPylation is a possible mechanism by which cells cope with Syn toxicity.\nC_LI\n\nGraphic Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

biochemistry↗