Eps8, Arp2/3 and IRSp53 in TNT formation
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Q Exactive
ORGANISM(S): Mus Musculus (mouse)
SUBMITTER: 
MARIETTE MATONDO
LAB HEAD: Michael Henderson
PROVIDER: PXD034649 | Pride | 2023-11-27
REPOSITORIES: Pride
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Project description:Tunneling nanotubes (TNTs) connect distant cells and mediate cargo transfer for intercellular communication in physiological and pathological contexts. How the cell controls a common pool of proteins to generate these actin-mediated protrusions spanning length scales beyond those attainable by canonical filopodia remains unknown. Through a combination of surface micropatterning, microscopy and optical tweezer-based approaches, we found that Arp2/3-dependent pathways attenuate the extent with which actin polymerizes in nanotubes, limiting the formation and attainable lengths of TNTs. Upon Arp2/3 inhibition Epidermal growth factor receptor kinase substrate 8 (Eps8) exhibited heightened interactions with the inverted Bin/Amphiphysin/Rvs (I-BAR) domain protein IRSp53 resulting in increased TNTs. In these conditions, Eps8 interaction with proteins enhancing filament turnover and depolymerization were reduced. Our data reveals how common players in protrusions (Eps8 and IRSp53) drive outward linear actin extension to form TNTs, and that their interaction is enhanced when competing pathways overutilizing actin in branched Arp2/3 networks are inhibited, suggesting a shift in the equilibrium (and proteins usage) between branched and linear actin polymerization to form different cell protrusions.
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Project description:Development and homeostasis of blood vessels critically depend on the regulation of endothelial cell-cell junctions. Perturbations in cell-cell junction organization and function results in developmental defects and vascular pathologies including chronic inflammation, edema and atherosclerosis. Although many aspects of blood vessel formation and homeostasis depend on cell-cell junctions, the molecular mechanisms that regulate their dynamic rearrangement are not fully understood. The VEcad-catenin complex, which constitute the molecular basis of the adherens junctions (AJ), is connected to the actin cytoskeleton and its function is regulated by cytoskeletal contraction and actin-driven plasma membrane protrusions. Junction-associated intermitted lamellipodia (JAIL) are small actin-driven protrusions at cell-cell junctions controlled by the actin related protein 2/3 (Arp2/3)-complex that contribute to the regulation of cell-cell junctions. JAIL drive VEcad dynamics within the cell-cell junction thereby being critical for monolayer integrity, cell migration and angiogenesis. The molecular mechanisms regulating JAIL during vessel development are not completely understood. Coronin 1B (Coro1B) is an actin binding protein that controls actin networks at classical lamellipodia via both Arp2/3 complex and cofilin-mediated pathways. The role of Coro1B in endothelial cell (ECs) is not fully understood. In this study we demonstrate that Coro1B is a novel component and regulator of cell-cell junctions in ECs. Immunofluorescence studies show that Coro1B colocalizes with VEcad at cell-cell junctions in monolayers of ECs. Live-cell imaging reveal that Coro1B is recruited to, and operated at, actin-driven membrane protrusions at the cell-cell junctions. Coro1B recruitment to cell-cell junctions is regulated by cytoskeleton tension. By analyzing the Coro1B interactome, we identify integrin linked kinase (ILK) as new Coro1B-associated protein. Coro1B colocalizes with α-parvin, an interactor of ILK, at the leading edge of lamellipodia protrusions. Finally, functional experiments reveal that depletion of Coro1B causes defects in actin cytoskeleton and cell-cell junctions. In matrigel vessel network assays, depletion of Coro1B results in reduced network complexity, vessel number and vessel length. Together, our findings point towards a critical role for Coro1B in the dynamic remodeling of endothelial cell-cell junction and the assembly of vessel network.
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Project description:Arp2/3 complex assembles branched actin filaments key to many cellular processes, but its organismal roles remain poorly understood. Here we employed conditional arpc4 knockout mice to study the function of the Arp2/3 complex in the epidermis.We found that depletion of the Arp2/3 complex by knockout of arpc4 results in skin abnormalities at birth that evolve into a severe psoriasis-like disease hallmarked by hyperactivation of transcription factor Nrf2. Knockout of arpc4 in cultured keratinocytes was sufficient to induce nuclear accumulation of Nrf2, upregulation of Nrf2-target genes and decreased filamentous actin levels. Furthermore, pharmacological inhibition of the Arp2/3 complex unmasked the role of branched actin filaments in Nrf2 regulation. Consistently, we unveiled that Nrf2 associates with the actin cytoskeleton in cells and binds to filamentous actin in vitro Finally, we discovered that Arpc4 is downregulated in both human and mouse psoriatic epidermis. Thus, the Arp2/3 complex affects keratinocytes' shape and transcriptome through an actin-based cell-autonomous mechanism that influences epidermal morphogenesis and homeostasis.
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Project description:Arp2/3 complex assembles branched actin filaments key to many cellular processes, but its organismal roles remain poorly understood. Here we employed conditional arpc4 knockout mice to study the function of the Arp2/3 complex in the epidermis.We found that depletion of the Arp2/3 complex by knockout of arpc4 results in skin abnormalities at birth that evolve into a severe psoriasis-like disease hallmarked by hyperactivation of transcription factor Nrf2. Knockout of arpc4 in cultured keratinocytes was sufficient to induce nuclear accumulation of Nrf2, upregulation of Nrf2-target genes and decreased filamentous actin levels. Furthermore, pharmacological inhibition of the Arp2/3 complex unmasked the role of branched actin filaments in Nrf2 regulation. Consistently, we unveiled that Nrf2 associates with the actin cytoskeleton in cells and binds to filamentous actin in vitro Finally, we discovered that Arpc4 is downregulated in both human and mouse psoriatic epidermis. Thus, the Arp2/3 complex affects keratinocytes' shape and transcriptome through an actin-based cell-autonomous mechanism that influences epidermal morphogenesis and homeostasis.
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Project description:Candida albicans is a diploid fungal pathogen lacking a defined complete sexual cycle, and thus has been refractory to standard forward genetic analysis. Instead, transcription profiling and reverse genetic strategies based on Saccharomyces cerevisiae have typically been used to link genes to functions. To overcome restrictions inherent in such indirect approaches, we have investigated a forward genetic mutagenesis strategy based on the UAU1 technology. We screened 4700 random insertion mutants for defects in hyphal development, and linked two new genes (ARP2 and VPS52) to hyphal growth. Deleting ARP2 abolished hyphal formation, generated round and swollen yeast phase cells, disrupted cortical actin patches and blocked virulence in mice. The mutants also showed a global lack of induction of hyphae-specific genes upon the yeast-to-hyphae switch. Surprisingly, both arp2Î/Î and arp2Î/Îarp3Î/Î mutants were still able to endocytose FM4-64 and Lucifer Yellow, although as shown by time-lapse movies internalization of FM4-64 was somewhat delayed in mutant cells. Thus the non-essential role of the Arp2/3 complex discovered by forward genetic screening in C. albicans showed that uptake of membrane components from the plasma membrane to vacuolar structures is not dependent on this actin nucleating machinery. By forward genetic screening, we have identified genes that are essential for hyphal formation. One of the hits is the Arp2/3 complex, which is essential for hyphal formation, but not for viability in Candida albicans. To gain insights into cellular processes affected by disrupting Arp2/3 complex functions, we performed transcriptional profiling under yeast growth conditions (YPD at 30°C for three hours) or hyphal induction (YPD + 10% FBS at 37°C for three hours) and compared transcriptional consequences of deleting ARP2 to MYO5 and SLA2 microarray data sets (Oberholzer et al., 2006).
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Project description:Oncogenic KrasG12D, a driver mutation of pancreatic ductal adenocarcinoma (PDAC), induces neoplastic transformation of acinar cells through acinar-to-ductal metaplasia (ADM). Here, we show that both functional complexes of mTOR (mechanistic target of rapamycin kinase, mTORC1 and mTORC2) are specifically activated in ADM. Murine models uncover that mTORC1 and mTORC2 cooperate to promote KrasG12D-driven ADM development. Proteomic analyses identify Arp2/3 complex, an actin nucleator, as the common downstream effector: mTORC1 is responsible for the protein synthesis of Rac1 and Arp3 while mTORC2 promotes the Arp2/3 complex activity via Akt/Rac1 signalling. Genetic ablation of Arp2/3 complex completely arrests KrasG12D-driven ADM development. The Arp2/3 complex-mediated y-branching of actin network promotes the basolateral spread of filamentous actin, which is indispensable for acinar cells-initiated carcinogenesis. Induced by oncogenic KrasG12D, ADM is a metaplastic phenotype of acinar cells that requires extensive actin rearrangements. mTORC1 and mTORC2, downstream targets of KrasG12D, have well-established oncogenic functions in PDAC development. The actin-related protein 2/3 (Arp2/3) complex is the first identified actin nucleator. Regarded as textbook knowledge, it is activated by EGFR/Rac1 signalling to promote the polymerisation of branched actin filaments from pre-existing filaments in numerous biological contexts. Hereby, we identify that mTORC1 and mTORC2 attain a dual, yet non-redundant, regulatory role in promoting Arp2/3 complex function, which is responsible for generating basolateral filamentous actin in ADM. Thus, the role of Arp2/3 complex fills up the missing gap between putative oncogenic signals and actin dynamics underlying PDAC initiation.
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2022-02-16 | PXD011013 | Pride
Project description:Intercellular communication within the bone marrow niche significantly influences leukemogenesis and the sensitivity of leukemic cells to therapy. However, the landscape of possible cell-cell interactions is still incomplete. Tunneling nanotubes (TNTs) are a novel mode of intercellular cross-talk. They are long, thin membranous conduits that enable the direct transfer of various cargo between cells. The present study found that TNTs are formed between leukemic and bone marrow stromal cells. Confocal three-dimensional reconstructions, correlative light-electron microscopy, and electron tomography provided evidence that TNTs transfer cellular vesicles between cells. The quantitative analysis demonstrated the stimulation of TNT-mediated vesicle transfer from stromal cells to leukemic cells by the stromal component. The vesicular cargo that was received from stroma cells conferred resistance to anti-leukemic treatment. Moreover, specific sets of proteins with a potential role in survival and the drug response were transferred within these vesicles. Altogether, we found that TNTs are involved in a novel and potent mechanism that participates in leukemia-stroma cross-talk and the stroma-mediated cytoprotection of leukemic cells. Our findings implicate TNT connections as a possible target for therapeutic interventions within the leukemia microenvironment to attenuate stroma-conferred protection.
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