Molecular Biology and Genetics / Moleküler Biyoloji ve Genetik
Permanent URI for this collectionhttps://hdl.handle.net/11147/9
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Conference Object Investigation of the role of Wnt/β-catenin signaling in development of Alzheimer's disease in a zebrafish model of mmyloid-β toxicity(Wiley, 2024) Nazlı, Dilek; Ipekgil, D.; Poyraz, Y. K.; Catak, B.; Sahin, E. Turhanlar; Özhan, GüneşThe Wnt/β-catenin signaling pathway, an evolutionarily conserved and pivotal pathway associated with synapse formation in adulthood, plays a crucial role in Alzheimer's disease (AD). AD, marked by various pathologies, is primarily linked to the accumulation of extracellular beta-amyloid plaques. The interplay between this accumulation and disruptions in the Wnt/β-catenin signaling pathway triggers synaptic degeneration, resulting in synaptic dysfunction and AD progression. In this study, we modeled AD induced by the Aβ42 peptide using adult transgenic (6XTCF) zebrafish. To establish the zebrafish AD model, we employed cerebroventricular microinjection (CVMI) with the Aβ42 peptide. Fish, anesthetized prior to CVMI, were positioned on a stable platform, and the Aβ42 peptide was injected into the telencephalon region of the brain by a capillary needle. Brain samples were collected on 1, 3, 4, 7, and 14 days post-CVMI (dpi) to analyze changes in Aβ42 peptide accumulation, the immune system response, synaptic degeneration, apoptosis, and the expression of genes related to proliferation using qPCR and immunofluorescent staining. To examine the role of the Wnt/β-catenin signaling pathway in the molecular mechanism of AD development, fish exhibiting high levels of regeneration on days 7 and 14 were treated with the IWR-1 drug, which inhibits the Wnt/β-catenin signaling by stabilizing the Axin2 protein, thereby suppressing the regenerative response. Our results revealed that the AD model manifested on 3dpi, with the regenerative response reaching its peak on 7dpi and 14dpi. Treatment with IWR-1 resulted in increased Aβ42 accumulation, accelerated synaptic degeneration, and elevated cell deaths in fish where the Wnt signaling pathway was inhibited. In conclusion, our adult zebrafish AD model is poised to elucidate the molecular mechanisms connecting the Wnt signaling pathway and AD, thereby contributing to the development of alternative therapeutic approaches for AD patients.Article Citation - WoS: 6Citation - Scopus: 5Epitranscriptomics M6a Analyses Reveal Distinct M6a Marks Under Tumor Necrosis Factor Α (tnf-Α) Apoptotic Conditions in Hela Cells(Wiley, 2024) Akçaöz Alasar, Azime; Tuncel, Özge; Sağlam, Buket; Gazaloğlu, Yasemin; Atbinek, Melis; Çağıral, Umut; İşcan, Evin; Özhan, Güneş; Akgül, BünyaminTumor necrosis factor-alpha (TNF-alpha) is a ligand that induces both intrinsic and extrinsic apoptotic pathways in HeLa cells by modulating complex gene regulatory mechanisms. However, the full spectrum of TNF-alpha-modulated epitranscriptomic m(6)A marks is unknown. We employed a genomewide approach to examine the extent of m(6)A RNA modifications under TNF-alpha-modulated apoptotic conditions in HeLa cells. miCLIP-seq analyses revealed a plethora of m(6)A marks on 632 target mRNAs with an enrichment on 99 mRNAs associated with apoptosis. Interestingly, the m(6)A RNA modification patterns were quite different under cisplatin- and TNF-alpha-mediated apoptotic conditions. We then examined the abundance and translational efficiencies of several mRNAs under METTL3 knockdown and/or TNF-alpha treatment conditions. Our analyses showed changes in the translational efficiency of TP53INP1 mRNA based on the polysome profile analyses. Additionally, TP53INP1 protein amount was modulated by METTL3 knockdown upon TNF-alpha treatment but not CP treatment, suggesting the existence of a pathway-specific METTL3-TP53INP1 axis. Congruently, METLL3 knockdown sensitized HeLa cells to TNF-alpha-mediated apoptosis, which was also validated in a zebrafish larval xenograft model. These results suggest that apoptotic pathway-specific m(6)A methylation marks exist in cells and TNF-alpha-METTL3-TP53INP1 axis modulates TNF-alpha-mediated apoptosis in HeLa cells.Article Citation - WoS: 14Citation - Scopus: 14Comparative Membrane Lipidomics of Hepatocellular Carcinoma Cells Reveals Diacylglycerol and Ceramide as Key Regulators of Wnt/Β-catenin Signaling and Tumor Growth(Wiley, 2023) Heger, Guillaume; Azbazdar, Yağmur; Demirci, Yeliz; İpekgil, Doğaç; Karabiçici, Mustafa; Özhan, GüneşHepatocellular carcinoma (HCC) is largely associated with aberrant activation of Wnt/beta-catenin signaling. Nevertheless, how membrane lipid composition is altered in HCC cells with abnormal Wnt signaling remains elusive. Here, by exploiting comprehensive lipidome profiling, we unravel the membrane lipid composition of six different HCC cell lines with mutations in components of Wnt/beta-catenin signaling, leading to differences in their endogenous signaling activity. Among the differentially regulated lipids are diacylglycerol (DAG) and ceramide, which were downregulated at the membrane of HCC cells after Wnt3a treatment. DAG and ceramide enhanced Wnt/b-catenin signaling by inducing caveolin-mediated endocytosis of the canonical Wnt-receptor complex, while their depletion suppressed the signaling activity along with a reduction of caveolin-mediated endocytosis in SNU475 and HepG2 cells. Moreover, depletion of DAG and ceramide significantly impeded the proliferation, tumor growth, and in vivo migration capacity of SNU475 and HepG2 cells. This study, by pioneering plasma membrane lipidome profiling in HCC cells, exhibits the remarkable potential of lipids to correct dysregulated signaling pathways in cancer and stop abnormal tumor growth.