Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pleckstrin homology (PH) domains are found in numerous membrane-associated proteins and have been implicated in the mediation of protein-protein and protein-phospholipid interactions. Dynamin, a GTPase required for clathrin-dependent endocytosis, contains a PH domain which binds to phosphoinositides and participates in the interaction between dynamin and the betagamma subunits of heterotrimeric G proteins. The PH domain is essential for expression of phosphoinositide-stimulated GTPase activity of dynamin in vitro, but its involvement in the endocytic process is unknown. We expressed a series of dynamin PH domain mutants in cultured cells and determined their effect on transferrin uptake by those cells. Endocytosis is blocked in cells expressing a PH domain deletion mutant and a point mutant that fails to interact with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. In contrast, expression of a point mutant with unimpaired PI(4,5)P2 interaction has no effect on transferrin uptake. These results demonstrate the significance of the PH domain for dynamin function and suggest that its role may be to mediate interactions between dynamin and phosphoinositides.
Mol Cell Biol 1999 Feb
PMID:Essential role of the dynamin pleckstrin homology domain in receptor-mediated endocytosis. 989 Oct 74

The GTPase dynamin has been clearly implicated in clathrin-mediated endocytosis of synaptic vesicle membranes at the presynaptic nerve terminal. Here we describe a novel 52-kDa protein in rat brain that binds the proline-rich C terminus of dynamin. Syndapin I (synaptic, dynamin-associated protein I) is highly enriched in brain where it exists in a high molecular weight complex. Syndapin I can be involved in multiple protein-protein interactions via a src homology 3 (SH3) domain at the C terminus and two predicted coiled-coil stretches. Coprecipitation studies and blot overlay analyses revealed that syndapin I binds the brain-specific proteins dynamin I, synaptojanin, and synapsin I via an SH3 domain-specific interaction. Coimmunoprecipitation of dynamin I with antibodies recognizing syndapin I and colocalization of syndapin I with dynamin I at vesicular structures in primary neurons indicate that syndapin I associates with dynamin I in vivo and may play a role in synaptic vesicle endocytosis. Furthermore, syndapin I associates with the neural Wiskott-Aldrich syndrome protein, an actin-depolymerizing protein that regulates cytoskeletal rearrangement. These characteristics of syndapin I suggest a molecular link between cytoskeletal dynamics and synaptic vesicle recycling in the nerve terminal.
Mol Biol Cell 1999 Feb
PMID:Syndapin I, a synaptic dynamin-binding protein that associates with the neural Wiskott-Aldrich syndrome protein. 995 Jun 91

Quantitative analysis of Grb2/dynamin interaction through plasmon resonance analysis (BIAcore) using Grb2 mutants showed that the high affinity measured between Grb2 and dynamin is essentially mediated by the N-SH3 domain of Grb2. In order to study the interactions between Grb2 and either dynamin or Sos in more detail, Grb2 N-SH3 domains containing different mutations have been analysed. Two mutations were located on the hydrophobic platform binding proline-rich peptides (Y7V and P49L) and one (E40T) located in a region that we had previously shown to be essential for Grb2/dynamin interactions. Through NMR analysis, we have clearly demonstrated that the structure of the P49L mutant is not folded, while the other E40T and Y7V mutants adopt folded structures that are quite similar to that described for the reference domain. Nevertheless, these point mutations were shown to alter the overall stability of these domains by inducing an equilibrium between a folded and an unfolded form. The complex formed between the peptide VPPPVPPRRR, derived from Sos, and the E40T mutant was shown to have the same 3D structure as that described for the wild-type SH3 domain. However, the VPPPVPPRRR peptide adopts a slightly different orientation when it is complexed with the Y7V mutant. Finally, the affinity of the proline-rich peptide GPPPQVPSRPNR, derived from dynamin, for the Grb2 N-SH3 domain was too low to be analyzed by NMR. Thus, the interaction between either Sos or dynamin and the SH3 mutants were tested on a cellular homogenate by means of a far-Western blot analysis. In these conditions, the P49L mutant was shown to be devoid of affinity for Sos as well as for dynamin. The Y7V SH3 mutant displayed a decrease of affinity for both Sos and dynamin, while the E40T mutant exhibited a decrease of affinity only for dynamin. These results support the existence of two binding sites between dynamin and the Grb2 N-SH3 domain.
J Mol Biol 1999 Jul 16
PMID:Molecular and cellular analysis of Grb2 SH3 domain mutants: interaction with Sos and dynamin. 1039 25

Agonist-elicited receptor sequestration is strikingly different for the alpha(2A)- versus alpha(2B)-adrenergic receptor (alpha(2)-AR) subtypes; the alpha(2B)-AR undergoes rapid and extensive disappearance from the HEK 293 cell surface, whereas the alpha(2A)-AR does not (Daunt, D. A., Hurt, C., Hein, L., Kallio, J., Feng, F., and Kobilka, B. K. (1997) Mol. Pharmacol. 51, 711-720; Eason, M. G., and Liggett, S. B. (1992) J. Biol. Chem. 267, 25473-25479). Since recent reports suggest that endocytosis is required for some G protein-coupled receptors to stimulate the mitogen-activated protein (MAP) kinase cascade (Daaka, Y., Luttrell, L. M., Ahn, S., Della Rocca, G. J., Ferguson, S. S., Caron, M. G., and Lefkowitz, R. J. (1998) J. Biol. Chem. 273, 685-688; Luttrell, L. M., Daaka, Y., Della Rocca, G. J., and Lefkowitz, R. J. (1997) J. Biol. Chem. 272, 31648-31656; Ignatova, E. G., Belcheva, M. M., Bohn, L. M., Neuman, M. C., and Coscia, C. J. (1999) J. Neurosci. 19, 56-63), we evaluated the differential ability of these two subtypes to activate MAP kinase. We observed no correlation between subtype-dependent agonist-elicited receptor redistribution and receptor activation of the MAP kinase cascade. Furthermore, incubation of cells with K(+)-depleted medium eliminated alpha(2B)-AR internalization but did not eliminate MAP kinase activation, suggesting that receptor internalization is not a general prerequisite for activation of the MAP kinase cascade via G(i)-coupled receptors. We also noted that neither dominant negative dynamin (K44A) nor concanavalin A treatment dramatically altered MAP kinase activation or receptor redistribution, indicating that these experimental tools do not universally block G protein-coupled receptor internalization.
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PMID:Stimulation of mitogen-activated protein kinase by G protein-coupled alpha(2)-adrenergic receptors does not require agonist-elicited endocytosis. 1045 69

A number of behavioural and cellular studies have suggested that activity-dependent synaptic plasticity associated with learning and memory may lead to the expression of various genes whose protein products can play a critical role in memory acquisition and consolidation. Long-term potentiation (LTP) and long-term depression (LTD) represent two forms of synaptic plasticity which have been widely studied by electrophysiological techniques. However, the molecular mechanisms at target gene involved in the generation of long term depression remain to be determined. To elucidate the molecular mechanism underlying activity dependent synaptic remodeling in striatal long term depression, we used the mRNA differential display technology to isolate genes that are induced or modulated by high frequency stimulation of the corticostriatal pathway in a rat brain slice preparation. We have differentially displayed, by means of reverse transcriptase-polymerase chain reaction, mRNA species isolated from striatal slices in which long term depression was induced by tetanic stimuli as well as from slices stimulated at low frequency. We then compared radio-labeled RT-PCR banding patterns to isolate cDNAs that are differentially expressed. Three independent cDNAs were isolated and identified whose mRNA level were enhanced by tetanic stimulation inducing long term depression. We provide evidence that two of these genes encode proteins involved in synaptic vesicle trafficking (dynamin I and amphiphysin II). Moreover, expression of tissue plasminogen activator (t-PA) gene was also increased following striatal long term depression. Our data suggest that a complex pattern of genes acting at presynaptic level and extracellularly may be involved in LTD-associated synaptic remodeling.
Brain Res Mol Brain Res 1999 Sep 08
PMID:Modulation of gene expression following long-term synaptic depression in the striatum. 1052 2

The dynamin family of large GTPases has been implicated in vesicle formation from both the plasma membrane and various intracellular membrane compartments. The dynamin-like protein DLP1, recently identified in mammalian tissues, has been shown to be more closely related to the yeast dynamin proteins Vps1p and Dnm1p (42%) than to the mammalian dynamins (37%). Furthermore, DLP1 has been shown to associate with punctate vesicles that are in intimate contact with microtubules and the endoplasmic reticulum (ER) in mammalian cells. To define the function of DLP1, we have transiently expressed both wild-type and two mutant DLP1 proteins, tagged with green fluorescent protein, in cultured mammalian cells. Point mutations in the GTP-binding domain of DLP1 (K38A and D231N) dramatically changed its intracellular distribution from punctate vesicular structures to either an aggregated or a diffuse pattern. Strikingly, cells expressing DLP1 mutants or microinjected with DLP1 antibodies showed a marked reduction in ER fluorescence and a significant aggregation and tubulation of mitochondria by immunofluorescence microscopy. Consistent with these observations, electron microscopy of DLP1 mutant cells revealed a striking and quantitative change in the distribution and morphology of mitochondria and the ER. These data support very recent studies by other authors implicating DLP1 in the maintenance of mitochondrial morphology in both yeast and mammalian cells. Furthermore, this study provides the first evidence that a dynamin family member participates in the maintenance and distribution of the ER. How DLP1 might participate in the biogenesis of two presumably distinct organelle systems is discussed.
Mol Biol Cell 1999 Dec
PMID:The dynamin-like protein DLP1 is essential for normal distribution and morphology of the endoplasmic reticulum and mitochondria in mammalian cells. 1058 66

Little is known about the mechanism of mitochondrial division. We show here that mitochondria are disrupted by mutations in a C. elegans dynamin-related protein (DRP-1). Mutant DRP-1 causes the mitochondrial matrix to retract into large blebs that are both surrounded and connected by tubules of outer membrane. This indicates that scission of the mitochondrial outer membrane is inhibited, while scission of the inner membrane still occurs. Overexpressed wild-type DRP-1 causes mitochondria to become excessively fragmented, consistent with an active role in mitochondrial scission. DRP-1 fused to GFP is observed in spots on mitochondria where scission eventually occurs. These data indicate that wild-type DRP-1 contributes to the final stages of mitochondrial division by controlling scission of the mitochondrial outer membrane.
Mol Cell 1999 Nov
PMID:C. elegans dynamin-related protein DRP-1 controls severing of the mitochondrial outer membrane. 1061 28

It is well established that dynamin is involved in clathrin-dependent endocytosis, but relatively little is known about possible intracellular functions of this GTPase. Using confocal imaging, we found that endogenous dynamin was associated with the plasma membrane, the trans-Golgi network, and a perinuclear cluster of cation-independent mannose 6-phosphate receptor (CI-MPR)-containing structures. By electron microscopy (EM), it was shown that these structures were late endosomes and that the endogenous dynamin was preferentially localized to tubulo-vesicular appendices on these late endosomes. Upon induction of the dominant-negative dynK44A mutant, confocal microscopy demonstrated a redistribution of the CI-MPR in mutant-expressing cells. Quantitative EM analysis of the ratio of CI-MPR to lysosome-associated membrane protein-1 in endosome profiles revealed a higher colocalization of the two markers in dynK44A-expressing cells than in control cells. Western blot analysis showed that dynK44A-expressing cells had an increased cellular procathepsin D content. Finally, EM revealed that in dynK44A-expressing cells, endosomal tubules containing CI-MPR were formed. These results are in contrast to recent reports that dynamin-2 is exclusively associated with endocytic structures at the plasma membrane. They suggest instead that endogenous dynamin also plays an important role in the molecular machinery behind the recycling of the CI-MPR from endosomes to the trans-Golgi network, and we propose that dynamin is required for the final scission of vesicles budding from endosome tubules.
Mol Biol Cell 2000 Feb
PMID:Role for dynamin in late endosome dynamics and trafficking of the cation-independent mannose 6-phosphate receptor. 1067 8

MUC1 is a mucin-like type 1 transmembrane protein associated with the apical surface of epithelial cells. In human tumors of epithelial origin MUC1 is overexpressed in an underglycosylated form with truncated O-glycans and accumulates in intracellular compartments. To understand the basis for this altered subcellular localization, we compared the synthesis and trafficking of various glycosylated forms of MUC1 in normal (Chinese hamster ovary) cells and glycosylation-defective (ldlD) cells that lack the epimerase to make UDP-Gal/GalNAc from UDP-Glc/GlcNAc. Although the MUC1 synthesized in ldlD cells was rapidly degraded, addition of GalNAc alone to the culture media resulted in stabilization and near normal surface expression of MUC1 with truncated but sialylated O-glycans. Interestingly, the initial rate of endocytosis of this underglycosylated MUC1 was stimulated by twofold compared with fully glycosylated MUC1. However, the half-lives of the two forms were not different, indicating that trafficking to lysosomes was not affected. Both the normal and stimulated internalization of MUC1 could be blocked by hypertonic media, a hallmark of clathrin-mediated endocytosis. MUC1 endocytosis was also blocked by expression of a dominant-negative mutant of dynamin-1 (K44A), and MUC1 was observed in both clathrin-coated pits and vesicles by immunoelectron microscopy of ultrathin cryosections. Our data suggest that the subcellular redistribution of MUC1 in tumor cells could be a direct result of altered endocytic trafficking induced by its aberrant glycosylation; potential models are discussed. These results also implicate a new role for O-glycans on mucin-like membrane proteins entering the endocytic pathway through clathrin-coated pits.
Mol Biol Cell 2000 Mar
PMID:Clathrin-mediated endocytosis of MUC1 is modulated by its glycosylation state. 1071 2

Cytotoxic necrotizing factor 1 (CNF1), a protein produced by pathogenic strains of Escherichia coli, activates the p21 Rho-GTP-binding protein, inducing a profound reorganization of the actin cytoskeleton. CNF1 binds to its cell surface receptor on HEp-2 cells with high affinity (K(d) = 20 pM). In HEp-2 cells the action of CNF1 is not blocked in the presence of filipin, a drug described to reduce cholera toxin internalization by the caveolae-like mechanism. Moreover, HEp-2 cells, which express a dominant negative form of proteins that impair the formation of clathrin coated-vesicles and internalization of transferrin (Eps15, dynamin or intersectin-Src homology 3), are still sensitive to CNF1. In this respect, the endocytosis of CNF1 is similar to the plant toxin ricin. However, unlike ricin toxin, CNF1 does not cross the Golgi apparatus and requires an acidic cell compartment to transfer its enzymatic activity into the cytosol in a manner similar to that required by diphtheria toxin. As shown for diphtheria toxin, the pH-dependent membrane translocation step of CNF1 could be mimicked at the level of the plasma membrane by a brief exposure to a pH of </=5.2. CNF1 is the first bacterial toxin described that uses both a clathrin-independent endocytic mechanism and an acidic-dependent membrane translocation step in its delivery of the catalytic domain to the cell cytosol.
Mol Biol Cell 2000 May
PMID:The p21 Rho-activating toxin cytotoxic necrotizing factor 1 is endocytosed by a clathrin-independent mechanism and enters the cytosol by an acidic-dependent membrane translocation step. 1079 51


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