Filamin a binds to CCR2B and regulates its internalization.
Ontology highlight
ABSTRACT:
SUBMITTER: Minsaas L
PROVIDER: S-EPMC2923182 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Transcytosis via caveolae is critical for maintaining vascular homeostasis by regulating the tissue delivery of macromolecules, hormones, and lipids. In the present study, we test the hypothesis that interactions between F-actin cross-linking protein filamin A and caveolin-1 facilitate the internalization and trafficking of caveolae. Small interfering RNA-mediated knockdown of filamin A, but not filamin B, reduced the uptake and transcytosis of albumin by approximately 35 and 60%, respectively, without altering the actin cytoskeletal structure or cell-cell adherens junctions. Mobility of both intracellular caveolin-1-green fluorescent protein (GFP)-labeled vesicles measured by fluorescence recovery after photobleaching and membrane-associated vesicles measured by total internal reflection-fluorescence microscopy was decreased in cells with reduced filamin A expression. In addition, in melanoma cells that lack filamin A (M2 cells), the majority of caveolin-1-GFP was localized on the plasma membrane, whereas in cells in which filamin A expression was reconstituted (A7 cells and M2 cells transfected with filamin A-RFP), caveolin-1-GFP was concentrated in intracellular vesicles. Filamin A association with caveolin-1 in endothelial cells was confirmed by cofractionation of these proteins in density gradients, as well as by coimmunoprecipitation. Moreover, this interaction was enhanced by Src activation, associated with increased caveolin-1 phosphorylation, and blocked by Src inhibition. Taken together, these data suggest that filamin A association with caveolin-1 promotes caveolae-mediated transport by regulating vesicle internalization, clustering, and trafficking.
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Project description:Periventricular heterotopia (PVH) is a congenital malformation of human cerebral cortex frequently associated with Filamin-A (FLN-A) mutations but the pathogenetic mechanisms remain unclear. Here, we show that the MEKK4 (MAP3K4) pathway is involved in Fln-A regulation and PVH formation. MEKK4(-/-) mice developed PVH associated with breaches in the neuroependymal lining which were largely comprised of neurons that failed to reach the cortical plate. RNA interference (RNAi) targeting MEKK4 also impaired neuronal migration. Expression of Fln was elevated in MEKK4(-/-) forebrain, most notably near sites of failed neuronal migration. Importantly, recombinant MKK4 protein precipitated a complex containing MEKK4 and Fln-A, and MKK4 mediated signaling between MEKK4 and Fln-A, suggesting that MKK4 may bridge these molecules during development. Finally, we showed that wild-type FLN-A overexpression inhibited neuronal migration. Collectively, our results demonstrate a link between MEKK4 and Fln-A that impacts neuronal migration initiation and provides insight into the pathogenesis of human PVH.
| S-EPMC1876745 | biostudies-literature
Project description:Among the three isoforms encoded by Rtn4, Nogo-A has been intensely investigated as a central nervous system inhibitor. Although Nogo-A expression is increased in muscles of patients with amyotrophic lateral sclerosis, its role in muscle homeostasis and regeneration is not well elucidated. In this study, we discovered a significant increase in Nogo-A expression in various muscle-related pathological conditions. Nogo-/- mice displayed dystrophic muscle structure, dysregulated muscle regeneration following injury, and altered gene expression involving lipid storage and muscle cell differentiation. We hypothesized that increased Nogo-A levels might regulate muscle regeneration. Differentiating myoblasts exhibited Nogo-A upregulation and silencing Nogo-A abrogated myoblast differentiation. Nogo-A interacted with filamin-C, suggesting a role for Nogo-A in cytoskeletal arrangement during myogenesis. In conclusion, Nogo-A maintains muscle homeostasis and integrity, and pathologically altered Nogo-A expression mediates muscle regeneration, suggesting Nogo-A as a novel target for the treatment of myopathies in clinical settings.
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Project description:Actin assembly and dynamics control the shape, motility and functions of diverse cell types. Programme for controlling theses dynamics is hard-coded into actin binding proteins and regulatory proteins. Refilins (RefilinA and RefilinB) are short lived regulatory proteins that interact with the actin-binding protein Filamin to convert it from an actin branching protein into one that bundles. We here show that different mechanisms converge to increase Refilin level in brain NG2+ precursor cells (polydendrocytes) committed to differentiate into the oligodendrocyte lineage. RefilinA is up-regulated through transcriptional activation during commitment into oligodendrocyte progenitor cells (OPC). RefilinB expression relies on PDGF signalling and is further stabilized by a unique auto-inhibitory domain masking the adjacent conserved PEST degradation signal. In NG2+ precursor cells and OPC, the RefilinB/Filamin complex localizes on filipodia protrusions and filipodial processes. Stable ectopic expression of Refilins in cells stimulates membrane remodelling dynamics linked with filipodia growth. These studies extend the function of the Refilin/FLNA complex to cell membrane remodelling linked with reorganization of underlying actin cytoskeleton. We performed whole transcriptomic analysis on the three cell population derived from OPC cells. Three different cultures were done and for each experiment we compared each cell population (NG2+, NG2+/A2B5 and O4) to the other 2 cell populations.
2013-05-01 | E-GEOD-37600 | biostudies-arrayexpress
Project description:Filamin A (FLNA) is an integrator of cell mechanics and signaling. The spreading and migration observed in FLNA sufficient A7 melanoma cells but not in the parental FLNA deficient M2 cells have been attributed to FLNA. In A7 and M2 cells, the normal prion (PrP) exists as pro-PrP, retaining its glycosylphosphatidyl-inositol (GPI) anchor peptide signal sequence (GPI-PSS). The GPI-PSS of PrP has a FLNA binding motif and binds FLNA. Reducing PrP expression in A7 cells alters the spatial distribution of FLNA and organization of actin and diminishes cell spreading and migration. Integrin ?1 also binds FLNA. In A7 cells, FLNA, PrP, and integrin ?1 exist as two independent, yet functionally linked, complexes; they are FLNA with PrP or FLNA with integrin ?1. Reducing PrP expression in A7 cells decreases the amount of integrin ?1 bound to FLNA. A PrP GPI-PSS synthetic peptide that crosses the cell membrane inhibits A7 cell spreading and migration. Thus, in A7 cells FLNA does not act alone; the binding of pro-PrP enhances association between FLNA and integrin ?1, which then promotes cell spreading and migration. Pro-PrP is detected in melanoma in situ but not in melanocyte. Invasive melanoma has more pro-PrP. The binding of pro-PrP to FLNA, therefore, contributes to melanomagenesis.
| S-EPMC2943319 | biostudies-literature
Project description:Humans who harbor loss of function mutations in the actin-associated filamin B (FLNB) gene develop spondylocarpotarsal syndrome (SCT), a disorder characterized by dwarfism (delayed bone formation) and premature fusion of the vertebral, carpal and tarsal bones (premature differentiation). To better understand the cellular and molecular mechanisms governing these seemingly divergent processes, we generated and characterized FlnB knockdown ATDC5 cell lines. We found that FlnB knockdown led to reduced proliferation and enhanced differentiation in chondrocytes. Within the shortened growth plate of postnatal FlnB(-/-) mice long bone, we observed a similarly progressive decline in the number of rapidly proliferating chondrocytes and premature differentiation characterized by an enlarged prehypertrophic zone, a widened Col2a1(+)/Col10a1(+) overlapping region, but relatively reduced hypertrophic zone length. The reduced chondrocyte proliferation and premature differentiation were, in part, attributable to enhanced G2/M phase progression, where fewer FlnB deficient ATDC5 chondrocytes resided in the G2/M phase of the cell cycle. FlnB loss reduced Cdk1 phosphorylation (an inhibitor of G2/M phase progression) and Cdk1 inhibition in chondrocytes mimicked the null FlnB, premature differentiation phenotype, through a β1-integrin receptor- Pi3k/Akt (a key regulator of chondrocyte differentiation) mediated pathway. In this context, the early prehypertrophic differentiation provides an explanation for the premature differentiation seen in this disorder, whereas the progressive decline in proliferating chondrocytes would ultimately lead to reduced chondrocyte production and shortened bone length. These findings begin to define a role for filamin proteins in directing both cell proliferation and differentiation through indirect regulation of cell cycle associated proteins.
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Project description:Interaction between the cytoplasmic domain of GPIbα with its cytoskeletal binding partner, filamin, is a major determinant of platelet size, and deficiency of either protein results in macrothrombocytopenia. To clarify the mechanism by which GPIbα-filamin interactions regulate platelet production, we manipulated the expression levels of filamin and GPIb in cultured embryonic stem cells (ESCs) that were subsequently differentiated into platelets. Knocking down filamins A and B resulted in the production of ESC-derived proplatelets with abnormally large swellings and proplatelet shafts that generated giant platelets in culture. Large platelets could also be generated by overexpressing GPIbα in ESCs, or by overexpressing in vivo a transgene encoding a chimeric protein containing the cytoplasmic domain of GPIbα. To identify the mechanism by which the GPIb:filamin ratio regulates platelet size, we manipulated filamin and GPIbα levels in HEK293T cells and examined the effects of overexpressing either protein on their ability to traffic to the cell periphery. Accumulation of either protein within the endoplasmic reticulum resulted in trapping of the other. Taken together, these data demonstrate that coordinated expression of GPIbα and filamin is required for efficient trafficking of either protein to the cell surface, and for production of normal-sized platelets.
| S-EPMC3327465 | biostudies-literature
Project description:Actin assembly and dynamics control the shape, motility and functions of diverse cell types. Programme for controlling theses dynamics is hard-coded into actin binding proteins and regulatory proteins. Refilins (RefilinA and RefilinB) are short lived regulatory proteins that interact with the actin-binding protein Filamin to convert it from an actin branching protein into one that bundles. We here show that different mechanisms converge to increase Refilin level in brain NG2+ precursor cells (polydendrocytes) committed to differentiate into the oligodendrocyte lineage. RefilinA is up-regulated through transcriptional activation during commitment into oligodendrocyte progenitor cells (OPC). RefilinB expression relies on PDGF signalling and is further stabilized by a unique auto-inhibitory domain masking the adjacent conserved PEST degradation signal. In NG2+ precursor cells and OPC, the RefilinB/Filamin complex localizes on filipodia protrusions and filipodial processes. Stable ectopic expression of Refilins in cells stimulates membrane remodelling dynamics linked with filipodia growth. These studies extend the function of the Refilin/FLNA complex to cell membrane remodelling linked with reorganization of underlying actin cytoskeleton.
2013-05-01 | GSE37600 | GEO
Project description:Mice lacking pituitary adenylate cyclase-activating polypeptide (PACAP) display psychomotor abnormalities, most of which are ameliorated by atypical antipsychotics with serotonin (5-HT) 2A receptor (5-HT2A) antagonism. Heterozygous Pacap mutant mice show a significantly higher hallucinogenic response than wild-type mice to a 5-HT2A agonist. Endogenous PACAP may, therefore, affect 5-HT2A signaling; however, the underlying neurobiological mechanism for this remains unclear. Here, we examined whether PACAP modulates 5-HT2A signaling by addressing cellular protein localization. PACAP induced an increase in internalization of 5-HT2A but not 5-HT1A, 5-HT2C, dopamine D2 receptors or metabotropic glutamate receptor 2 in HEK293T cells. This PACAP action was inhibited by protein kinase C inhibitors, β-arrestin2 silencing, the PACAP receptor PAC1 antagonist PACAP6-38, and PAC1 silencing. In addition, the levels of endogenous 5-HT2A were decreased on the cell surface of primary cultured cortical neurons after PACAP stimulation and were increased in frontal cortex cell membranes of Pacap-/- mice. Finally, intracerebroventricular PACAP administration suppressed 5-HT2A agonist-induced head twitch responses in mice. These results suggest that PACAP-PAC1 signaling increases 5-HT2A internalization resulting in attenuation of 5-HT2A-mediated signaling, although further study is necessary to determine the relationship between behavioral abnormalities in Pacap-/- mice and PACAP-induced 5-HT2A internalization.
| S-EPMC8574227 | biostudies-literature
Project description:This study tested the hypothesis that the IFN-? R1 287-YVSLI-91 intracellular motif regulates its endocytosis. IFN-? exerts its biological activities by interacting with a specific cell-surface RC composed of two IFN-? R1 and two IFN-? R2 chains. Following IFN-? binding and along with the initiation of signal transduction, the ligand and IFN-? R1 are internalized. Two major types of consensus-sorting signals are described in receptors, which are rapidly internalized from the plasma membrane to intracellular compartments: tyrosine-based and dileucine-based internalization motifs. Transfection of HEK 293 cells and IFN-? R1-deficient fibroblasts with WT and site-directed, mutagenesis-generated mutant IFN-? R1 expression vectors helped us to identify region IFN-? R1 287-YVSLI-291 as the critical domain required for IFN-?-induced IFN-? R1 internalization and Y287 and LI290-291 as part of a common structure essential for receptor endocytosis and function. This new endocytosis motif, YxxLI, shares characteristics of tyrosine-based and dileucine-based internalization motifs and is highly conserved in IFN-? Rs across species. The IFN-? R1 270-LI-271 dileucine motif, previously thought to be involved in this receptor endocytosis, showed to be unnecessary for receptor endocytosis.
| S-EPMC3395421 | biostudies-literature