Biology subjects

Kahveci, S.

Publications and source records attributed to Kahveci, S..

3 recordsLinked to original sources

bioRxiv2024

Boosting Proteasome Activity: A Novel Mechanism of NMDAR Blockers Against Neurodegeneration

NMDAR antagonists, such as memantine and ketamine, have shown efficacy in treating neurodegenerative diseases and major depression. The mechanism by which these drugs correct the aforementioned diseases is still unknown. Our study reveals that these antagonists significantly enhance 20S proteasome activity, crucial for degrading intrinsically disordered, oxidatively damaged, or misfolded proteins, factors pivotal in neurodegenerative diseases like Alzheimers and Parkinsons. In a mouse model, ketamine administration notably altered brain synaptic protein profiles within two hours, downregulating proteins linked to neurodegenerative conditions. Furthermore, the altered proteins exhibited enrichment in terms related to plasticity and potentiation, including retrograde endocannabinoid signaling--a pivotal pathway in both short- and long-term plasticity that may elucidate the long-lasting effects of ketamine in major depression. Via the ubiquitin-independent 20S proteasome pathway (UIPS), these drugs maintain cellular protein homeostasis, crucial as proteasome activity declines with age leading to protein aggregation and disease symptoms. The elucidation of the mechanistic pathways underlying the therapeutic effects of NMDAR antagonists holds promise for developing new treatment strategies for brain diseases, including schizophrenia, Alzheimers, and Parkinsons.

neuroscience↗

bioRxiv2023

Pathological mutations reveal the key role of the iRhom2 N-terminus for ADAM17 binding, stability and activity.

The protease ADAM17 plays an important role in inflammation and cancer and is regulated by iRhom2. Mutations in the cytosolic N-terminus of human iRhom2 cause tylosis with oesophageal cancer (TOC). In mice, partial deletion of the N-terminus results in a curly hair phenotype (cub). These pathological consequences are consistent with our findings that iRhom2 is highly expressed in keratinocytes and in oesophageal cancer. Cub and TOC are associated with hyperactivation of ADAM17-dependent EGFR signalling. However, the underlying molecular mechanisms are not understood. We have identified a non-canonical, phosphorylation-independent 14-3-3 interaction site that encompasses all known TOC mutations. Disruption of this site dysregulates ADAM17 activity. The larger cub deletion also includes the TOC site and thus also dysregulated ADAM17 activity. The cub deletion, but not the TOC mutation, also causes severe reductions in stimulated shedding, binding, and stability of ADAM17, demonstrating the presence of additional regulatory sites in the N-terminus of iRhom2. Overall, this study contrasts the TOC and cub mutations, illustrates their different molecular consequences, and reveals important key functions of the iRhom2 N-terminus in regulating ADAM17.

molecular biology↗

bioRxiv2019

Glyoxal Does Not Preserve Cellular Proteins as Accurately as PFA: A Microscopical Survey of Epitopes

Chemical fixation is one of the most critical steps to retaining cellular targets as naturally as possible. Recent developments in microscopy allow sophisticated detection and measuring techniques with which spatio-temporal molecular alterations is conceivable. Here, we document the fixation competence of glyoxal (Gly), a less-toxic dialdehyde molecule, and paraformaldehyde (PFA) side-by-side (with or without Triton-X 100 permealization) in live- and fixed-cell preparations including human stem cells, spermatozoa, mouse oocytes/embryos using super-resolution microscopy. Although Gly seemed to act faster than PFA, catastrophic consequences were found not acceptable, especially in oocytes and embryos. Due to cell lysate and immunocytochemistry surveys, it was obvious that PFA is superior to Gly in retaining cellular proteins in situ with little/no background staining. In many samples, PFA revealed more reliable and consistent results regarding the protein quantity and cellular localization corresponding to previously defined patterns in the literature. Although the use of Gly is beneficial as indicated by previous reports, we concluded that it does not meet the requirement for proper fixation, at least for the tested cell types and proteins.

cell biology↗