Biology subjects

Stephan, D.

Publications and source records attributed to Stephan, D..

5 recordsLinked to original sources

bioRxiv2025

Mutations in specific MT5-MMP domains prevent the accumulation of toxic APP metabolites and serve as templates for peptide-based therapeutics in cell models of Alzheimer's disease

Our prior work established a pivotal role for membrane-type 5-matrix metalloproteinase (MT5-MMP) in Alzheimers disease (AD) pathogenesis, particularly through its C-terminal transmembrane (TM) and intracellular (IC) domains, which influence the fate of major toxic metabolites of toxic amyloid precursor protein (APP) metabolites, particularly C99 and A{beta}. Hypothesizing that modifications in these domains could modulate C99 and A{beta} levels, we engineered MT5-MMP variants with deletions or substitutions in the TM/IC domains or specific IC amino acid clusters. When co-transfected into human cell lines accumulating C99, certain IC domain mutations promoted C99 degradation and reduced A{beta} levels, while other mutations had divergent effects. High content imaging further revealed that MT5-MMP IC domain modification altered C99 subcellular trafficking within the endomembrane system, impacting its processing. Proximity ligation assays confirmed the importance of the IC domain in MT5-MMP colocalization and potential interaction with C99. To translate these findings, we synthetized peptides mimicking the MT5-MMP IC domain, incorporating mutations that reduce C99 and/or A{beta} levels. One peptide effectively lowered C99 levels in an in vitro AD model. Overall, this study highlights the importance of specific amino acids in the C-terminal domains of MT5-MMP for regulating C99 and A{beta} metabolism. It also provides new insights for developing MT5-MMP-based therapeutic strategies against AD, exploiting the unique properties of specific mutations in MT5-MMP to prevent toxic accumulation of C99 and A{beta}. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=86 SRC="FIGDIR/small/655451v3_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@a6b04aorg.highwire.dtl.DTLVardef@1800721org.highwire.dtl.DTLVardef@542505org.highwire.dtl.DTLVardef@4a6d7b_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGRAPHICAL ABSTRACTC_FLOATNO C_FIG

cell biology↗

bioRxiv2024

The effectiveness of two new Metarhizium brunneum formulations against wireworms in potato cultivation

In the absence of officially approved agrochemicals for the use against wireworms (Agriotes spp.) in German potato cultivation, the entomopathogenic fungus genus Metarhizium has been regarded as promising biocontrol agent. However, previous mycoinsecticide formulations of M. brunneum could not achieve consistent effectiveness in field use. Within the scope of the project AgriMet, the effectiveness of two new formulations of M. brunneum was evaluated over three years in the field, greenhouse and laboratory. The application of a soil granule and/or a wettable powder (dry product) of M. brunneum during potato planting aimed to reduce potato tuber damage by controlling wireworms. During field trials in the Lower Saxony (Germany), the combination of both formulations led to an effectiveness between 1 % and 13.6 % compared to the untreated control. The single application of the AgriMet-Granule and the AgriMet-Dry Product was less successful. The standardised greenhouse set-up in pots with A. obscurus indicated that an application rate of at least 300 kg ha-1 of the AgriMet-Granule, respectively 1x1013 conidia ha-1 of the AgriMet-Dry Product was necessary to effectively reduce tuber damage (44-54 %), while surprisingly no larval mortality was recorded. The laboratory experiments showed, that only the AgriMet-Dry Product provided a lethal potential against wireworms, whereas the AgriMet-Granule showed deficits in terms of product quality. However, the effectiveness of the AgriMet-Dry Product against A. obscurus, A. sputator and A. lineatus resulted in significant differences in mortality indicating a species-specific virulence of the M. brunneum isolate used. Additional influencing factors became apparent through analysing multiple soil parameters at the respective field site such as temperature, moisture, colony-forming units of Metarhizium spp. and wireworm density, underlining the complexity of wireworm control using a microbial control agent. Especially the low soil temperatures during spring application pose a serious challenge to the development of an effective control strategy against wireworms.

microbiology↗

bioRxiv2024

Interaction of the wireworm species Agriotes obscurus, A. sputator and A. lineatus with a new granule formulation of Metarhizium brunneum

The attract-and-kill strategy is a promising approach in integrated pest management to increase the efficiency of plant protection products by pushing the required contact between target pest and active ingredient. Within the project AgriMet, a new soil granule of the entomopathogenic fungus Metarhizium brunneum was developed to control wireworms of the genus Agriotes (Coleoptera: Elateridae) in potato cultivation. The formulation is based on autoclaved millet as a substrate to lure the larvae to the infectious conidia on its surface. However, no data existed about the interactions of wireworms with the AgriMet-Granule. Here, I examined the behavioural response of the wireworm species A. obscurus, A. sputator and A. lineatus to the AgriMet-Granule using an olfactometric bioassay in the laboratory. The foraging behaviour of A. obscurus and A. sputator, with regard to the AgriMet-Granule, was tested with a feed-choice-experiment using a horizontal arena set-up. The tested wireworms significantly preferred autoclaved millet compared to the control. Fungal colonisation on the surface of the AgriMet-Granule did not influence their preference in general. However, differences were observed depending on the respective wireworm species and the two Metarhizium spp. isolates used. The feeding bioassay showed that the acceptance of wireworms for the AgriMet-Granule, with a low conidia concentration on its surface, was high. A high conidia concentration on the surface of the AgriMet-Granule led to a decreased acceptance that differed between the wireworm species. However, the survival analysis of wireworms isolated after the feed choice experiment indicated that the wireworms came in contact with the infectious conidia. Overall, the data suggests that autoclaved millet is a suitable substrate for the AgriMet-Granule. It attracts larvae of the genus Agriotes to the biocontrol agent using the formulated M. brunneum isolate.

microbiology↗

bioRxiv2021

The Alzheimer's disease risk factor APOE4 drives pro-inflammation in human astrocytes via HDAC-dependent repression of TAGLN3

The Apolipoprotein E4 (APOE4) is the major allelic risk factor for late-onset Alzheimers disease (AD). APOE4 associates with a pro-inflammatory phenotype increasingly considered as critical in AD initiation and progression. Yet, the mechanisms driving an APOE4-dependent neuroinflammation remain unelucidated. Leveraging patient specific human induced Pluripotent Stem Cells (iPSCs) we demonstrate inflammatory chronicity and hyperactivated responses upon cytokines in human APOE4 astrocytes via a novel mechanism. We uncovered that APOE4 represses Transgelin 3 (TAGLN3), a new interacting partner of I{kappa}B, thus increasing the NF-kB activity. The transcriptional repression of TAGLN3 was shown to result from an APOE4-dependent histone deacetylase (HDAC) activity. The functional relevance of TAGLN3 was demonstrated by the attenuation of APOE4-driven neuroinflammation after TAGLN3 supplementation. Importantly, TAGLN3 downregulation was confirmed in the brain of AD patients. Our findings highlight the APOE4-TAGLN3 axis as a new pathogenic pathway that paves the way for the development of therapeutics to prevent maladaptive inflammatory responses in APOE4 carriers, while placing TAGLN3 downregulation as a potential biomarker of AD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=98 HEIGHT=200 SRC="FIGDIR/small/440108v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1036557org.highwire.dtl.DTLVardef@1f245bdorg.highwire.dtl.DTLVardef@c07c4aorg.highwire.dtl.DTLVardef@1200396_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

MT5-MMP controls APP metabolism and the fate of beta-CTF/C99 and Abeta through proteolytic-dependent and -independent mechanisms relevant for Alzheimer's disease

We previously discovered the implication of membrane-type 5-matrix metalloproteinase (MT5-MMP) in Alzheimers disease AD pathogenesis. Here we shed new light on pathogenic mechanisms by which MT5-MMP controls APP processing and the fate of amyloid beta peptide (A{beta}), its precursor C99 and C83. We found in HEK carrying the APP Swedish familial mutation (HEKswe) that MT5-MMP-mediated processing of APP that releases the soluble 95 kDa form (sAPP95), was hampered by the removal of the C-terminal non-catalytic domains of MT5-MMP. Catalytically inactive MT5-MMP variants increased the levels of A{beta} and promoted APP/C99 sorting in the endo-lysosomal system. We found interaction of C99 with the C-terminal portion of MT5-MMP, the deletion of which caused a strong degradation of C99 by the proteasome, preventing A{beta} accumulation. These findings reveal novel mechanisms for MT5-MMP control of APP metabolism and C99 fate involving proteolytic and non-proteolytic actions mainly mediated by the C-terminal part of the proteinase.

neuroscience↗