| 1. |
- Cortese, Katia, et al.
(författare)
-
The HSP90 inhibitor geldanamycin perturbs endosomal structure and drives recycling ErbB2 and transferrin to modified MVBs/lysosomal compartments
- 2013
-
Ingår i: Molecular Biology of the Cell. - : The American Society for Cell Biology. - 1059-1524 .- 1939-4586. ; 24:2, s. 129-144
-
Tidskriftsartikel (refereegranskat)abstract
- The ErbB2 receptor is a clinically validated cancer target whose internalization and trafficking mechanisms remain poorly understood. HSP90 inhibitors, such as geldanamycin (GA), have been developed to target the receptor to degradation or to modulate downstream signaling. Despite intense investigations, the entry route and postendocytic sorting of ErbB2 upon GA stimulation have remained controversial. We report that ErbB2 levels inversely impact cell clathrin-mediated endocytosis (CME) capacity. Indeed, the high levels of the receptor are responsible for its own low internalization rate. GA treatment does not directly modulate ErbB2 CME rate but it affects ErbB2 recycling fate, routing the receptor to modified multivesicular endosomes (MVBs) and lysosomal compartments, by perturbing early/recycling endosome structure and sorting capacity. This activity occurs irrespective of the cargo interaction with HSP90, as both ErbB2 and the constitutively recycled, HSP90-independent, transferrin receptor are found within modified endosomes, and within aberrant, elongated recycling tubules, leading to modified MVBs/lysosomes. We propose that GA, as part of its anticancer activity, perturbs early/recycling endosome sorting, routing recycling cargoes toward mixed endosomal compartments.
|
|
| 2. |
- Doherty, Gary J., et al.
(författare)
-
The endocytic protein GRAF1 is directed to cell-matrix adhesion sites and regulates cell spreading
- 2011
-
Ingår i: Molecular Biology of the Cell. - Bethesda : American Society for Cell Biology. - 1059-1524 .- 1939-4586. ; 22:22, s. 4380-4389
-
Tidskriftsartikel (refereegranskat)abstract
- The rho GTPase-activating protein GTPase regulator associated with focal adhesion kinase-1 (GRAF1) remodels membranes into tubulovesicular clathrin-independent carriers (CLICs) mediating lipid-anchored receptor endocytosis. However, the cell biological functions of this highly prevalent endocytic pathway are unclear. In this article, we present biochemical and cell biological evidence that GRAF1 interacted with a network of endocytic and adhesion proteins and was found enriched at podosome-like adhesions and src-induced podosomes. We further demonstrate that these sites comprise microdomains of highly ordered lipid enriched in GRAF1 endocytic cargo. GRAF1 activity was upregulated in spreading cells and uptake via CLICs was concentrated at the leading edge of migrating cells. Depletion of GRAF1, which inhibits CLIC generation, resulted in profound defects in cell spreading and migration. We propose that GRAF1 remodels membrane microdomains at adhesion sites into endocytic carriers, facilitating membrane turnover during cell morphological changes.
|
|
| 3. |
- Lundmark, Richard, et al.
(författare)
-
The GTPase-activating protein GRAF1 regulates the CLIC/GEEC endocytic pathway
- 2008
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 18:22, s. 1802-1808
-
Tidskriftsartikel (refereegranskat)abstract
- Clathrin-independent endocytosis is an umbrella term for a variety of endocytic pathways that internalize numerous cargoes independently of the canonical coat protein Clathrin [1, 2]. Electron-microscopy studies have defined the pleiomorphic CLathrin-Independent Carriers (CLICs) and GPI-Enriched Endocytic Compartments (GEECs) as related major players in such uptake [3, 4]. This CLIC/GEEC pathway relies upon cellular signaling and activation through small G proteins, but mechanistic insight into the biogenesis of its tubular and tubulovesicular carriers is lacking. Here we show that the Rho-GAP-domain-containing protein GRAF1 marks, and is indispensable for, a major Clathrin-independent endocytic pathway. This pathway is characterized by its ability to internalize bacterial exotoxins, GPI-linked proteins, and extracellular fluid. We show that GRAF1 localizes to PtdIns(4,5)P2-enriched, tubular, and punctate lipid structures via N-terminal BAR and PH domains. These membrane carriers are relatively devoid of caveolin1 and flotillin1 but are associated with activity of the small G protein Cdc42. This study provides the first specific noncargo marker for CLIC/GEEC endocytic membranes and demonstrates how GRAF1 can coordinate small G protein signaling and membrane remodeling to facilitate internalization of CLIC/GEEC pathway cargoes.
|
|
| 4. |
- Morén, Björn, et al.
(författare)
-
EHD2 regulates caveolar dynamics via ATP-driven targeting and oligomerization
- 2012
-
Ingår i: Molecular Biology of the Cell. - : American society for cell biology. - 1059-1524 .- 1939-4586. ; 23:7, s. 1316-1329
-
Tidskriftsartikel (refereegranskat)abstract
- Eps15 homology domain-containing 2 (EHD2) belongs to the EHD-containing protein family of dynamin-related ATPases involved in membrane remodeling in the endosomal system. EHD2 dimers oligomerize into rings on highly curved membranes, resulting in stimulation of the intrinsic ATPase activity. In this paper, we report that EHD2 is specifically and stably associated with caveolae at the plasma membrane and not involved in clathrin-mediated endocytosis or endosomal recycling, as previously suggested. EHD2 interacts with pacsin2 and cavin1, and ordered membrane assembly of EHD2 is dependent on cavin1 and caveolar integrity. While the EHD of EHD2 is dispensable for targeting, we identified a loop in the nucleotide-binding domain that, together with ATP binding, is required for caveolar localization. EHD2 was not essential for the formation or shaping of caveolae, but high levels of EHD2 caused distortion and loss of endogenous caveolae. Assembly of EHD2 stabilized and constrained caveolae to the plasma membrane to control turnover, and depletion of EHD2, resulting in endocytic and more dynamic and short-lived caveolae. Thus, following the identification of caveolin and cavins, EHD2 constitutes a third structural component of caveolae involved in controlling the stability and turnover of this organelle.
|
|
| 5. |
- Howes, Mark T, et al.
(författare)
-
Clathrin-independent carriers form a high capacity endocytic sorting system at the leading edge of migrating cells
- 2010
-
Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 190:4, s. 675-691
-
Tidskriftsartikel (refereegranskat)abstract
- Although the importance of clathrin- and caveolin-independent endocytic pathways has recently emerged, key aspects of these routes remain unknown. Using quantitative ultrastructural approaches, we show that clathrin-independent carriers (CLICs) account for approximately three times the volume internalized by the clathrin-mediated endocytic pathway, forming the major pathway involved in uptake of fluid and bulk membrane in fibroblasts. Electron tomographic analysis of the 3D morphology of the earliest carriers shows that they are multidomain organelles that form a complex sorting station as they mature. Proteomic analysis provides direct links between CLICs, cellular adhesion turnover, and migration. Consistent with this, CLIC-mediated endocytosis of key cargo proteins, CD44 and Thy-1, is polarized at the leading edge of migrating fibroblasts, while transient ablation of CLICs impairs their ability to migrate. These studies provide the first quantitative ultrastructural analysis and molecular characterization of the major endocytic pathway in fibroblasts, a pathway that provides rapid membrane turnover at the leading edge of migrating cells.
|
|
| 6. |
- Jones, Felicity C., et al.
(författare)
-
The genomic basis of adaptive evolution in threespine sticklebacks
- 2012
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 484:7392, s. 55-61
-
Tidskriftsartikel (refereegranskat)abstract
- Marine stickleback fish have colonized and adapted to thousands of streams and lakes formed since the last ice age, providing an exceptional opportunity to characterize genomic mechanisms underlying repeated ecological adaptation in nature. Here we develop a high-quality reference genome assembly for threespine sticklebacks. By sequencing the genomes of twenty additional individuals from a global set of marine and freshwater populations, we identify a genome-wide set of loci that are consistently associated with marine-freshwater divergence. Our results indicate that reuse of globally shared standing genetic variation, including chromosomal inversions, has an important role in repeated evolution of distinct marine and freshwater sticklebacks, and in the maintenance of divergent ecotypes during early stages of reproductive isolation. Both coding and regulatory changes occur in the set of loci underlying marine-freshwater evolution, but regulatory changes appear to predominate in this well known example of repeated adaptive evolution in nature.
|
|
