scholarly journals PI4P Promotes the Recruitment of the GGA Adaptor Proteins to the Trans-Golgi Network and Regulates Their Recognition of the Ubiquitin Sorting Signal

2007 ◽  
Vol 18 (7) ◽  
pp. 2646-2655 ◽  
Author(s):  
Jing Wang ◽  
Hui-Qiao Sun ◽  
Eric Macia ◽  
Tomas Kirchhausen ◽  
Hadiya Watson ◽  
...  
Keyword(s):  
Adaptor Proteins ◽  
Wild Type ◽  
Dual Roles ◽  
Sorting Signal ◽  
Trans Golgi Network ◽  
Clathrin Adaptor ◽  
Phosphatidylinositol 4 ◽  
Golgi Network

Phosphatidylinositol 4 phosphate (PI4P) is highly enriched in the trans-Golgi network (TGN). Here we establish that PI4P is a key regulator of the recruitment of the GGA clathrin adaptor proteins to the TGN and that PI4P has a novel role in promoting their recognition of the ubiquitin (Ub) sorting signal. Knockdown of PI4KIIα by RNA interference (RNAi), which depletes the TGN′s PI4P, impaired the recruitment of the GGAs to the TGN. GGAs bind PI4P primarily through their GAT domain, in a region called C-GAT, which also binds Ub but not Arf1. We identified two basic residues in the GAT domain that are essential for PI4P binding in vitro and for the recruitment of GGAs to the TGN in vivo. Unlike wild-type GGA, GGA with mutated GATs failed to rescue the abnormal TGN phenotype of the GGA RNAi-depleted cells. These residues partially overlap with those that bind Ub, and PI4P increased the affinity of the GAT domain for Ub. Because the recruitment of clathrin adaptors and their cargoes to the TGN is mediated through a web of low-affinity interactions, our results show that the dual roles of PI4P can promote specific GGA targeting and cargo recognition at the TGN.

scholarly journals Autoantigen Golgin-97, an Effector of Arl1 GTPase, Participates in Traffic from the Endosome to the Trans-Golgi Network

2004 ◽  
Vol 15 (10) ◽  
pp. 4426-4443 ◽  
Author(s):  
Lei Lu ◽  
Guihua Tai ◽  
Wanjin Hong
Keyword(s):  
Functional Study ◽  
Toxin B ◽  
Membrane Recruitment ◽  
Trans Golgi Network ◽  
Transport Assay ◽  
Retrograde Traffic ◽  
Golgi Network

The precise cellular function of Arl1 and its effectors, the GRIP domain Golgins, is not resolved, despite our recent understanding that Arl1 regulates the membrane recruitment of these Golgins. In this report, we describe our functional study of Golgin-97. Using a Shiga toxin B fragment (STxB)-based in vitro transport assay, we demonstrated that Golgin-97 plays a role in transport from the endosome to the trans-Golgi network (TGN). The recombinant GRIP domain of Golgin-97 as well as antibodies against Golgin-97 inhibited the transport of STxB in vitro. Membrane-associated Golgin-97, but not its cytosolic pool, was required in the in vitro transport assay. The kinetic characterization of inhibition by anti-Golgin-97 antibody in comparison with anti-Syntaxin 16 antibody established that Golgin-97 acts before Syntaxin 16 in endosome-to-TGN transport. Knock down of Golgin-97 or Arl1 by their respective small interference RNAs (siRNAs) also significantly inhibited the transport of STxB to the Golgi in vivo. In siRNA-treated cells with reduced levels of Arl1, internalized STxB was instead distributed peripherally. Microinjection of Golgin-97 antibody led to the fragmentation of Golgi apparatus and the arrested transport to the Golgi of internalized Cholera toxin B fragment. We suggest that Golgin-97 may function as a tethering molecule in endosome-to-TGN retrograde traffic.

scholarly journals A UDP-GlcNAc : βGal β1-6 GlcNAc transferase involved in bloodstream form N-glycan and procyclic form GPI anchor elaboration in Trypanosoma brucei.

2021 ◽  
Author(s):  
Samuel Martin Duncan ◽  
Rupa Nagar ◽  
Manuela Damerow ◽  
Dmitry V. Yashunsky ◽  
Benedetta Buzzi ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Bloodstream Form ◽  
Wild Type ◽  
Dual Roles ◽  
Gpi Anchor ◽  
Procyclic Form ◽  
Life Cycle Stages ◽  
Glcnac Transferase

Trypanosoma brucei has large carbohydrate extensions on its N-linked glycans and glycosylphosphatidylinositol (GPI) anchors in its bloodstream form (BSF) and procyclic form (PCF), respectively. The parasites glycoconjugate repertoire suggests at least 38 glycosyltransferase (GT) activities, 16 of which are unknown. Here, we probe the function(s) of a putative β3GT gene, TbGT10. The BSF null mutant is viable in vitro and in vivo and can differentiate into PCF, demonstrating non-essentiality. However, the absence of TbGT10 led to impaired elaboration of N-glycans and GPI anchor sidechains in BSF and PCF parasites, respectively. Glycosylation defects include reduced BSF glycoprotein binding to ricin and to monoclonal antibodies mAb139 and mAbCB1. The latter bind a carbohydrate epitope of lysosomal glycoprotein p67 that we show here, using synthetic glycans, consists of (-6Gal1-4GlcNAc1-)≥4 poly-N-acetyllactosamine repeats. Methylation linkage analysis of Pronase glycopeptides isolated from BSF wild-type and TbGT10 null parasites show a reduction in 6-O-substituted- and 3,6-di-O-substituted-Gal residues. Together, these data suggest that TbGT10 encodes a UDP-GlcNAc : βGal β1-6 GlcNAc-transferase active in both BSF and PCF life-cycle stages elaborating complex N-glycans and GPI sidechains, respectively. The β1-6 specificity of this β3GT gene product and its dual roles in N-glycan and GPI glycan elaboration are notable.

scholarly journals Yeast Gga Coat Proteins Function with Clathrin in Golgi to Endosome Transport

2001 ◽  
Vol 12 (6) ◽  
pp. 1885-1896 ◽  
Author(s):  
G. Costaguta ◽  
C. J. Stefan ◽  
E. S. Bensen ◽  
S. D. Emr ◽  
G. S. Payne
Keyword(s):  
Yeast Cells ◽  
Chain Gene ◽  
Temperature Sensitive ◽  
Coat Proteins ◽  
Trans Golgi Network ◽  
Clathrin Adaptor ◽  
Sensitive Allele ◽  
Golgi Network ◽  
In Cells

Gga proteins represent a newly recognized, evolutionarily conserved protein family with homology to the “ear” domain of the clathrin adaptor AP-1 γ subunit. Yeast cells contain two Gga proteins, Gga1p and Gga2p, that have been proposed to act in transport between thetrans-Golgi network and endosomes. Here we provide genetic and physical evidence that yeast Gga proteins function in trans-Golgi network clathrin coats. Deletion of Gga2p (gga2Δ), the major Gga protein, accentuates growth and α-factor maturation defects in cells carrying a temperature-sensitive allele of the clathrin heavy chain gene. Cells carrying eithergga2Δ or a deletion of the AP-1 β subunit gene(apl2Δ) alone are phenotypically normal, but cells carrying both gga2Δ andapl2Δ are defective in growth, α-factor maturation, and transport of carboxypeptidase S to the vacuole. Disruption of bothGGA genes and APL2 results in cells so severely compromised in growth that they form only microcolonies. Gga proteins can bind clathrin in vitro and cofractionate with clathrin-coated vesicles. Our results indicate that yeast Gga proteins play an important role in cargo-selective clathrin-mediated protein traffic from the trans-Golgi network to endosomes.

scholarly journals SMAP2, a Novel ARF GTPase-activating Protein, Interacts with Clathrin and Clathrin Assembly Protein and Functions on the AP-1–positive Early Endosome/Trans-Golgi Network

2006 ◽  
Vol 17 (6) ◽  
pp. 2592-2603 ◽  
Author(s):  
Waka Natsume ◽  
Kenji Tanabe ◽  
Shunsuke Kon ◽  
Naomi Yoshida ◽  
Toshio Watanabe ◽  
...  
Keyword(s):  
Brefeldin A ◽  
Adaptor Proteins ◽  
Early Endosome ◽  
Dependent Manner ◽  
Transferrin Receptors ◽  
Gtpase Activating Protein ◽  
Trans Golgi Network ◽  
Early Endosomes ◽  
Golgi Network

We recently reported that SMAP1, a GTPase-activating protein (GAP) for Arf6, directly interacts with clathrin and regulates the clathrin-dependent endocytosis of transferrin receptors from the plasma membrane. Here, we identified a SMAP1 homologue that we named SMAP2. Like SMAP1, SMAP2 exhibits GAP activity and interacts with clathrin heavy chain (CHC). Furthermore, we show that SMAP2 interacts with the clathrin assembly protein CALM. Unlike SMAP1, however, SMAP2 appears to be a regulator of Arf1 in vivo, because cells transfected with a GAP-negative SMAP2 mutant were resistant to brefeldin A. SMAP2 colocalized with the adaptor proteins for clathrin AP-1 and EpsinR on the early endosomes/trans-Golgi-network (TGN). Moreover, overexpression of SMAP2 delayed the accumulation of TGN38/46 molecule on the TGN. This suggests that SMAP2 functions in the retrograde, early endosome-to-TGN pathway in a clathrin- and AP-1–dependent manner. Thus, the SMAP gene family constitutes an important ArfGAP subfamily, with each SMAP member exerting both common and distinct functions in vesicle trafficking.

Interaction of amphiphysins with AP-1 clathrin adaptors at the membrane

2013 ◽  
Vol 450 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Sonja Huser ◽  
Gregor Suri ◽  
Pascal Crottet ◽  
Martin Spiess
Keyword(s):  
Plasma Membrane ◽  
Brefeldin A ◽  
Adaptor Protein ◽  
Trans Golgi Network ◽  
Src Homology 3 ◽  
Amphiphysin 1 ◽  
Src Homology ◽  
Golgi Network

The assembly of clathrin/AP (adaptor protein)-1-coated vesicles on the trans-Golgi network and endosomes is much less studied than that of clathrin/AP-2 vesicles at the plasma membrane for endocytosis. In vitro, the association of AP-1 with protein-free liposomes had been shown to require phosphoinositides, Arf1 (ADP-ribosylation factor 1)–GTP and additional cytosolic factor(s). We have purified an active fraction from brain cytosol and found it to contain amphiphysin 1 and 2 and endophilin A1, three proteins known to be involved in the formation of AP-2/clathrin coats at the plasma membrane. Assays with bacterially expressed and purified proteins showed that AP-1 stabilization on liposomes depends on amphiphysin 2 or the amphiphysin 1/2 heterodimer. Activity is independent of the SH3 (Src homology 3) domain, but requires interaction of the WDLW motif with γ-adaptin. Endogenous amphiphysin in neurons and transfected protein in cell lines co-localize perinuclearly with AP-1 at the trans-Golgi network. This localization depends on interaction of clathrin and the adaptor sequence in the amphiphysins and is sensitive to brefeldin A, which inhibits Arf1-dependent AP-1 recruitment. Interaction between AP-1 and amphiphysin 1/2 in vivo was demonstrated by co-immunoprecipitation after cross-linking. These results suggest an involvement of amphiphysins not only with AP-2 at the plasma membrane, but also in AP-1/clathrin coat formation at the trans-Golgi network.

scholarly journals Arabidopsis Disulfide Reductase, Trx-h2, Functions as an RNA Chaperone under Cold Stress

2021 ◽  
Vol 11 (15) ◽  
pp. 6865
Author(s):  
Eun Seon Lee ◽  
Joung Hun Park ◽  
Seong Dong Wi ◽  
Ho Byoung Chae ◽  
Seol Ki Paeng ◽  
...  
Keyword(s):  
Cold Stress ◽  
Wild Type ◽  
Rna Chaperone ◽  
E Coli ◽  
Cold Sensitive ◽  
Thioredoxin H ◽  
Functional Rnas

The thioredoxin-h (Trx-h) family of Arabidopsis thaliana comprises cytosolic disulfide reductases. However, the physiological function of Trx-h2, which contains an additional 19 amino acids at its N-terminus, remains unclear. In this study, we investigated the molecular function of Trx-h2 both in vitro and in vivo and found that Arabidopsis Trx-h2 overexpression (Trx-h2OE) lines showed significantly longer roots than wild-type plants under cold stress. Therefore, we further investigated the role of Trx-h2 under cold stress. Our results revealed that Trx-h2 functions as an RNA chaperone by melting misfolded and non-functional RNAs, and by facilitating their correct folding into active forms with native conformation. We showed that Trx-h2 binds to and efficiently melts nucleic acids (ssDNA, dsDNA, and RNA), and facilitates the export of mRNAs from the nucleus to the cytoplasm under cold stress. Moreover, overexpression of Trx-h2 increased the survival rate of the cold-sensitive E. coli BX04 cells under low temperature. Thus, our data show that Trx-h2 performs function as an RNA chaperone under cold stress, thus increasing plant cold tolerance.

scholarly journals Neuroprotective Potential of a Small Molecule RET Agonist in Cultured Dopamine Neurons and Hemiparkinsonian Rats

2021 ◽  
pp. 1-24
Author(s):  
Juho-Matti Renko ◽  
Arun Kumar Mahato ◽  
Tanel Visnapuu ◽  
Konsta Valkonen ◽  
Mati Karelson ◽  
...  
Keyword(s):  
Mapk Signaling ◽  
Dopamine Neurons ◽  
Dopamine Depletion ◽  
Wild Type ◽  
Disease Modifying Therapy ◽  
Immortalized Cells ◽  
Midbrain Dopamine ◽  
6 Hydroxydopamine

Background: Parkinson’s disease (PD) is a progressive neurological disorder where loss of dopamine neurons in the substantia nigra and dopamine depletion in the striatum cause characteristic motor symptoms. Currently, no treatment is able to halt the progression of PD. Glial cell line-derived neurotrophic factor (GDNF) rescues degenerating dopamine neurons both in vitro and in animal models of PD. When tested in PD patients, however, the outcomes from intracranial GDNF infusion paradigms have been inconclusive, mainly due to poor pharmacokinetic properties. Objective: We have developed drug-like small molecules, named BT compounds that activate signaling through GDNF’s receptor, the transmembrane receptor tyrosine kinase RET, both in vitro and in vivo and are able to penetrate through the blood-brain barrier. Here we evaluated the properties of BT44, a second generation RET agonist, in immortalized cells, dopamine neurons and rat 6-hydroxydopamine model of PD. Methods: We used biochemical, immunohistochemical and behavioral methods to evaluate the effects of BT44 on dopamine system in vitro and in vivo. Results: BT44 selectively activated RET and intracellular pro-survival AKT and MAPK signaling pathways in immortalized cells. In primary midbrain dopamine neurons cultured in serum-deprived conditions, BT44 promoted the survival of the neurons derived from wild-type, but not from RET knockout mice. BT44 also protected cultured wild-type dopamine neurons from MPP +-induced toxicity. In a rat 6-hydroxydopamine model of PD, BT44 reduced motor imbalance and could have protected dopaminergic fibers in the striatum. Conclusion: BT44 holds potential for further development into a novel, possibly disease-modifying therapy for PD.

scholarly journals The double-stranded DNA-binding proteins TEBP-1 and TEBP-2 form a telomeric complex with POT-1

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sabrina Dietz ◽  
Miguel Vasconcelos Almeida ◽  
Emily Nischwitz ◽  
Jan Schreier ◽  
Nikenza Viceconte ◽  
...  
Keyword(s):  
Quantitative Proteomics ◽  
Wild Type ◽  
C Elegans ◽  
Double Stranded Dna ◽  
Telomere Sequence ◽  
Proteomics Approach ◽  
Telomeric Protein ◽  
Regulate Telomere Length

AbstractTelomeres are bound by dedicated proteins, which protect them from DNA damage and regulate telomere length homeostasis. In the nematode Caenorhabditis elegans, a comprehensive understanding of the proteins interacting with the telomere sequence is lacking. Here, we harnessed a quantitative proteomics approach to identify TEBP-1 and TEBP-2, two paralogs expressed in the germline and embryogenesis that associate to telomeres in vitro and in vivo. tebp-1 and tebp-2 mutants display strikingly distinct phenotypes: tebp-1 mutants have longer telomeres than wild-type animals, while tebp-2 mutants display shorter telomeres and a Mortal Germline. Notably, tebp-1;tebp-2 double mutant animals have synthetic sterility, with germlines showing signs of severe mitotic and meiotic arrest. Furthermore, we show that POT-1 forms a telomeric complex with TEBP-1 and TEBP-2, which bridges TEBP-1/-2 with POT-2/MRT-1. These results provide insights into the composition and organization of a telomeric protein complex in C. elegans.

scholarly journals Brown Spiders’ Phospholipases-D with Potential Therapeutic Applications: Functional Assessment of Mutant Isoforms

Biomedicines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 320
Author(s):  
Thaís Pereira da Silva ◽  
Fernando Jacomini de Castro ◽  
Larissa Vuitika ◽  
Nayanne Louise Costacurta Polli ◽  
Bruno César Antunes ◽  
...  
Keyword(s):  
Structural Changes ◽  
Capillary Permeability ◽  
Structural Data ◽  
Histopathological Analysis ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Antigenic Properties ◽  
Harmful Effects

Phospholipases-D (PLDs) found in Loxosceles spiders’ venoms are responsible for the dermonecrosis triggered by envenomation. PLDs can also induce other local and systemic effects, such as massive inflammatory response, edema, and hemolysis. Recombinant PLDs reproduce all of the deleterious effects induced by Loxosceles whole venoms. Herein, wild type and mutant PLDs of two species involved in accidents—L. gaucho and L. laeta—were recombinantly expressed and characterized. The mutations are related to amino acid residues relevant for catalysis (H12-H47), magnesium ion coordination (E32-D34) and binding to phospholipid substrates (Y228 and Y228-Y229-W230). Circular dichroism and structural data demonstrated that the mutant isoforms did not undergo significant structural changes. Immunoassays showed that mutant PLDs exhibit conserved epitopes and kept their antigenic properties despite the mutations. Both in vitro (sphingomyelinase activity and hemolysis) and in vivo (capillary permeability, dermonecrotic activity, and histopathological analysis) assays showed that the PLDs with mutations H12-H47, E32-D34, and Y228-Y229-W230 displayed only residual activities. Results indicate that these mutant toxins are suitable for use as antigens to obtain neutralizing antisera with enhanced properties since they will be based on the most deleterious toxins in the venom and without causing severe harmful effects to the animals in which these sera are produced.

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