Wiederkehr, A. | Search bioRxiv

bioRxiv2025

Perilysosomal Ca2+ overload impairs autophagic degradation in β-cell lipotoxicity

Saturated fatty acids impose lipotoxic stress on pancreatic {beta}-cells, leading to {beta}-cell failure and diabetes. In this study, we investigate the critical role of organellar Ca2+ disturbance on defective autophagy and {beta}-cell lipotoxicity. Palmitate, a saturated fatty acid, induced perilysosomal Ca2+ elevation, sustained mTORC1 activation on the lysosomal membrane, suppression of the lysosomal transient receptor potential mucolipin 1 (TRPML1) channel, and accumulation of undigested autophagosomes in {beta}-cells. These Ca2+ aberrations with autophagy defects by palmitate were prevented by a mTORC1 inhibitor or a mitochondrial superoxide scavenger. To alleviate perilysosomal Ca2+ overload, strategies such as lowering extracellular Ca2+, employing voltage-gated Ca2+ channel blocker or ATP-sensitive K+ channel opener effectively abrogated mTORC1 activation and preserved autophagy. Furthermore, redirecting perilysosomal Ca2+ into the endoplasmic reticulum (ER) with an ER Ca2+ ATPase activator, restores TRPML1 activity, promotes autophagic flux, and improves survival of {beta}-cells exposed to palmitate-induced lipotoxicity. Our findings suggest oxidative stress-Ca2+ overload-mTORC1 pathway involves in TRPML1 suppression and defective autophagy during {beta}-cell lipotoxicity. Restoring perilysosomal Ca2+ homeostasis emerges as a promising therapeutic strategy for metabolic diseases.

physiology↗

bioRxiv2023

Epitope Engineered Human Haematopoietic Stem Cells are Shielded from CD123-targeted Immunotherapy

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE) or chimeric antigen receptor (CAR) cells is very effective for haematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for immunotherapy of myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various haematological malignancies, including acute myeloid leukaemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). However, shared expression of CD123 on healthy haematopoietic stem and progenitor cells (HSPCs) bears the risk for extensive myelotoxicity upon targeted depletion. Here, we demonstrate that rationally designed, epitope-engineered HSPCs were completely shielded from CD123-targeted immunotherapy but remained fully functional while CD123-deficient HSPCs displayed a competitive disadvantage. Thus, molecularly shielded HSPCs could allow tumor-selective targeted immunotherapy and in parallel enable rebuilding a fully functional haematopoietic system. We envision that this approach is broadly applicable to many targets and cells, could render hitherto undruggable targets accessible to immunotherapy and will allow continued posttransplant immunotherapy, for instance to treat minimal residual disease (MRD) or be used as a salvage therapy. Since the function of the engineered targets is preserved, multiplexed molecular shielding could also enable targeted combination immunotherapies to address tumor heterogeneity. More generally, epitope shielding will be applicable for replacement of other cell types including the many immune cells which are currently being considered for engineered cellular therapies.

bioengineering↗