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Journal of Cellular and Molecular... Aug 2008Frabin, together with, at least, FGD1, FGD2, FGD3 and FGD1-related Cdc42-GEF (FRG), is a member of a family of Cdc42-specific gua-nine nucleotide exchange factors... (Review)
Review
Frabin, together with, at least, FGD1, FGD2, FGD3 and FGD1-related Cdc42-GEF (FRG), is a member of a family of Cdc42-specific gua-nine nucleotide exchange factors (GEFs). These proteins have multiple phosphoinositide-binding domains, including two pleckstrin homology (PH) domains and an FYVE or FERM domain. It is likely that they couple the actin cytoskeleton with the plasma membrane. Frabin associates with a specific actin structure(s) and induces the direct activation of Cdc42 in the vicinity of this structure(s), resulting in actin reorganization. Furthermore, frabin associates with a specific membrane structure(s) and induces the indirect activation of Rac in the vicinity of this structure(s), resulting in the reorganization of the actin cytoskeleton. This reorganization of the actin cytoskeleton induces cell shape changes such as the formation of filopodia and lamellipodia.
Topics: Actins; Amino Acid Sequence; Animals; Cell Membrane; Cytoskeleton; Guanine Nucleotide Exchange Factors; Humans; Microfilament Proteins; Molecular Sequence Data; cdc42 GTP-Binding Protein
PubMed: 18410521
DOI: 10.1111/j.1582-4934.2008.00345.x -
Protein Science : a Publication of the... Jan 2015A subset of actin binding proteins is able to form crosslinks between two or more actin filaments, thus producing structures of parallel or networked bundles. These...
A subset of actin binding proteins is able to form crosslinks between two or more actin filaments, thus producing structures of parallel or networked bundles. These actin crosslinking proteins interact with actin through either bivalent binding or dimerization. We recently identified two binding sites within the actin binding domain of palladin, an actin crosslinking protein that plays an important role in normal cell adhesion and motility during wound healing and embryonic development. In this study, we show that actin induces dimerization of palladin. Furthermore, the extent of dimerization reflects earlier comparisons of actin binding and bundling between different domains of palladin. On the basis of these results we hypothesized that actin binding may promote a conformational change that results in dimerization of palladin, which in turn may drive the crosslinking of actin filaments. The proximal distance between two actin binding sites on crosslinking proteins determines the ultrastructural properties of the filament network, therefore we also explored interdomain interactions using a combination of chemical crosslinking experiments and actin cosedimentation assays. Limited proteolysis data reveals that palladin is less susceptible to enzyme digestion after actin binding. Our results suggest that domain movements in palladin are necessary for interactions with actin and are induced by interactions with actin filaments. Accordingly, we put forth a model linking the structural changes to functional dynamics.
Topics: Actin Cytoskeleton; Actins; Microfilament Proteins; Phosphoproteins; Protein Binding; Protein Conformation; Protein Multimerization; Protein Structure, Tertiary; Proteolysis; Recombinant Proteins
PubMed: 25307943
DOI: 10.1002/pro.2588 -
Trends in Neurosciences Nov 1989Dynamic alterations in the structure of the neuronal cytoskeleton are necessary for axonal growth and guidance during development and may also be involved in modulation... (Review)
Review
Dynamic alterations in the structure of the neuronal cytoskeleton are necessary for axonal growth and guidance during development and may also be involved in modulation of synaptic function. Recent evidence suggests that the structural and mechanochemical properties of the cytoskeletal protein, actin, are critical to our understanding of neuronal motility and cytoskeletal plasticity. Regulatory proteins that control actin polymerization, network organization and actin filament--membrane interactions have been described in non-neuronal and neuronal cell types. Many of these proteins are activated by increases in intracellular calcium. Recent results also suggest that receptor-mediated changes in polyphosphoinositide turnover may be involved in the control of cell structure. Interestingly, two major actin-binding proteins found in brain, gelsolin and profilin, specifically interact with phosphatidylinositol 4,5-bisphosphate, and may themselves play a role in regulating phosphoinositide turnover.
Topics: Actins; Animals; Calcium; Calcium-Binding Proteins; Contractile Proteins; Cytoskeleton; Gelsolin; Microfilament Proteins; Neurons; Phosphatidylinositol Phosphates; Phosphatidylinositols; Profilins
PubMed: 2479150
DOI: 10.1016/0166-2236(89)90098-2 -
Molecules (Basel, Switzerland) Oct 2020The ( and ) gene encodes multiple proteins, which together play crucial roles in modulating the assembly of the actin cytoskeleton. Splicing of the gene is complex,... (Review)
Review
The ( and ) gene encodes multiple proteins, which together play crucial roles in modulating the assembly of the actin cytoskeleton. Splicing of the gene is complex, with the two most studied TRIOBP protein isoforms sharing no overlapping amino acid sequence with each other. TRIOBP-1 (also known as TARA or TAP68) is a mainly structured protein that is ubiquitously expressed and binds to F-actin, preventing its depolymerization. It has been shown to be important for many processes including in the cell cycle, adhesion junctions, and neuronal differentiation. TRIOBP-1 has been implicated in schizophrenia through the formation of protein aggregates in the brain. In contrast, TRIOBP-4 is an entirely disordered protein with a highly specialized expression pattern. It is known to be crucial for the bundling of actin in the stereocilia of the inner ear, with mutations in it causing severe or profound hearing loss. Both of these isoforms are implicated in cancer. Additional longer isoforms of TRIOBP exist, which overlap with both TRIOBP-1 and 4. These appear to participate in the functions of both shorter isoforms, while also possessing unique functions in the inner ear. In this review, the structures and functions of all of these isoforms are discussed, with a view to understanding how they operate, both alone and in combination, to modulate actin and their consequences for human illness.
Topics: Actins; Amino Acid Sequence; Animals; Deafness; Humans; Mental Disorders; Microfilament Proteins; Neoplasms; Protein Isoforms; Protein Stability
PubMed: 33121024
DOI: 10.3390/molecules25214967 -
PLoS Biology Dec 2021Ischemic stroke is a major cause of death and long-term disability. We demonstrate that middle cerebral artery occlusion (MCAO) in mice leads to a strong decline in...
Ischemic stroke is a major cause of death and long-term disability. We demonstrate that middle cerebral artery occlusion (MCAO) in mice leads to a strong decline in dendritic arborization of penumbral neurons. These defects were subsequently repaired by an ipsilateral recovery process requiring the actin nucleator Cobl. Ischemic stroke and excitotoxicity, caused by calpain-mediated proteolysis, significantly reduced Cobl levels. In an apparently unique manner among excitotoxicity-affected proteins, this Cobl decline was rapidly restored by increased mRNA expression and Cobl then played a pivotal role in poststroke dendritic arbor repair in peri-infarct areas. In Cobl knockout (KO) mice, the dendritic repair window determined to span day 2 to 4 poststroke in wild-type (WT) strikingly passed without any dendritic regrowth. Instead, Cobl KO penumbral neurons of the primary motor cortex continued to show the dendritic impairments caused by stroke. Our results thereby highlight a powerful poststroke recovery process and identified causal molecular mechanisms critical during poststroke repair.
Topics: Actin Cytoskeleton; Actins; Animals; Cytoskeletal Proteins; Gene Expression; Infarction, Middle Cerebral Artery; Ischemic Stroke; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microfilament Proteins; Neuronal Plasticity; Neurons
PubMed: 34898601
DOI: 10.1371/journal.pbio.3001399 -
The Journal of Biological Chemistry Mar 2018Membrane phosphoinositides control organization and dynamics of the actin cytoskeleton by regulating the activities of several key actin-binding proteins. Twinfilin is...
Membrane phosphoinositides control organization and dynamics of the actin cytoskeleton by regulating the activities of several key actin-binding proteins. Twinfilin is an evolutionarily conserved protein that contributes to cytoskeletal dynamics by interacting with actin monomers, filaments, and the heterodimeric capping protein. Twinfilin also binds phosphoinositides, which inhibit its interactions with actin, but the underlying mechanism has remained unknown. Here, we show that the high-affinity binding site of twinfilin for phosphoinositides is located at the C-terminal tail region, whereas the two actin-depolymerizing factor (ADF)/cofilin-like ADF homology domains of twinfilin bind phosphoinositides only with low affinity. Mutagenesis and biochemical experiments combined with atomistic molecular dynamics simulations reveal that the C-terminal tail of twinfilin interacts with membranes through a multivalent electrostatic interaction with a preference toward phosphatidylinositol 3,5-bisphosphate (PI(3,5)P), PI(4,5)P, and PI(3,4,5)P This initial interaction places the actin-binding ADF homology domains of twinfilin in close proximity to the membrane and subsequently promotes their association with the membrane, thus leading to inhibition of the actin interactions. In support of this model, a twinfilin mutant lacking the C-terminal tail inhibits actin filament assembly in a phosphoinositide-insensitive manner. Our mutagenesis data also reveal that the phosphoinositide- and capping protein-binding sites overlap in the C-terminal tail of twinfilin, suggesting that phosphoinositide binding additionally inhibits the interactions of twinfilin with the heterodimeric capping protein. The results demonstrate that the conserved C-terminal tail of twinfilin is a multifunctional binding motif, which is crucial for interaction with the heterodimeric capping protein and for tethering twinfilin to phosphoinositide-rich membranes.
Topics: Amino Acid Motifs; Animals; Mice; Microfilament Proteins; Models, Chemical; Molecular Dynamics Simulation; Phosphatidylinositols; Protein Domains
PubMed: 29425097
DOI: 10.1074/jbc.RA117.000484 -
Molecular Biology of the Cell Nov 2016We used in vivo and in vitro strategies to study the mechanisms of multivesicular endosome biogenesis. We found that, whereas annexinA2 and ARP2/3 mediate F-actin...
We used in vivo and in vitro strategies to study the mechanisms of multivesicular endosome biogenesis. We found that, whereas annexinA2 and ARP2/3 mediate F-actin nucleation and branching, respectively, the ERM protein moesin supports the formation of F-actin networks on early endosomes. We also found that moesin plays no role during endocytosis and recycling to the plasma membrane but is absolutely required, much like actin, for early-to-late-endosome transport and multivesicular endosome formation. Both actin network formation in vitro and early-to-late endosome transport in vivo also depend on the F-actin-binding protein cortactin. Our data thus show that moesin and cortactin are necessary for formation of F-actin networks that mediate endosome biogenesis or maturation and transport through the degradative pathway. We propose that the primary function of endosomal F-actin is to control the membrane remodeling that accompanies endosome biogenesis. We also speculate that this mechanism helps segregate tubular and multivesicular membranes along the recycling and degradation pathways, respectively.
Topics: Actin Cytoskeleton; Actins; Carrier Proteins; Cell Membrane; Cortactin; Endocytosis; Endosomes; HeLa Cells; Humans; Microfilament Proteins; Protein Binding; Protein Transport
PubMed: 27605702
DOI: 10.1091/mbc.E15-12-0853 -
The Journal of Cell Biology Aug 2001Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals.... (Review)
Review
Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals. Abp1p, a yeast protein involved in endocytosis, and cortactin, a mammalian src substrate, both enhance the ability of the Arp2/3 complex to assemble branched actin filament networks.
Topics: Actin Cytoskeleton; Actin-Related Protein 2; Actin-Related Protein 3; Actins; Cytoskeletal Proteins; Endocytosis; Fungal Proteins; Microfilament Proteins; Models, Biological; Protein Binding; Saccharomyces cerevisiae Proteins; Signal Transduction
PubMed: 11514584
DOI: 10.1083/jcb.200105061 -
The Journal of Biological Chemistry Sep 2001In many cases, the biologic responses of cells to extracellular signals and the specificity of the responses cannot be explained solely on the basis of the interactions...
In many cases, the biologic responses of cells to extracellular signals and the specificity of the responses cannot be explained solely on the basis of the interactions of known signaling proteins. Recently, scaffolding and adaptor proteins have been identified that organize signaling proteins in cells and that contribute to the nature and specificity of signaling pathways. In an effort to identify proteins that might organize the signaling system(s) activated by the extracellular Ca(2+) receptor (CaR), we used a bait construct representing the intracellular C terminus of the human CaR and the yeast two hybrid system to screen a human kidney cDNA library. We identified a clone representing the C-terminal 1042 amino acids (aa) of the cytoskeletal protein filamin (ABP-280). Analysis of truncation and deletion constructs of the CaR C terminus and the filamin cDNA clone demonstrated that the CaR and filamin interact via regions containing aa 907-997 of the CaR C terminus and aa 1566-1875 of filamin. Interaction of the two proteins in mammalian HEK-293 cells was demonstrated by co-immunoprecipitation and colocalization of them using immunofluorescence microscopy. The functional importance of their interaction was documented by transiently expressing the CaR in M2 melanoma cells that lack filamin, or in A7 melanoma cells that stably express filamin, and demonstrating that the CaR activated ERK only in the presence of filamin. Co-expression of the CaR with a peptide derived from the region of the CaR C terminus that interacts with filamin reduced the ability of the CaR to activate p42ERK in a dose-dependent manner, but did not inhibit the ability of the ET(A) receptor to activate ERK. The fact that filamin interacts with the CaR and other cell signaling proteins including mitogen-activated protein kinases and small GTPases, indicates that it may act as a scaffolding protein to organize cell signaling systems involving the CaR.
Topics: Amino Acid Sequence; Contractile Proteins; Filamins; Humans; Immunohistochemistry; Microfilament Proteins; Mitogen-Activated Protein Kinases; Molecular Sequence Data; Receptors, Calcium-Sensing; Receptors, Cell Surface
PubMed: 11390379
DOI: 10.1074/jbc.M100775200 -
Molecular Biology of the Cell Feb 2012Clathrin-mediated endocytosis involves a coordinated series of molecular events regulated by interactions among a variety of proteins and lipids through specific...
Clathrin-mediated endocytosis involves a coordinated series of molecular events regulated by interactions among a variety of proteins and lipids through specific domains. One such domain is the Eps15 homology (EH) domain, a highly conserved protein-protein interaction domain present in a number of proteins distributed from yeast to mammals. Several lines of evidence suggest that the yeast EH domain-containing proteins Pan1p, End3p, and Ede1p play important roles during endocytosis. Although genetic and cell-biological studies of these proteins suggested a role for the EH domains in clathrin-mediated endocytosis, it was unclear how they regulate clathrin coat assembly. To explore the role of the EH domain in yeast endocytosis, we mutated those of Pan1p, End3p, or Ede1p, respectively, and examined the effects of single, double, or triple mutation on clathrin coat assembly. We found that mutations of the EH domain caused a defect of cargo internalization and a delay of clathrin coat assembly but had no effect on assembly of the actin patch. We also demonstrated functional redundancy among the EH domains of Pan1p, End3p, and Ede1p for endocytosis. Of interest, the dynamics of several endocytic proteins were differentially affected by various EH domain mutations, suggesting functional diversity of each EH domain.
Topics: Actins; Amino Acid Sequence; Clathrin; Conserved Sequence; Cytoskeletal Proteins; Endocytosis; Microfilament Proteins; Molecular Sequence Data; Mutation; Protein Interaction Domains and Motifs; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 22190739
DOI: 10.1091/mbc.E11-04-0380