Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dynamin II”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

Immunoreactivities of m-calpain, calpastatin, nitric oxide synthase, myelin basic protein and dynamin II in baker's yeast, wheat germ and lobster tail muscle.

Vertebrate m-calpain, calpastatin, constitutive nitric oxide synthase, myelin basic protein, and dynamin I are substrates of protein kinase C (PKC). The presence/absence of similar/related protein in nonvertebrate was investigated by immunological methods, including (1) affinity chromatography on agarose-secondary antibodies and agarose IgG for removal of nonspecific immunoreactivities from crude extracts; (2) omitting beta-mercaptoethanol treatment and boiling prior to SDS-PAGE to increase the immunoreactivity; (3) immunoreactivity comparisons of nonspecific IgG as controls with specific anti-(vertebrate PKC-substrates/related proteins) in Western blots. It was found that (a) m-calpain and dynamin I were absent in baker's yeast, wheat germ and lobster tail muscle, (b) m-calpain, nitric oxide synthase, myelin basic protein and dynamin II were present in all three samples, and (c) calpastatin was present in baker's yeast and lobster tail muscle. The presence and absence of these proteins suggest evolutionary conservation and divergence, respectively, of these PKC substrates.

Animals↗

Isolation of an ubiquitously expressed cDNA encoding human dynamin II, a member of the large GTP-binding protein family.

Dynamin (Dyn) is a member of a novel group of GTPases which was initially identified as a microtubule-binding protein with a role in vectorial movement. Three distinct Dyn-encoding genes (DYN I, II and III), with a neuronal-, ubiquitous or testis-specific expression, respectively, have been identified in rat. In man, only DYN I has so far been characterized. We have previously isolated a genomic DNA fragment implicated in the correction of mitomycin C hypersensitivity of cells from a Fanconi anemia patient belonging to genetic complementation group D (FA(D)). Using this probe, we have cloned a human complementary DNA designated hDYN II encoding a ubiquitous Dyn isoform. The predicted protein consists of 866 amino acids (97.5 kDa). Dyn proteins exhibit a high degree of evolutionary conservation: hDyn II is 98% identical to rat Dyn II and 73% identical to hDyn I. A unique 3.6-kb transcript is found in all human tissues examined and it is more abundant in skeletal muscle and heart. This transcript is also expressed in tissue-culture cells. The hDYN II message is present and not mutated in the FA(D) patient studied. In addition to the GTP-binding domain and motifs associated with regulatory function, the hDyn II protein contains a noticeable number of concensus motifs for p34Cdc2 kinase phosphorylation which may indicate a potential role at the G2/mitosis transition. The sequence reported here should allow a more complete analysis of Dyn function(s) in man.

Amino Acid Sequence↗

Phosphatidylinositol (4,5)-bisphosphate-dependent activation of dynamins I and II lacking the proline/arginine-rich domains.

Dynamins comprise a family of GTPases that participate in the early stages of endocytosis. The GTPase activity of neuronal specific dynamin I is stimulated by microtubules, negatively charged phospholipid vesicles, and Src homology 3-containing proteins, including Grb2. These activators were previously shown to bind to a proline/arginine-rich domain (PRD) in the carboxyl-terminal region of the enzyme. Dynamin II, which is ubiquitously expressed, had not been purified or characterized previously. In this study, the enzymatic properties of rat dynamin II and of D746, a dynamin II truncation mutant lacking the PRD, have been characterized. Dynamin II has a higher basal activity than dynamin I, but the two types of dynamin are stimulated similarly by microtubules, Grb2, and phospholipids. D746 is not activated by microtubules or Grb2, highlighting the significance of the PRD for these interactions, but it is activated by phospholipid vesicles containing phosphatidylserine or phosphatidylinositol-4,5- bisphosphate. Moreover, in contrast to previous reports, the PRD appears not to be required for phospholipid-stimulated self-assembly of dynamin, which is a key element in the regulation of its activity. Similar results were obtained with bovine brain dynamin I that had been subjected to limited proteolytic digestion to remove the PRD. Our data highlight the potential involvement of dynamin pleckstrin homology domains in the regulation of GTPase activity by phospholipids.

Animals↗

Profilin I attached to the Golgi is required for the formation of constitutive transport vesicles at the trans-Golgi network.

Profilin I was identified, by mass spectrometric sequencing and immunoblotting, as a component of purified Golgi cisternae from HepG2 cells. Binding to the Golgi was verified by indirect immunofluorescence in MT-1 cells showing that a fraction of profilin I colocalizes with TGN38, a marker of the trans-Golgi network (TGN). Studying the formation of constitutive exocytic vesicles at the TGN in a cell-free system demonstrated that cytosolic profilin I has no effect, while incubation of Golgi cisternae with a profilin I-specific antibody reduced vesicle formation by about 50%. Notably, the antibody displaces a fraction of the Golgi-bound dynamin II indicating that profilin I may indirectly promote vesicle formation by supporting the binding of dynamin II to the Golgi membrane. The impact of dynamin II on vesicle formation is demonstrated by incubating the Golgi with the proline-rich domain of dynamin II which concomitantly displaces dynamin II and inhibits vesicle formation. The data provide evidence that profilin I attaches to the Golgi apparatus and is required for the formation of constitutive transport vesicles.

Contractile Proteins↗

Characterization of Amoeba proteus myosin VI immunoanalog.

Amoeba proteus, the highly motile free-living unicellular organism, has been widely used as a model to study cell motility. However, molecular mechanisms underlying its unique locomotion and intracellular actin-based-only trafficking remain poorly understood. A search for myosin motors responsible for vesicular transport in these giant cells resulted in detection of 130-kDa protein interacting with several polyclonal antibodies against different tail regions of human and chicken myosin VI. This protein was binding to actin in the ATP-dependent manner, and immunoprecipitated with anti-myosin VI antibodies. In order to characterize its possible functions in vivo, its cellular distribution and colocalization with actin filaments and dynamin II during migration and pinocytosis were examined. In migrating amoebae, myosin VI immunoanalog localized to vesicular structures, particularly within the perinuclear and sub-plasma membrane areas, and colocalized with dynamin II immunoanalog and actin filaments. The colocalization was even more evident in pinocytotic cells as proteins concentrated within pinocytotic pseudopodia. Moreover, dynamin II and myosin VI immunoanalogs cosedimented with actin filaments, and were found on the same isolated vesicles. Blocking endogenous myosin VI immunoanalog with anti-myosin VI antibodies inhibited the rate of pseudopodia protrusion (about 19% decrease) and uroidal retraction (about 28% decrease) but did not affect cell morphology and the manner of cell migration. Treatment with anti-human dynamin II antibodies led to changes in directionality of amebae migration and affected the rate of only uroidal translocation (about 30% inhibition). These results indicate that myosin VI immunoanalog is expressed in protist Amoeba proteus and may be involved in vesicle translocation and cell locomotion.

Actins↗

Involvement of growth factor receptor-bound protein-2 in rat hepatocyte growth.

Growth factor receptor-bound protein-2 (GRB-2) is a protein linking receptor tyrosine kinase and Sos (Son of Sevenless gene; Ras GDP/GTP exchange protein), leading to activation of the Ras-mitogen-activated protein kinase (MAPK) cascade. So far, it remains unclear how GRB-2 plays a role in signal transduction pathways evoked by hepatotrophic factors. This study was attempted to evaluate the involvement of GRB-2 in signalling in rat hepatocyte growth. Using rat cultured hepatocytes stimulated by hepatotrophic factors and regenerating livers after partial hepatectomy (PH) we examined GRB-2-mediated linkage of hepatotrophic factor receptors to signal transducing molecules such as Sos or dynamin-II by immunoprecipitation and western blot analysis. In primary cultured hepatocytes stimulated with hepatocyte growth factor (HGF) or epidermal growth factor (EGF), GRB-2 linked HGF receptor or EGF receptor, respectively, to Sos which activated the mitogen-activated protein kinase (MAPK) cascade. In contrast, in primary cultured hepatocytes stimulated with insulin, GRB-2 linked insulin receptor substrate-1 (IRS-1) to dynamin-II as well as Sos. In the early phase after PH, GRB-2 activated the Ras-MAPK cascade by linking HGF receptor, IRS-1, or EGF receptor to Sos. In the late phase after PH, a complex of IRS-1-GRB-2 associated with dynamin-II, indicating that GRB-2 may transduce signals from IRS-1 to dynamin-II. We conclude that GRB-2 may play a role in transmitting signals from hepatotrophic factors to not only MAPK but also to other signalling pathways in hepatocyte growth.

Adaptor Proteins, Signal Transducing↗

Three dynamin-encoding genes are differentially expressed in developing rat brain.

Dynamin proteins are members of a recently described family of GTPases involved in receptor-mediated processes. To date, three different dynamin-encoding genes have been identified in mammalian tissues. Dynamin I is expressed only in neurons, whereas dynamin II is ubiquitously expressed. A third isoform, dynamin III, was originally isolated from a rat testis cDNA library and shown to be testis-specific. However, here we report the cloning and characterization of dynamin III from brain and lung, demonstrating a more extended pattern of expression for this isoform. In addition, we have investigated the temporal pattern of expression of these three genes during brain development. We find that both dynamin I and dynamin III mRNA levels are up-regulated during embryogenesis, whereas dynamin II mRNA levels remain unchanged. From these results, we conclude that dynamin III is not a testis-specific isoform and, furthermore, that rat brain expresses three different dynamin-encoding genes that are differentially regulated during development. Therefore, this large isoform diversity of dynamin proteins in brain predicts a significant complexity in the understanding of dynamin-based processes in this tissue.

Alternative Splicing↗

Actin depolymerization disrupts tight junctions via caveolae-mediated endocytosis.

The tight junction (TJ) determines epithelial barrier function. Actin depolymerization disrupts TJ structure and barrier function, but the mechanisms of this effect remain poorly understood. The goal of this study was to define these mechanisms. Madin-Darby canine kidney (MDCK) cells expressing enhanced green fluorescent protein-, enhanced yellow fluorescent protein-, or monomeric red fluorescent protein 1-fusion proteins of beta-actin, occludin, claudin-1, ZO-1, clathrin light chain A1, and caveolin-1 were imaged by time-lapse multidimensional fluorescence microscopy with simultaneous measurement of transepithelial electrical resistance (TER). Actin depolymerization was induced with latrunculin A (LatA). Within minutes of LatA addition TER began to fall. This coincided with occludin redistribution and internalization. In contrast, ZO-1 and claudin-1 redistribution occurred well after maximal TER loss. Occludin internalization and TER loss, but not actin depolymerization, were blocked at 14 degrees C, suggesting that membrane traffic is required for both events. Inhibition of membrane traffic with 0.4 M sucrose also blocked occludin internalization and TER loss. Internalized occludin colocalized with caveolin-1 and dynamin II, but not with clathrin, and internalization was blocked by dominant negative dynamin II (K44A), but not by Eps15Delta95-295 expression. Inhibition of caveolae-mediated endocytosis by cholesterol extraction prevented both LatA-induced TER loss and occludin internalization. Thus, LatA-induced actin depolymerization causes TJ structural and functional disruption by mechanisms that include caveolae-mediated endocytosis of TJ components.

Actins↗

The inhibitory gamma subunit of the type 6 retinal cyclic guanosine monophosphate phosphodiesterase is a novel intermediate regulating p42/p44 mitogen-activated protein kinase signaling in human embryonic kidney 293 cells.

The inhibitory gamma subunits of the retinal rod and cone photoreceptor type 6 retinal cyclic guanosine monophosphate phosphodiesterase (PDEgamma) are expressed in non-retinal tissues. Here, we show that PDEgamma interacts with the G-protein-coupled receptor kinase 2 signaling system to regulate the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase in human embryonic kidney 293 cells. This is based upon several lines of evidence. First, the transfection of cells with an antisense rod PDEgamma plasmid construct, which reduced endogenous rod PDEgamma expression, ablated the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase. Second, the transfection of cells with recombinant rod or cone PDEgamma and/or G-protein-coupled receptor kinase 2 increased the stimulation of p42/p44 mitogen-activated protein kinase by epidermal growth factor or thrombin. In contrast, a G-protein-coupled receptor kinase 2 phosphorylation-resistant rod PDEgamma mutant failed to increase the epidermal growth factor- or thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase and, in fact, functioned as a dominant negative. Thrombin also stimulated the association of endogenous rod PDEgamma with dynamin II, which was increased in cells transfected with rod PDEgamma or G-protein-coupled receptor kinase 2. Dynamin II plays a critical role in regulating endocytosis of receptor signal complexes required for activation of p42/p44 mitogen-activated protein kinase. Therefore, PDEgamma may have an important role in promoting endocytosis of receptor signal complexes leading to the activation of p42/p44 mitogen-activated protein kinase. We conclude that PDEgamma is an entirely novel intermediate regulating mitogenic signaling from both receptor tyrosine kinase and G-protein-coupled receptors in human embryonic kidney 293 cells.

3',5'-Cyclic-GMP Phosphodiesterases↗

Differential expression and regulation of multiple dynamins.

Dynamin is a GTP-, microtubule-, and phospholipid-binding protein that is expressed primarily in brain. In Drosophila, the shibire gene encodes a homologue of dynamin; mutations in this gene result in a defect in endocytosis, suggesting a function for dynamin in endocytic membrane traffic. In the present study we show that there are at least two distinct dynamin genes in mammals whose products are referred to as dynamins I and II. The two dynamins are similar to each other (79% identity) and are both equally homologous to the Drosophila shibire gene product (66% identity). The highest degree of identity between dynamins is observed in their N-terminal halves, whereas their C termini exhibit little homology. Transcripts of both dynamin genes are subject to at least two alternative splicing events, the first of which is identically found in both dynamins, whereas the second site of alternative splicing is different between the two types of dynamins. The first alternatively spliced sequence of the dynamins consists of an interior region that is present in two distinct but homologous forms in both dynamins, suggesting alternative use of exons in both genes at identical positions. The second site of alternative splicing results in the generation of different C termini in dynamin I and in the inclusion or exclusion of an interior four-amino acid sequence in dynamin II. The two dynamins exhibit remarkable differences in their tissue distribution and regulation. Dynamin I is almost exclusively expressed in the central nervous system. Conversely, dynamin II is expressed ubiquitously in all tissues tested. Previous studies revealed that the GTPase activity of dynamin I is regulated by phosphorylation by protein kinase C in nerve terminals. Expression of dynamins I and II by transfection in COS cells demonstrates that only dynamin I but not dynamin II is a substrate for protein kinase C. Our data suggest a specialization in the endocytic functions and the regulation of dynamins between neural and non-neural tissues in mammals.

Amino Acid Sequence↗

c-Src is involved in regulating signal transmission from PDGFbeta receptor-GPCR(s) complexes in mammalian cells.

We have reported that the platelet-derived growth factor receptor-beta (PDGFbeta) forms a novel signaling complex with G protein-coupled receptors (GPCR) (e.g. S1P(1) receptor) that enables more efficient activation of p42/p44 mitogen-activated protein kinase (MAPK) in response to PDGF and sphingosine 1-phosphate (S1P). We now demonstrate that c-Src participates in regulating the endocytosis of PDGFbeta receptor-GPCR complexes in response to PDGF. This leads to association of cytoplasmic p42/p44 MAPK with the receptor complex in endocytic vesicles. c-Src is regulated by G protein betagamma subunits and can interact with beta-arrestin. Indeed, the PDGF-dependent activation of p42/p44 MAPK was reduced by over-expression of the C-terminal domain of GRK2 (sequesters Gbetagamma subunits), the clathrin-binding domain of beta-arrestin and by inhibitors of c-Src and clathrin-mediated endocytosis. Moreover, PDGF and S1P induce the recruitment of c-Src to the PDGFbeta receptor-S1P(1) receptor complex. This leads to a G protein/c-Src-dependent tyrosine phosphorylation of Gab1 and accumulation of dynamin II at the plasma membrane, a step required for endocytosis of the PDGFbeta receptor-GPCR complex. These findings provide important information concerning the molecular organisation of novel receptor tyrosine kinase (RTK)-GPCR signal relays in mammalian cells.

Adaptor Proteins, Signal Transducing↗

Clathrin- and caveolin-1-independent endocytosis: entry of simian virus 40 into cells devoid of caveolae.

Simian Virus 40 (SV40) has been shown to enter host cells by caveolar endocytosis followed by transport via caveosomes to the endoplasmic reticulum (ER). Using a caveolin-1 (cav-1)-deficient cell line (human hepatoma 7) and embryonic fibroblasts from a cav-1 knockout mouse, we found that in the absence of caveolae, but also in wild-type embryonic fibroblasts, the virus exploits an alternative, cav-1-independent pathway. Internalization was rapid (t1/2 = 20 min) and cholesterol and tyrosine kinase dependent but independent of clathrin, dynamin II, and ARF6. The viruses were internalized in small, tight-fitting vesicles and transported to membrane-bounded, pH-neutral organelles similar to caveosomes but devoid of cav-1 and -2. The viruses were next transferred by microtubule-dependent vesicular transport to the ER, a step that was required for infectivity. Our results revealed the existence of a virus-activated endocytic pathway from the plasma membrane to the ER that involves neither clathrin nor caveolae and that can be activated also in the presence of cav-1.

ADP-Ribosylation Factor 6↗

Expression and protein-binding studies of the EEN gene family, new interacting partners for dynamin, synaptojanin and huntingtin proteins.

EEN, identified initially as a fusion partner to the mixed-lineage leukaemia gene in human leukaemia, and its related members, EEN-B1 and EEN-B2, have recently been shown to interact with two endocytic molecules, dynamin and synaptojanin, as well as with the huntingtin protein. In the present study, we show that the expression of the EEN gene-family members is differentially regulated. Multiple-spliced variants were identified for EEN-B2. In the brain, EEN-B1 and EEN-B2 mRNA are preferentially expressed in the cerebellar Purkinje and granule cells, dentate gyrus cells, hippocampal pyramidal neurons and cerebral granule cells. The expression patterns of EEN-B1 and EEN-B2 mRNA in the brain overlap with those of dynamin-I/III, synaptojanin-I and huntingtin, whereas the ubiquitous expression of EEN is consistent with that of dynamin-II. In testes, members of the EEN family are co-expressed with testis-type dynamin and huntingtin in Sertoli cells and germ cells respectively. Our results on the overlapping expression patterns are consistent with the proposed interaction of EEN family members with dynamin, synaptojanin and huntingtin protein in vivo. Although all three EEN family members bind to dynamin and synaptojanin, EEN-B1 has the highest affinity for binding, followed by EEN and EEN-B2. We also demonstrate that amphiphysin, a major synaptojanin-binding protein in brain, can compete with the EEN family for binding to synaptojanin and dynamin. We propose that recruitment of the EEN family by dynamin/synaptojanin to clathrin-coated pits can be regulated by amphiphysin.

Alternative Splicing↗

Ca(2+) influx inhibits dynamin and arrests synaptic vesicle endocytosis at the active zone.

Ca(2+) entry into nerve terminals through clusters of voltage-dependent Ca(2+) channels (VDCCs) at active zones creates a microdomain of elevated intracellular free Ca(2+) concentration ([Ca(2+)](i)) that stimulates exocytosis. We show that this VDCC-mediated [Ca(2+)](i) elevation has no specific role in stimulating endocytosis but can inhibit endocytosis evoked by three different methods in isolated mammalian nerve terminals. The inhibition can be relieved by using either VDCC antagonists or fast, but not slow, binding intracellular Ca(2+) chelators. The Ca(2+)-dependent inhibition of endocytosis is mimicked in vitro by a low-affinity inhibition of dynamin I vesiculation of phospholipids. Increased [Ca(2+)](i) also inhibits dynamin II GTPase activity and receptor-mediated endocytosis in non-neuronal cells. VDCC-meditated Ca(2+) entry inhibits dynamin-mediated endocytosis at the active zone and provides neurons with a mechanism to clear recycling vesicles to nonactive zone regions during periods of high activity.

Animals↗

Role of dynamin in the formation of transport vesicles from the trans-Golgi network.

Dynamin guanosine triphosphatases support the scission of clathrin-coated vesicles from the plasmalemma during endocytosis. By fluorescence microscopy of cultured rat hepatocytes, a green fluorescent protein-dynamin II fusion protein localized with clathrin-coated vesicles at the Golgi complex. A cell-free assay was utilized to demonstrate the role of dynamin in vesicle formation at the trans-Golgi. Addition of peptide-specific anti-dynamin antibodies to the assay mixture inhibited both constitutive exocytic and clathrin-coated vesicle formation. Immunodepletion of dynamin proteins also inhibited vesicle formation, and budding efficiency was restored upon readdition of purified dynamin. These data suggest that dynamin participates in the formation of distinct transport vesicles from the trans-Golgi network.

Adenosine Triphosphate↗

Dynamin-mediated internalization of caveolae.

The dynamins comprise an expanding family of ubiquitously expressed 100-kD GTPases that have been implicated in severing clathrin-coated pits during receptor-mediated endocytosis. Currently, it is unclear whether the different dynamin isoforms perform redundant functions or participate in distinct endocytic processes. To define the function of dynamin II in mammalian epithelial cells, we have generated and characterized peptide-specific antibodies to domains that either are unique to this isoform or conserved within the dynamin family. When microinjected into cultured hepatocytes these affinity-purified antibodies inhibited clathrin-mediated endocytosis and induced the formation of long plasmalemmal invaginations with attached clathrin-coated pits. In addition, clusters of distinct, nonclathrin-coated, flask-shaped invaginations resembling caveolae accumulated at the plasma membrane of antibody-injected cells. In support of this, caveola-mediated endocytosis of labeled cholera toxin B was inhibited in antibody-injected hepatocytes. Using immunoisolation techniques an anti-dynamin antibody isolated caveolar membranes directly from a hepatocyte postnuclear membrane fraction. Finally, double label immunofluorescence microscopy revealed a striking colocalization between dynamin and the caveolar coat protein caveolin. Thus, functional in vivo studies as well as ultrastructural and biochemical analyses indicate that dynamin mediates both clathrin-dependent endocytosis and the internalization of caveolae in mammalian cells.

Amino Acid Sequence↗

Expression and localisation of dynamin and syntaxin during neural development and neuromuscular synapse formation.

The expression and subcellular localisation of dynamin and syntaxin were examined during the periods of motor neuron development and neuromuscular synaptogenesis in the mouse embryo. Both dynamin and syntaxin could be detected by immunoblotting in the spinal cord at embryonic day 10 (E10; 2 days before axon outgrowth) and at all subsequent ages examined. Reverse transcription and polymerase chain reaction (RT-PCR) identified low levels of all three carboxy-terminal splicing forms of dynamin I in spinal cord from as early as E10. During the period of maturation of spinal neurons, from E10 to the first postnatal day (P0), the short carboxy-terminal splicing form of dynamin I (dynamin I*b) was up-regulated, as was dynamin III, relative to dynamin II mRNA. Syntaxin immunostaining became colocalized with the synaptic vesicle protein, SV2, at neuromuscular synapses within 12 hours of the commencement of synapse formation and throughout subsequent development. In contrast, dynamin, which is important for activity-dependent synaptic vesicle recycling and, thus, sustained neurotransmission, could not be detected at most newly formed synapses until several days after synapse formation. The delayed appearance of dynamin at the synapse, thus, heralds the neonatal development of robust synaptic transmission at the neuromuscular junction.

Animals↗

Local actin polymerization and dynamin recruitment in SV40-induced internalization of caveolae.

Simian virus 40 (SV40) utilizes endocytosis through caveolae for infectious entry into host cells. We found that after binding to caveolae, virus particles induced transient breakdown of actin stress fibers. Actin was then recruited to virus-loaded caveolae as actin patches that served as sites for actin "tail" formation. Dynamin II was also transiently recruited. These events depended on the presence of cholesterol and on the activation of tyrosine kinases that phosphorylated proteins in caveolae. They were necessary for formation of caveolae-derived endocytic vesicles and for infection of the cell. Thus, caveolar endocytosis is ligand-triggered and involves extensive rearrangement of the actin cytoskeleton.

Actin Cytoskeleton↗