Biomedical subjects

Christian Preisinger

Publications and source records attributed to Christian Preisinger.

8 recordsLinked to original sources

PubMed2026

Loss of the Mechanistic Target of Rapamycin Complex 1 Causes a Lethal Alpha-1 Antitrypsin Deficiency-Associated Liver Disease.

BACKGROUND & AIMS: SERPINA1 mutations cause retention of the otherwise secreted alpha-1 antitrypsin and lead to the proteotoxic alpha-1 antitrypsin deficiency-related liver disease. As mechanistic target of rapamycin is a key coordinator of proteostasis, we studied its role in alpha-1 antitrypsin deficiency-related liver disease. METHODS: PiZ mice overexpressing the characteristic SERPINA1 mutation were mated with rodents harboring a hepatocyte specific-ablation of the interaction partners regulatory-associated protein of mechanistic target of rapamycin or rapamycin-insensitive companion of mammalian target of rapamycin, corresponding to mechanistic target of rapamycin complexes 1 or 2, or with mice lacking mechanistic target of rapamycin. Serum proteomics, liver bulk proteomics, spatial proteomics, and metabolomics were applied to characterize molecular and metabolic alterations. RESULTS: At 2 months of age, PiZ-mTORΔhep and PiZ-RaptorΔhep but not PiZ-RictorΔhep mice showed signs of increased liver injury and mortality despite diminished hepatic alpha-1 antitrypsin accumulation. PiZ-RaptorΔhep animals displayed increased levels of the proapoptotic protein C/EBP homologous protein, but C/EBP homologous protein ablation did not rescue the phenotype. Serum proteomics revealed no signs of advanced synthetic liver failure but immature hepatocellular products. Liver bulk proteomics and small metabolite measurement demonstrated a metabolic reprogramming of PiZ-RaptorΔhep mice. Spatial proteomics revealed alterations in liver zonation with increased ammonia levels as the likely cause of death in PiZ-RaptorΔhep animals. CONCLUSIONS: In summary, in alpha-1 antitrypsin deficiency-related proteotoxic liver injury, regulatory-associated protein of mechanistic target of rapamycin preserves a liver zonation, thereby protecting from lethal metabolic dysregulation.

Animals↗

PubMed2025

Multidimensional OMICs reveal ARID1A orchestrated control of DNA damage, splicing, and cell cycle in normal-like and malignant urothelial cells.

Epigenetic regulators, such as the SWI/SNF complex, with important roles in tissue development and homeostasis, are frequently mutated in cancer. ARID1A, a subunit of the SWI/SNF complex, is mutated in approximately 20% of all bladder tumors; however, the consequences of this remain poorly understood. Finding truncations to be the most common mutation, we generated loss- and gain-of-function models to conduct RNA-Seq, interactome analyses, Omni-ATAC-Seq, and functional studies to characterize ARID1A-affected pathways potentially suitable for the treatment of ARID1A-deficient bladder cancers. We observed decreased cell proliferation and deregulation of stress-regulated pathways, including DNA repair, in ARID1A-deficient cells. Furthermore, ARID1A was linked to alternative splicing and translational regulation on RNA and interactome levels. ARID1A deficiency drastically reduced the accessibility of chromatin, especially around introns and distal enhancers, in a functional enrichment analysis. Less accessible chromatin areas were mapped to pathways such as cell proliferation and DNA damage response. Indeed, the G2/M checkpoint appeared impaired after DNA damage in ARID1A-deficient cells. Together, our data highlight the broad impact of ARID1A loss and the possibility of targeting proliferative and DNA repair pathways for treatment.

Transcription Factors↗

PubMed2005

Plk1 docking to GRASP65 phosphorylated by Cdk1 suggests a mechanism for Golgi checkpoint signalling.

GRASP65, a structural protein of the Golgi apparatus, has been linked to the sensing of Golgi structure and the integration of this information with the control of mitotic entry in the form of a Golgi checkpoint. We show that Cdk1-cyclin B is the major kinase phosphorylating GRASP65 in mitosis, and that phosphorylated GRASP65 interacts with the polo box domain of the polo-like kinase Plk1. GRASP65 is phosphorylated in its C-terminal domain at four consensus sites by Cdk1-cyclin B, and mutation of these residues to alanine essentially abolishes both mitotic phosphorylation and Plk1 binding. Expression of the wild-type GRASP65 C-terminus but not the phosphorylation defective mutant in normal rat kidney cells causes a delay but not the block in mitotic entry expected if this were a true cell cycle checkpoint. These findings identify a Plk1-dependent signalling mechanism potentially linking Golgi structure and cell cycle control, but suggest that this may not be a cell cycle checkpoint in the classical sense.

Amino Acid Sequence↗

PubMed2005

Kinases regulating Golgi apparatus structure and function.

Protein kinases control Golgi function in both mitotic and interphase cells. In mitosis, phosphorylation of structural proteins by Cdk1 (cyclin-dependent kinase 1)-cyclin B, Polo-like and mitogen-activated protein kinases underlie changes in Golgi reorganization during cell division. While in interphase, signalling pathways that are associated with the Golgi control secretory function through a variety of mechanisms. Some of these, notably those involving protein kinase D and Ste20 family kinases, are also relevant for the establishment and maintenance of cell polarization and migration.

Animals↗

PubMed2004

YSK1 is activated by the Golgi matrix protein GM130 and plays a role in cell migration through its substrate 14-3-3zeta.

The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.

14-3-3 Proteins↗

PubMed2003

The UIM domain of Hrs couples receptor sorting to vesicle formation.

Hepatocyte growth factor regulated tyrosine kinase substrate (Hrs), a main component of the 'bilayered' clathrin coat on sorting endosomes, was originally identified as a substrate of activated tyrosine kinase receptors. We have analysed Hrs phosphorylation in response to epidermal growth factor (EGF) stimulation and show that the evolutionary conserved tyrosines Y329 and Y334 provide the principal phosphorylation sites. Hrs is proposed to concentrate ubiquitinated receptors within clathrin-coated regions via direct interaction with its UIM (ubiquitin interaction motif) domain. We show that the same UIM domain is necessary for EGF-stimulated tyrosine phosphorylation of Hrs. Over-expression of wild-type Hrs or a double mutant, Y329/334F, defective in EGF-dependent phosphorylation, both substantially retard EGF receptor (EGFR) degradation by inhibiting internal vesicle formation and thereby preventing EGFR incorporation into lumenal vesicles of the multivesicular bodies. In contrast, mutation or deletion of the Hrs-UIM domain strongly suppresses this effect. In addition the UIM-deletion and point mutants are also observed on internal membranes, indicating a failure to dissociate from the endosomal membrane prior to incorporation of the receptor complex into lumenal vesicles. Our data suggest a role for the UIM-domain of Hrs in actively retaining EGFR at the limiting membrane of endosomes as a prelude to lumenal vesicle formation.

Biological Transport↗

PubMed2003

Phosphorylation of mitotic kinesin-like protein 2 by polo-like kinase 1 is required for cytokinesis.

We have investigated the function of mitotic kinesin-like protein (MKlp) 2, a kinesin localized to the central spindle, and demonstrate that its depletion results in a failure of cleavage furrow ingression and cytokinesis, and disrupts localization of polo-like kinase 1 (Plk1). MKlp2 is a target for Plk1, and phosphorylated MKlp2 binds to the polo box domain of Plk1. Plk1 also binds directly to microtubules and targets to the central spindle via its polo box domain, and this interaction controls the activity of Plk1 toward MKlp2. An antibody to the neck region of MKlp2 that prevents phosphorylation of MKlp2 by Plk1 causes a cytokinesis defect when introduced into cells. We propose that phosphorylation of MKlp2 by Plk1 is necessary for the spatial restriction of Plk1 to the central spindle during anaphase and telophase, and the complex of these two proteins is required for cytokinesis.

Cell Cycle Proteins↗

PubMed2002

The Rab6 GTPase regulates recruitment of the dynactin complex to Golgi membranes.

Dynactin is a multisubunit protein complex required for the activity of dynein in diverse intracellular motility processes, including membrane transport. Dynactin can bind to vesicles and liposomes containing acidic phospholipids, but general properties such as this are unlikely to explain the regulated recruitment of dynactin to specific sites on organelle membranes. Additional factors must therefore exist to control this process. Candidates for these factors are the Rab GTPases, which function in the tethering of vesicles to their target organelle prior to membrane fusion. In particular, Rab27a tethers melanosomes to the actin cytoskeleton. Other Rabs have been implicated in microtubule-dependent organelle motility; Rab7 controls lysosomal transport, and Rab6 is involved in microtubule-dependent transport pathways through the Golgi and from endosomes to the Golgi. We demonstrate that dynactin binds to Rab6 and shows a Rab6-dependent recruitment to Golgi membranes. Other Golgi Rabs do not bind to dynactin and are unable to support its recruitment to membranes. Rab6 therefore functions as a specificity or tethering factor controlling the recruitment of dynactin to membranes.

Animals↗