Endocytic membrane turnover at the leading edge is driven by a transient interaction between Cdc42 and GRAF1

Francis, Monika K.; Holst, Mikkel R.; Vidal-Quadras, Maite; Henriksson, Sara; Santarella-Mellwig, Rachel; Sandblad, Linda; Lundmark, Richard

doi:10.1242/jcs.174417

Cited by 33 publications

(50 citation statements)

References 39 publications

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“…The above model predicts that Graf acts at the plasma membrane to recruit EGFR to GEEC endocytosis. However, in line with previous work demonstrating that the assembly of mammalian GRAF1 at the cell surface is very transient (Francis et al, 2015), Graf was barely detected at the cell surface in hemocytes and S2R+ cells (Fig. S3A-E).…”

Section: Ubiquitin-dependent Interactions Of Egfr With Grafsupporting

confidence: 91%

Graf regulates hematopoiesis through GEEC endocytosis of EGFR

et al. 2017

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GTPase regulator associated with focal adhesion kinase 1 (GRAF1) is an essential component of the GPI-enriched endocytic compartment (GEEC) endocytosis pathway. Mutations in the human gene are associated with acute myeloid leukemia, but its normal role in myeloid cell development remains unclear. We show that Graf, the ortholog of GRAF1, is expressed and specifically localizes to GEEC endocytic membranes in macrophage-like plasmatocytes. We also find that loss of Graf impairs GEEC endocytosis, enhances EGFR signaling and induces a plasmatocyte overproliferation phenotype that requires the EGFR signaling cascade. Mechanistically, Graf-dependent GEEC endocytosis serves as a major route for EGFR internalization at high, but not low, doses of the predominant EGFR ligand Spitz (Spi), and is indispensable for efficient EGFR degradation and signal attenuation. Finally, Graf interacts directly with EGFR in a receptor ubiquitylation-dependent manner, suggesting a mechanism by which Graf promotes GEEC endocytosis of EGFR at high Spi. Based on our findings, we propose a model in which Graf functions to downregulate EGFR signaling by facilitating Spi-induced receptor internalization through GEEC endocytosis, thereby restraining plasmatocyte proliferation.

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Section: Ubiquitin-dependent Interactions Of Egfr With Grafsupporting

confidence: 91%

Graf regulates hematopoiesis through GEEC endocytosis of EGFR

et al. 2017

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“…Since the stalled vesicles were negative for Rab5 (Francis et al, 2015), we wanted to investigate whether other members of the Rab family were involved in this pathway. We transiently co-transfected GFP–GRAF1 Flp-In T-REx HeLa cells with Myc–Cdc42Q61L and DsRed–Rab7, mCherry–Rab8 or DsRed–Rab11 (Rab7a, Rab8a and Rab11a isoforms).…”

Section: Resultsmentioning

confidence: 99%

Endocytic turnover of Rab8 controls cell polarization

Vidal-Quadras

Holst

Francis

et al. 2017

Journal of Cell Science

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Adaptation of cell shape and polarization through the formation and retraction of cellular protrusions requires balancing of endocytosis and exocytosis combined with fine-tuning of the local activity of small GTPases like Rab8. Here, we show that endocytic turnover of the plasma membrane at protrusions is directly coupled to surface removal and inactivation of Rab8. Removal is induced by reduced membrane tension and mediated by the GTPase regulator associated with focal adhesion kinase-1 (GRAF1, also known as ARHGAP26), a regulator of clathrin-independent endocytosis. GRAF1-depleted cells were deficient in multi-directional spreading and displayed elevated levels of GTP-loaded Rab8, which was accumulated at the tips of static protrusions. Furthermore, GRAF1 depletion impaired lumen formation and spindle orientation in a 3D cell culture system, indicating that GRAF1 activity regulates polarity establishment. Our data suggest that GRAF1-mediated removal of Rab8 from the cell surface restricts its activity during protrusion formation, thereby facilitating dynamic adjustment of the polarity axis.

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“…The participation of RhoA and Cdc42 suggests that CIE of PDGFRβ may proceed via more than one mechanism. The activity of Cdc42 is known to be required for the CLIC and GEEC route (Lundmark et al, 2008;Francis et al, 2015). This pathway mediates uptake of CD44 as a typical cargo molecule and involves galectin-3 as an extracellular clustering adaptor that drives the formation of endocytic intermediates (Lakshminarayan et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Multiple routes of endocytic internalization of PDGFRβ contribute to PDGF-induced STAT3 signaling

Jastrzębski

Zdżalik-Bielecka

Mamińska

et al. 2017

Journal of Cell Science

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Platelet-derived growth factor receptor β (PDGFRβ) is a receptor tyrosine kinase which upon activation by PDGF-BB stimulates cell proliferation, migration and angiogenesis. Ligand binding induces intracellular signaling cascades but also internalization of the receptor, eventually resulting in its lysosomal degradation. However, endocytic trafficking of receptors often modulates their downstream signaling. We previously reported that internalization of PDGFRβ occurs via dynamin-dependent and -independent pathways but their further molecular determinants remained unknown. Here we show that, in human fibroblasts expressing endogenous PDGFRβ and stimulated with 50 ng/ml PDGF-BB, ligand-receptor uptake proceeds via the parallel routes of clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE). CME involves the canonical AP2 complex as a clathrin adaptor, while CIE requires RhoA-ROCK, Cdc42 and galectin-3, the latter indicating lectinmediated internalization via clathrin-independent carriers (CLICs). Although different uptake routes appear to be partly interdependent, they cannot fully substitute for each other. Strikingly, inhibition of any internalization mechanism impaired activation of STAT3 but not of other downstream effectors of PDGFRβ. Our data indicate that multiple routes of internalization of PDGFRβ contribute to a transcriptional and mitogenic response of cells to PDGF.

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Endocytic membrane turnover at the leading edge is driven by a transient interaction between Cdc42 and GRAF1

Cited by 33 publications

References 39 publications

Graf regulates hematopoiesis through GEEC endocytosis of EGFR

Graf regulates hematopoiesis through GEEC endocytosis of EGFR

Endocytic turnover of Rab8 controls cell polarization

Multiple routes of endocytic internalization of PDGFRβ contribute to PDGF-induced STAT3 signaling

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