Biology subjects

Mendiburo, M. J.

Publications and source records attributed to Mendiburo, M. J..

3 recordsLinked to original sources

bioRxiv2025

Canonical autophagy remains inactive in induced pluripotent stem cells and neuronal progenitor cells following DNA damage induced by BPDE or etoposide.

(Macro-)Autophagy is a key cellular stress response mediating the recycling of long-lived or damaged proteins and organelles. In stem cells, autophagy is essential for the decision between quiescence, self-renewal and differentiation. We observed that induced pluripotent stem cells (iPSCs) and thereof derived neural progenitor cells (NPCs) have a functional autophagy machinery, as shown by starvation-induced autophagic flux and ULK1 activation. Using the human iPSC line iPS11 and thereof derived NPCs (niPS11), we investigated whether genotoxic stress induced by benzo[a]pyrene diolepoxide (BPDE) or etoposide can similarly activate autophagy, as previously reported for cancer cell lines. While both BPDE and etoposide induced the DNA damage markers phospho-p53 Ser15 and {gamma}H2AX and slightly altered the expression of DNA repair proteins such as XPC, they did not trigger autophagic flux in either iPSCs or NPCs. After genotoxin treatment, ULK1 activation was only observed in NPCs, but this was not sufficient to trigger a significant downstream autophagic response. Mass spectrometry revealed minimal proteomic changes in iPSCs and moderate changes in NPCs, mainly involving mitotic regulators. These results suggest that genotoxic agents do not strongly affect canonical autophagy in pluripotent stem cells or their neural derivatives despite an otherwise responsive autophagic system.

cell biology↗

bioRxiv2025

Mitotic phosphorylation of Lamin B1 rod domain by ULK1 and Aurora A/PLK1 promotes spindle function.

The coil-coil rod domain that mediates lateral assembly of lamin filaments has been shown by proteomic approaches to undergo phosphorylation, though the function of these modifications remains unknown. Here, we identify serine 210 (S210) within the Lamin B1 rod domain as a mitotic phospho-acceptor residue, regulated by the combined action of the autophagy-activating kinase ULK1 and the mitotic kinases Aurora A and PLK1. Using a phospho-specific antibody, we demonstrate that Lamin B1 phospho-S210 is enriched at the mitotic spindle and interacts with a network of proteins involved in spindle assembly and spindle pole focusing. Preventing S210 phosphorylation increases the number of cells with multipolar or shorter spindles and prolongs mitotic duration. Our findings indicate that mitotic phosphorylation of Lamin B1 at S210 within the rod domain is important for proper spindle organization and focusing during mitosis.

cell biology↗

bioRxiv2024

Small-molecule inhibitor of C-terminal HSP90 dimerization modulates autophagy and functions synergistically with mTOR inhibition to kill cisplatin-resistant cancer cells

BackgroundA major obstacle for the successful treatment of cancer is the primary presence or development of resistance mechanisms toward therapeutic intervention. In urothelial cancer, cisplatin-based regimens are still routinely employed, and multiple cellular pathways contribute to chemoresistance. Since the identification of heat shock protein 90 (HSP90) as potential cancer target, various HSP90 inhibitors (HSP90i) have been developed and evaluated in clinical trials. However, limited efficacy has been observed, mainly caused by dose-limiting toxicity and the concomitant induction of a cytoprotective heat shock response (HSR). To avoid this effect, inhibitors targeting the C-terminal domain (CTD) of HSP90 that do not elicit an HSR have been put forward. Additionally, the crosstalk between autophagy and HSP90 is currently being explored, since both processes work together in proteostasis, and the modulation of autophagic responses might be helpful in order to improve the efficacy of HSP90 inhibitors. MethodsThe second-generation small-molecule inhibitor VWK147 targeting HSP90 CTD dimerization was synthesized and characterized in detail by biochemical cell-free and cellular assays and molecular modeling. Specifically, HSP90 inhibition, cell viability, and autophagy were monitored in mono- and combined treatments. ResultsWe demonstrate that VWK147 induces cell death in both cisplatin-sensitive and cisplatin-resistant urothelial carcinoma cells. The treatment with VWK147 in these cells led to the destabilization of classical HSP90 client proteins without triggering an HSR. Additionally, we observe that VWK147 re-sensitizes resistant urothelial carcinoma cells to cisplatin and--in combination with mTOR inhibition--synergistically kills cisplatin-sensitive and -resistant cells, in contrast to what is observed upon treatment with the N-terminal domain-targeting HSP90 inhibitor 17-AAG. This synergy may be explained by VWK147-mediated inhibition of late autophagy events, and thus a blockade of autophagic flux. Finally, we also observed that VWK147 induces non-canonical LC3 lipidation, indicating that this compound possibly exerts a broader effect on ion balance or pH of the endolysosomal system. ConclusionVWK147 is a promising inhibitor that targets the C-terminal dimerization of HSP90 and simultaneously exhibits autophagy-modulating effects. This compound could potentially be an effective option for improving anti-cancer therapies and/or overcoming treatment resistance.

cell biology↗