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Kremser, L.

Publications and source records attributed to Kremser, L..

2 recordsLinked to original sources

Acute lysosome repositioning reveals functional and proteomic adaptations

Lysosomes exhibit spatial heterogeneity, but establishing causal relationships remains challenging with existing relocalization strategies. We present a modular toolkit that rapidly repositions lysosomes on demand by recruiting inducible motors. This decouples the location of organelles from systemic stress. We demonstrate that peripheral lysosomes adapt quickly by exhibiting luminal alkalinization and reduced proteolytic capacity. Furthermore, peripheral sequestration impairs autophagic flux by creating a spatial "trafficking bottleneck". We use this system to provide an unbiased proteomic characterization of spatially distinct lysosomal populations using mass spectrometry. Our findings reveal a distinct set of proteins and complexes that are spatially partitioned between perinuclear and peripheral lysosomes. Perinuclear lysosomes are configured for metabolic recycling. They have a high density of V1 V-ATPase subunits and contain the nucleoside transporter SLC29A3. Conversely, peripheral lysosomes serve as secretory outposts that are enriched in cathepsin Z and the SPG11/SPG15/AP5 complex. These validated cell lines and extensive datasets provide a flexible framework for investigating the functional specialization of different lysosome populations.

cell biology↗

The Dsc ubiquitin ligase complex identifies transmembrane degrons to degrade orphaned proteins at the Golgi

The Golgi apparatus is essential for protein sorting, yet its quality control mechanisms are poorly understood. Here we show that the Dsc ubiquitin ligase complex, particularly the rhomboid pseudo-protease subunit, Dsc2, assesses the hydrophobic length of -helical transmembrane domains (TMDs) at the Golgi. Thereby the Dsc complex interacts with orphaned ER and Golgi proteins that have shorter TMDs and ubiquitinates them for targeted degradation. Some Dsc substrates will be K63 polyubiquitinated for ESCRT dependent vacuolar degradation or K48 polyubiquitinated for endosome and Golgi associated proteasomal degradation (EGAD). Other Dsc substrates are exclusively extracted by Cdc48 for EGAD. The accumulation of Dsc substrates entails a specific increase in glycerophospholipids with shorter and asymmetric fatty acyl chains. Hence, the Dsc complex mediates the selective degradation of orphaned proteins at the sorting center of cells, which prevents their spreading across other organelles and thus preserves cellular membrane protein and lipid composition.

cell biology↗