Biology subjects

Lörincz, P.

Publications and source records attributed to Lörincz, P..

3 recordsLinked to original sources

bioRxiv2026

The Uvrag-containing PI3K complex promotes Hsc70-4 dependent endosomal clathrin removal and lysosomal maturation in Drosophila nephrocytes

The class III phosphatidylinositol 3-kinase complex (PI3K(III)) generates phosphatidylinositol-3-phosphate (PI(3)P), a lipid that defines endosomal membrane identity. Two PI3K(III) complexes share core subunits but differ in their fourth component: the Atg14-containing complex I functions in autophagy, whereas the Uvrag-containing complex II is required for endosomal maturation. Despite this, the mechanism by which complex II promotes lysosomal function remains unclear. Using Drosophila nephrocytes, we show that PI(3)P is enriched on Rab7-positive late endosomes and that the Hsp70 chaperone Hsc70-4 binds phosphoinositides. Loss of PI3K complex II disrupts endolysosomal organization and phenocopies Hsc70-4 inhibition. In both cases, clathrin accumulates on intracellular, often endosomal membranes, Rab7 compartments are disorganized, and abnormal endolysosomal structures form. These defects are accompanied by impaired HOPS recruitment, lysosomal dysfunction, and secretion of endolysosomal content. Importantly, clathrin depletion partially rescues these defects. Together, our findings identify a role for PI3K complex II in promoting clathrin removal from endosomal membranes and link PI(3)P and Hsc70-4 activity to lysosomal maturation.

cell biology↗

bioRxiv2024

The Rab7-Epg5 and Rab39-ema modules cooperately position autophagosomes for efficient lysosomal fusions

Macroautophagy, a major self-degradation pathway in eukaryotic cells, utilizes autophagosomes to transport self-material to lysosomes for degradation. While microtubular transport is crucial for the proper function of autophagy, the exact roles of factors responsible for positioning autophagosomes remain incompletely understood. In this study, we performed a loss-of-function genetic screen targeting genes potentially involved in microtubular motility. A genetic background that blocks autophagosome-lysosome fusions was used to accurately analyze autophagosome positioning. We discovered that pre-fusion autophagosomes move towards the non-centrosomal microtubule organizing center (ncMTOC) in Drosophila fat cells, which requires a dynein-dynactin complex. This process is regulated by the small GTPases Rab7 and Rab39 together with their adaptors: Epg5 and ema, respectively. The dynein-dependent movement of vesicles toward the nucleus/ncMTOC is essential for efficient autophagosomal fusions with lysosomes and subsequent degradation. Remarkably, altering the balance of kinesin and dynein motors changes the direction of autophagosome movement, indicating a competitive relationship where normally dynein-mediated transport prevails. Since pre-fusion lysosomes were positioned similarly to autophagosomes, it indicates that pre-fusion autophagosomes and lysosomes converge at the ncMTOC, which increases the efficiency of vesicle fusions.

cell biology↗

bioRxiv2023

Complex-specific subunits of endosomal tethering factors determine the balance between HOPS/CORVET complexes

The endolysosomal tethering complexes HOPS and CORVET play pivotal roles in the homo- and heterotypic fusion of early and late endosomes, respectively, and HOPS also mediates the fusion of lysosomes with incoming vesicles including late endosomes and autophagosomes. These heterohexameric complexes share their four core subunits that assemble with additional two, complex-specific subunits. These features and the similar structure of the complexes allow the formation of hybrid complexes, and the complex specific subunits may compete for binding to the core. In our study, we decided to gain insight into how human HOPS and CORVET complexes form. We found that the overexpression of CORVET-specific Vps8 or Tgfbrap1 decreased the amount of core proteins Vps11 and Vps18 that are assembled with HOPS-specific subunits Vps41 or Vps39, which suggests reduced amount of intracellular HOPS. In line with this, we observed that the level of lipidated LC3 protein was elevated in these cells and the autophagic cargo p62 showed accumulation in cells overexpressing Vps8, suggesting failure in autophagosome-lysosome fusion in line with loss of HOPS function. In contrast, overexpression of HOPS-specific Vps39 or Vps41 did not affect the levels of these autophagic markers. Finally, we found that a hybrid complex containing Vps39 and Vps8 could be formed in HEK293 cells.

cell biology↗