The Experts below are selected from a list of 1731 Experts worldwide ranked by ideXlab platform
Klaus T. Wanner - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with tricyclic cage structures in the lipophilic domain as GABA uptake inhibitors
Medicinal Chemistry Research, 2020Co-Authors: Heinrich-karl A. Rudy, Georg Höfner, Klaus T. WannerAbstract:A new class of GABA reuptake inhibitors with sterically demanding, highly rigid tricyclic cage structures as the lipophilic domain was synthesized and investigated in regard to their biological activity at the murine GABA transporters (mGAT1–mGAT4). The construction of these compounds, consisting of nipecotic acid, a symmetric tricyclic amine, and a plain hydrocarbon linker connecting the two subunits via their amino nitrogens, was accomplished via reductive amination of a nipecotic acid derivative with an N -alkyl substituent displaying a terminal aldehyde function with tricyclic secondary amines. The target compounds varied with regard to spacer length, the bridge size of one of the bridges, and the substituents of the tricyclic skeleton to study the impact of these changes on their potency. Among the tested compounds nipecotic acid ethyl ester derivates with phenyl residues attached to the cage subunit showed reasonable inhibitory potency and subtype selectivity in favor of MGAT3 and mGAT4, respectively.
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Synthesis and biological evaluation of α- and β-hydroxy substituted amino acid derivatives as potential mGAT1–4 inhibitors
Medicinal Chemistry Research, 2020Co-Authors: Janina C. Andreß, Georg Höfner, Michael C. Böck, Klaus T. WannerAbstract:In this study, we report the synthesis and biological evaluation of a variety of α- and β-hydroxy substituted amino acid derivatives as potential amino acid subunits in inhibitors of GABA uptake transporters (GATs). In order to ensure that the test compounds adopt a binding pose similar to that presumed for related larger GAT inhibitors, lipophilic residues were introduced either at the amino nitrogen atom or at the alcohol function. Several of the synthesized compounds were found to exhibit similar inhibitory activity at the GAT subtypes mGAT2, MGAT3, and mGAT4, respectively, as compared with the reference N-butylnipecotic acid. Hence, these compounds might serve as starting point for future developments of more complex GAT inhibitors.
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Synthesis and biological evaluation of fluorescent GAT-ligands based on asymmetric substituted BODIPY dyes
Medicinal Chemistry Research, 2020Co-Authors: Markus Daerr, Lars Allmendinger, Georg Höfner, Klaus T. WannerAbstract:The present study aimed at the development of fluorescent inhibitors addressing the GABA transporters mGAT1–mGAT4 as potential tool compounds in fluorescence based biological assays. The design of these fluorescent GAT inhibitors followed the structural motifs common for many GAT1–GAT4 inhibitors publicly known except that the lipophilic domain present in this compounds was replaced by a BODIPY moiety to serve as a fluorescent subunit. The fluorescent compounds obtained that way were tested for their inhibitory potencies and subtype selectivities at the four murine GABA transporter subtypes mGAT1–mGAT4 and for their binding affinity for mGAT1. All BODIPY derivatives displayed only low inhibitory potencies and subtype selectivities at the GABA transport proteins mGAT1–mGAT4, as well as low affinities for mGAT1. Still, compounds were found with reasonable binding affinities towards mGAT1 (p K _i ~ 5.0) and inhibitory potencies at mGAT2 and mGAT4 (pIC_50 ~ 5.0).
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Synthesis and biological evaluation of fluorescent GAT-ligands based on meso-substituted BODIPY dyes
Medicinal Chemistry Research, 2020Co-Authors: Markus Daerr, Georg Höfner, Jorg Pabel, Peter Mayer, Klaus T. WannerAbstract:BODIPY dyes are well known for their outstanding spectroscopic properties and are therefore established in a range of fluorescence based analysis techniques for in vitro as well as for in vivo measurements. For the first time, we designed and synthesized a series of fluorescent ligands for the SLC6 family transporters mGAT1–mGAT4 based on BODIPY dyes as fluorogenic subunits. In the novel series of fluorescent compounds, BODIPY dye subunits are linked with an alkyl chain of three to five carbon atoms that originates from the meso -position of the BODIPY dye to the amino function of different cyclic amines. Screening of these fluorescent probes for their biological activity as GABA uptake inhibitors of mGAT1–mGAT4 revealed ligands with pIC_50 values up to 5.35.
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Synthesis and biological evaluation of a series of N-alkylated imidazole alkanoic acids as MGAT3 selective GABA uptake inhibitors
European journal of medicinal chemistry, 2016Co-Authors: Silke Kerscher-hack, Georg Höfner, Thejavathi Renukappa-gutke, Klaus T. WannerAbstract:In this paper, we report the synthesis and biological evaluation of a series of 1,5- and 1,4- substituted derivatives of 1H-imidazol-4-ylacetic acid, a series of 1,2-substituted 3-(1H-imidazol-2-yl)propanoic acid and an N-substituted (2E)-3-(1H-imidazol-2-yl)prop-2-enoic acid as new MGAT3 inhibitors. The lipophilic moieties attached to the N-atom of the parent structures were delineated from the 2-[9-(4-methoxyphenyl)-9H-fluoren-9-yl]oxyethyl residue, known from a prototypic MGAT3 inhibitor. For the structure-activity-relationship studies, the spacer between the N-atom of the imidazole ring and the 2-[9-(4-methoxyphenyl)-9H-fluoren-9-yl] moiety was varied in length from three to six atoms, and in nature being either a pure saturated or unsaturated alkyl chain or an alkyl chain containing up to two ether functions. The compounds were characterized for inhibitory potencies at mouse GABA transporter proteins mGAT1-mGAT4. Among the 1,2-substituted compounds, the N-alkylated (2E)-3-(1H-imidazol-2-yl)prop-2-enoic acid 12e containing a C5O spacer exhibits a pIC50 value of 5.13 ± 0.04 at MGAT3, but is devoid of significant selectivity for this GABA transporter. However, the inhibitory potency displayed by 12e at MGAT3 nominally surpasses that of SNAP-5294 reported as the most potent inhibitor of MGAT3 so far.
Georg Höfner - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with tricyclic cage structures in the lipophilic domain as GABA uptake inhibitors
Medicinal Chemistry Research, 2020Co-Authors: Heinrich-karl A. Rudy, Georg Höfner, Klaus T. WannerAbstract:A new class of GABA reuptake inhibitors with sterically demanding, highly rigid tricyclic cage structures as the lipophilic domain was synthesized and investigated in regard to their biological activity at the murine GABA transporters (mGAT1–mGAT4). The construction of these compounds, consisting of nipecotic acid, a symmetric tricyclic amine, and a plain hydrocarbon linker connecting the two subunits via their amino nitrogens, was accomplished via reductive amination of a nipecotic acid derivative with an N -alkyl substituent displaying a terminal aldehyde function with tricyclic secondary amines. The target compounds varied with regard to spacer length, the bridge size of one of the bridges, and the substituents of the tricyclic skeleton to study the impact of these changes on their potency. Among the tested compounds nipecotic acid ethyl ester derivates with phenyl residues attached to the cage subunit showed reasonable inhibitory potency and subtype selectivity in favor of MGAT3 and mGAT4, respectively.
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Synthesis and biological evaluation of α- and β-hydroxy substituted amino acid derivatives as potential mGAT1–4 inhibitors
Medicinal Chemistry Research, 2020Co-Authors: Janina C. Andreß, Georg Höfner, Michael C. Böck, Klaus T. WannerAbstract:In this study, we report the synthesis and biological evaluation of a variety of α- and β-hydroxy substituted amino acid derivatives as potential amino acid subunits in inhibitors of GABA uptake transporters (GATs). In order to ensure that the test compounds adopt a binding pose similar to that presumed for related larger GAT inhibitors, lipophilic residues were introduced either at the amino nitrogen atom or at the alcohol function. Several of the synthesized compounds were found to exhibit similar inhibitory activity at the GAT subtypes mGAT2, MGAT3, and mGAT4, respectively, as compared with the reference N-butylnipecotic acid. Hence, these compounds might serve as starting point for future developments of more complex GAT inhibitors.
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Synthesis and biological evaluation of fluorescent GAT-ligands based on asymmetric substituted BODIPY dyes
Medicinal Chemistry Research, 2020Co-Authors: Markus Daerr, Lars Allmendinger, Georg Höfner, Klaus T. WannerAbstract:The present study aimed at the development of fluorescent inhibitors addressing the GABA transporters mGAT1–mGAT4 as potential tool compounds in fluorescence based biological assays. The design of these fluorescent GAT inhibitors followed the structural motifs common for many GAT1–GAT4 inhibitors publicly known except that the lipophilic domain present in this compounds was replaced by a BODIPY moiety to serve as a fluorescent subunit. The fluorescent compounds obtained that way were tested for their inhibitory potencies and subtype selectivities at the four murine GABA transporter subtypes mGAT1–mGAT4 and for their binding affinity for mGAT1. All BODIPY derivatives displayed only low inhibitory potencies and subtype selectivities at the GABA transport proteins mGAT1–mGAT4, as well as low affinities for mGAT1. Still, compounds were found with reasonable binding affinities towards mGAT1 (p K _i ~ 5.0) and inhibitory potencies at mGAT2 and mGAT4 (pIC_50 ~ 5.0).
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novel mouse gaba uptake inhibitors with enhanced inhibitory activity toward MGAT3 4 and their effect on pain threshold in mice
European Journal of Medicinal Chemistry, 2020Co-Authors: Paula Zareba, Georg Höfner, Katarzyna Malawska, Alicja Nowaczyk, Anna Rapacz, Adrian Podkowa, Beata Gryzlo, Kinga Salat, łukasz Fijalkowski, Anna FurgalaAbstract:Abstract γ-Aminobutyric acid (GABA) uptake transporters are membrane transport proteins that are involved in the pathophysiology of a number of neurological disorders. Some types of chronic pain appear to result from the dysfunction of the GABAergic system. The deficiency of mouse GAT1 transporter (mGAT1) abolishes the nociceptive response, which means that mGAT1 inhibition is an appropriate medical approach to achieve analgesia. The mGAT4 transporter is the second most abundant GAT subtype in the brain; however, its physiological role has not yet been fully understood in the central nervous system. In this study, we examined whether the combination of mGAT1 and MGAT3/mGAT4 inhibition in a single molecule might lead to potentially synergistic effects improving analgesic activity to relieve neuropathic pain. To study this hypothesis, new GABA uptake inhibitors were designed, synthesized, and evaluated in terms of their activity and subtype selectivity for mGAT1-4. Among new functionalized amino acid derivatives of serine and GABA analogs, compounds with preferential MGAT3/4 inhibitory activity were discovered. Two selected hits (19b and 31c) were subjected to in vivo tests. We found a statistically significant antiallodynic activity in the von Frey test in diabetic and oxaliplatin-induced neuropathic pain model. The novel compounds (4-hydroxybutanoic, 4-hydroxypentanoic, and 4-aminobutanoic acid derivatives and serine analogs) provide new insights into the structure–activity relationship of MGAT3/mGAT4 inhibitors and indicate a new direction in the search for potential treatment of neuropathic pain of various origin.
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Synthesis and biological evaluation of fluorescent GAT-ligands based on meso-substituted BODIPY dyes
Medicinal Chemistry Research, 2020Co-Authors: Markus Daerr, Georg Höfner, Jorg Pabel, Peter Mayer, Klaus T. WannerAbstract:BODIPY dyes are well known for their outstanding spectroscopic properties and are therefore established in a range of fluorescence based analysis techniques for in vitro as well as for in vivo measurements. For the first time, we designed and synthesized a series of fluorescent ligands for the SLC6 family transporters mGAT1–mGAT4 based on BODIPY dyes as fluorogenic subunits. In the novel series of fluorescent compounds, BODIPY dye subunits are linked with an alkyl chain of three to five carbon atoms that originates from the meso -position of the BODIPY dye to the amino function of different cyclic amines. Screening of these fluorescent probes for their biological activity as GABA uptake inhibitors of mGAT1–mGAT4 revealed ligands with pIC_50 values up to 5.35.
Pamela Stanley - One of the best experts on this subject based on the ideXlab platform.
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MGAT1 and Complex N-Glycans Regulate ERK Signaling During Spermatogenesis
Nature Publishing Group, 2018Co-Authors: Barnali Biswas, Subha Sundaram, Frank Batista, Pamela StanleyAbstract:Abstract Mechanisms that regulate spermatogenesis in mice are important to define as they often apply to fertility in man. We previously showed that conditional deletion of the mouse Mgat1 gene (Mgat1 cKO) in spermatogonia causes a germ-cell autonomous defect leading to infertility. MGAT1 is the N-acetylglucosaminyltransferase (GlcNAcT-I) that initiates the synthesis of complex N-glycans. Mechanistic bases of MGAT1 loss were investigated in germ cells from 22- and 23-day males, before any changes in germ cell morphology were apparent. Gene expression changes induced by deletion of Mgat1 were determined using the Affymetrix gene chip Mouse Mogene 2.0 ST array, and relationships were investigated by bioinformatics including Gene Ontology (GO), Ingenuity Pathway Analysis (IPA), and Gene Set Enrichment Analysis (GSEA). The loss of complex N-glycans promoted the premature up-regulation of genes normally expressed later in spermatogenesis and spermiogenesis, and IPA and GSEA implicated ERK signaling. EGFR and PDGFRA transcripts and ERK1/2 signaling were reduced in 22-day Mgat1 cKO germ cells. Basigin, a germ cell target of MGAT1, activated ERK1/2 in CHO cells, but not in a Lec1 CHO mutant that lacks MGAT1 and complex N-glycans. Thus, MGAT1 is required to regulate ERK1/2 signaling during spermatogenesis, potentially via different mechanisms
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GnT1IP-L specifically inhibits MGAT1 in the Golgi via its luminal domain
eLife, 2015Co-Authors: Hung Hsiang Huang, Antti Hassinen, Sakari Kellokumpu, Subha Sundaram, Andrej Nikolai Spiess, Pamela StanleyAbstract:Mouse GnT1IP-L, and membrane-bound GnT1IP-S (MGAT4D) expressed in cultured cells inhibit MGAT1, the N-acetylglucosaminyltransferase that initiates the synthesis of hybrid and complex N-glycans. However, it is not known where in the secretory pathway GnT1IP-L inhibits MGAT1, nor whether GnT1IP-L inhibits other N-glycan branching N-acetylglucosaminyltransferases of the medial Golgi. We show here that the luminal domain of GnT1IP-L contains its inhibitory activity. Retention of GnT1IP-L in the endoplasmic reticulum (ER) via the N-terminal region of human invariant chain p33, with or without C-terminal KDEL, markedly reduced inhibitory activity. Dynamic fluorescent resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) assays revealed homomeric interactions for GnT1IP-L in the ER, and heteromeric interactions with MGAT1 in the Golgi. GnT1IP-L did not generate a FRET signal with MGAT2, MGAT3, MGAT4B or MGAT5 medial Golgi GlcNAc-tranferases. GnT1IP/Mgat4d transcripts are expressed predominantly in spermatocytes and spermatids in mouse, and are reduced in men with impaired spermatogenesis.
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Bisected, complex N-glycans and galectins in mouse mammary tumor progression and human breast cancer
Glycobiology, 2013Co-Authors: Hazuki E. Miwa, Wade Koba, Eugene J. Fine, Orsolya Giricz, Paraic A. Kenny, Pamela StanleyAbstract:Bisected, complex N-glycans on glycoproteins are generated by the glycosyltransferase MGAT3 and cause reduced cell surface binding of galectins. Previously, we showed that MGAT3 reduces growth factor signaling and retards mammary tumor progression driven by the Polyoma middle T antigen (PyMT) expressed in mammary epithelium under the mouse mammary tumor virus (MMTV) promoter. However, the penetrance of the tumor phenotype became variable in mixed FVB/N and C57BL/6 female mice and we therefore investigated a congenic C57BL/6 MGAT3−/−/MMTV-PyMT model. In the absence of MGAT3, C57BL/6 MGAT3−/−/MMTV-PyMT females exhibited accelerated tumor appearance and increased tumor burden, glucose uptake in tumors and lung metastasis. Nevertheless, activation of extracellular signal-regulated kinase (ERK)1/2 or protein kinase B (AKT) was reduced in ∼20-week C57BL/6 MMTV-PyMT tumors lacking MGAT3. Activation of focal adhesion kinase (FAK), protein tyrosine kinase Src, and p38 mitogen-activated protein kinase were similar to that of controls. All the eight mouse galectin genes were expressed in mammary tumors and tumor epithelial cells (TECs), but galectin-2 and -12 were not detected by western analysis in tumors, and galectin-7 was not detected in 60% of the TEC lines. From microarray data reported for human breast cancers, at least 10 galectin and 7 N-glycan N-acetylglucosaminyl (GlcNAc)-transferase (MGAT) genes are expressed in tumor tissue, and expression often varies significantly between different breast cancer subtypes. Thus, in summary, while MGAT3 and bisected complex N-glycans retard mouse mammary tumor progression, genetic background may modify this effect; identification of key galectins that promote mammary tumor progression in mice is not straightforward because all the eight galectin genes are expressed; and high levels of MGAT3, galectin-4, -8, -10, -13 and -14 transcripts correlate with better relapse-free survival in human breast cancer.
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The Bisecting GlcNAc on N-Glycans Inhibits Growth Factor Signaling and Retards Mammary Tumor Progression
Cancer research, 2010Co-Authors: Yinghui Song, Jason A. Aglipay, Joshua D. Bernstein, Sumanta Goswami, Pamela StanleyAbstract:The branching of complex N-glycans attached to growth factor receptors promotes tumor progression by prolonging growth factor signaling. The addition of the bisecting GlcNAc to complex N-glycans by MGAT3 has varying effects on cell adhesion, cell migration, and hepatoma formation. Here, we show that Chinese hamster ovary cells expressing MGAT3 and the polyoma middle T (PyMT) antigen have reduced cell proliferation and growth factor signaling dependent on a galectin lattice. The MGAT3 gene is not expressed in virgin mammary gland but is upregulated during lactation and is expressed in mouse mammary tumor virus (MMTV)/PyMT tumors. Mice lacking MGAT3 that cannot transfer the bisecting GlcNAc to N-glycans acquire PyMT-induced mammary tumors more rapidly and have an increased tumor burden, increased migration of tumor cells, and increased early metastasis to lung. Tumors and tumor-derived cells lacking MGAT3 exhibit enhanced signaling through the Ras pathway and reduced amounts of functionally glycosylated α-dystroglycan. Constitutive overexpression of an MMTV/MGAT3 transgene inhibits early mammary tumor development and tumor cell migration. Thus, the addition of the bisecting GlcNAc to complex N-glycans of mammary tumor cell glycoprotein receptors is a cell autonomous mechanism serving to retard tumor progression by reducing growth factor signaling. Cancer Res; 70(8); 3361–71. ©2010 AACR.
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Molecular analysis of three gain-of-function CHO mutants that add the bisecting GlcNAc to N-glycans.
Glycobiology, 2004Co-Authors: Pamela Stanley, Subha Sundaram, Jian Tang, Shaolin ShiAbstract:LEC10 Chinese hamster ovary (CHO) cells are gain-of-function mutants that express N-acetylglucosaminyltransferase III (GlcNAc-TIII), the glycosyltransferase that adds the bisecting GlcNAc to complex N-glycans. LEC10 cells are useful for glycosylation engineering of recombinant glycoproteins, including antibody therapeutics, for defining lectin recognition specificities and for determining biological functions of the bisecting GlcNAc. We show that three CHO mutants, LEC10, LEC10A, and LEC10B, arose due to transcriptional activation of the quiescent CHO MGAT3 gene. They each express MGAT3 gene transcripts of approximately 4.7 kb at different levels (LEC10B > LEC10 > LEC10A). Southern analyses gave a single band in LEC10, LEC10A, and parent CHO DNA with four restriction enzymes but an additional band with three of them in LEC10B genomic DNA, indicative of a duplication event in LEC10B. The deduced amino acid sequence of the MGAT3 gene expressed in each CHO mutant and in parent CHO genomic DNA is identical. However, 5' UTR sequences differ with LEC10 and LEC10B containing a 5' UTR segment of the Atf4 gene downstream of the MGAT3 gene in human and mouse. Somatic cell hybrid analysis indicated that the LEC10B MGAT3 gene was induced by a cis mechanism. LEC10B glycoproteins bound more erythroagglutinin lectin (E-PHA) than LEC10 glycoproteins and MALDI-TOF MS revealed a broad spectrum of complex, bisected N-glycans expressed by the LEC10B mutant. LEC10B is therefore the cell line of choice for producing recombinant glycoproteins carrying bisected N-glycans and for investigating biological functions of the bisecting GlcNAc.
Sakari Kellokumpu - One of the best experts on this subject based on the ideXlab platform.
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N-acetylglucosaminyltransferases and nucleotide sugar transporters form multi-enzyme–multi-transporter assemblies in golgi membranes in vivo
Cellular and Molecular Life Sciences, 2019Co-Authors: Fawzi Khoder-agha, Paulina Sosicka, Antti Hassinen, Tuomo Glumoff, Mariusz Olczak, Maria Escriva Conde, Sakari KellokumpuAbstract:Branching and processing of N -glycans in the medial-Golgi rely both on the transport of the donor UDP- N -acetylglucosamine (UDP-GlcNAc) to the Golgi lumen by the SLC35A3 nucleotide sugar transporter (NST) as well as on the addition of the GlcNAc residue to terminal mannoses in nascent N -glycans by several linkage-specific N -acetyl-glucosaminyltransferases (MGAT1-MGAT5). Previous data indicate that the MGATs and NSTs both form higher order assemblies in the Golgi membranes. Here, we investigate their specific and mutual interactions using high-throughput FRET- and BiFC-based interaction screens. We show that MGAT1, MGAT2, MGAT3, MGAT4B (but not MGAT5) and Golgi alpha-mannosidase IIX (MAN2A2) form several distinct molecular assemblies with each other and that the MAN2A2 acts as a central hub for the interactions. Similar assemblies were also detected between the NSTs SLC35A2, SLC35A3, and SLC35A4. Using in vivo BiFC-based FRET interaction screens, we also identified novel ternary complexes between the MGATs themselves or between the MGATs and the NSTs. These findings suggest that the MGATs and the NSTs self-assemble into multi-enzyme/multi-transporter complexes in the Golgi membranes in vivo to facilitate efficient synthesis of complex N -glycans.
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n acetylglucosaminyltransferases and nucleotide sugar transporters form multi enzyme multi transporter assemblies in golgi membranes in vivo
Cellular and Molecular Life Sciences, 2019Co-Authors: Fawzi Khoderagha, Paulina Sosicka, Maria Escriva Conde, Antti Hassinen, Tuomo Glumoff, Mariusz Olczak, Sakari KellokumpuAbstract:Branching and processing of N-glycans in the medial-Golgi rely both on the transport of the donor UDP-N-acetylglucosamine (UDP-GlcNAc) to the Golgi lumen by the SLC35A3 nucleotide sugar transporter (NST) as well as on the addition of the GlcNAc residue to terminal mannoses in nascent N-glycans by several linkage-specific N-acetyl-glucosaminyltransferases (MGAT1-MGAT5). Previous data indicate that the MGATs and NSTs both form higher order assemblies in the Golgi membranes. Here, we investigate their specific and mutual interactions using high-throughput FRET- and BiFC-based interaction screens. We show that MGAT1, MGAT2, MGAT3, MGAT4B (but not MGAT5) and Golgi alpha-mannosidase IIX (MAN2A2) form several distinct molecular assemblies with each other and that the MAN2A2 acts as a central hub for the interactions. Similar assemblies were also detected between the NSTs SLC35A2, SLC35A3, and SLC35A4. Using in vivo BiFC-based FRET interaction screens, we also identified novel ternary complexes between the MGATs themselves or between the MGATs and the NSTs. These findings suggest that the MGATs and the NSTs self-assemble into multi-enzyme/multi-transporter complexes in the Golgi membranes in vivo to facilitate efficient synthesis of complex N-glycans.
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GnT1IP-L specifically inhibits MGAT1 in the Golgi via its luminal domain
eLife, 2015Co-Authors: Hung Hsiang Huang, Antti Hassinen, Sakari Kellokumpu, Subha Sundaram, Andrej Nikolai Spiess, Pamela StanleyAbstract:Mouse GnT1IP-L, and membrane-bound GnT1IP-S (MGAT4D) expressed in cultured cells inhibit MGAT1, the N-acetylglucosaminyltransferase that initiates the synthesis of hybrid and complex N-glycans. However, it is not known where in the secretory pathway GnT1IP-L inhibits MGAT1, nor whether GnT1IP-L inhibits other N-glycan branching N-acetylglucosaminyltransferases of the medial Golgi. We show here that the luminal domain of GnT1IP-L contains its inhibitory activity. Retention of GnT1IP-L in the endoplasmic reticulum (ER) via the N-terminal region of human invariant chain p33, with or without C-terminal KDEL, markedly reduced inhibitory activity. Dynamic fluorescent resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) assays revealed homomeric interactions for GnT1IP-L in the ER, and heteromeric interactions with MGAT1 in the Golgi. GnT1IP-L did not generate a FRET signal with MGAT2, MGAT3, MGAT4B or MGAT5 medial Golgi GlcNAc-tranferases. GnT1IP/Mgat4d transcripts are expressed predominantly in spermatocytes and spermatids in mouse, and are reduced in men with impaired spermatogenesis.
Jorg Pabel - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and biological evaluation of fluorescent GAT-ligands based on meso-substituted BODIPY dyes
Medicinal Chemistry Research, 2020Co-Authors: Markus Daerr, Georg Höfner, Jorg Pabel, Peter Mayer, Klaus T. WannerAbstract:BODIPY dyes are well known for their outstanding spectroscopic properties and are therefore established in a range of fluorescence based analysis techniques for in vitro as well as for in vivo measurements. For the first time, we designed and synthesized a series of fluorescent ligands for the SLC6 family transporters mGAT1–mGAT4 based on BODIPY dyes as fluorogenic subunits. In the novel series of fluorescent compounds, BODIPY dye subunits are linked with an alkyl chain of three to five carbon atoms that originates from the meso -position of the BODIPY dye to the amino function of different cyclic amines. Screening of these fluorescent probes for their biological activity as GABA uptake inhibitors of mGAT1–mGAT4 revealed ligands with pIC_50 values up to 5.35.
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development of an s 1 2 tris 4 methoxyphenyl methoxy ethyl piperidine 3 carboxylic acid s snap 5114 carba analogue inhibitor for murine γ aminobutyric acid transporter type 4
ChemMedChem, 2012Co-Authors: Jorg Pabel, Lars Allmendinger, Georg Höfner, Mark Faust, Cornelia Prehn, Babette Worlein, Klaus T. WannerAbstract:: A series of GABA uptake inhibitors related to (S)-1-{2-[tris(4-methoxyphenyl)methoxy]ethyl}piperidine-3-carboxylic acid [(S)-SNAP-5114], the most potent mGAT4 inhibitor known so far, were synthesized and biologically evaluated for their inhibitory potency at the four GABA uptake transporters mGAT1-4 stably expressed in HEK-293 cell lines. New analogues were developed with potencies that are similar to or slightly higher than those of current mGAT4 inhibitors, but with distinctly improved chemical stability. (S)-Nipecotic acid derivatives possessing a 2-[1-(4-methoxy-2-methylphenyl)-1,1-bis(4-methoxyphenyl)methoxy]ethyl (DDPM-859) or a 4,4,4-tris(4-methoxyphenyl)but-2-en-1-yl moiety (DDPM-1457) were found to exhibit pIC(50) values of 5.78 and 5.87, respectively. Thus, as mGAT4 inhibitors, these compounds compare well with (S)-SNAP-5114 (pIC(50) =5.71), but are far more stable than the latter. Moreover, DDPM-859 displays a more favorable subtype selectivity for mGAT4 versus MGAT3 than does (S)-SNAP-5114.
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Development of an (S)-1-{2-[tris(4-methoxyphenyl)methoxy]ethyl}piperidine-3-carboxylic acid [(S)-SNAP-5114] carba analogue inhibitor for murine γ-aminobutyric acid transporter type 4.
ChemMedChem, 2012Co-Authors: Jorg Pabel, Lars Allmendinger, Georg Höfner, Mark Faust, Cornelia Prehn, Babette Worlein, Klaus T. WannerAbstract:A series of GABA uptake inhibitors related to (S)-1-{2-[tris(4-methoxyphenyl)methoxy]ethyl}piperidine-3-carboxylic acid [(S)-SNAP-5114], the most potent mGAT4 inhibitor known so far, were synthesized and biologically evaluated for their inhibitory potency at the four GABA uptake transporters mGAT1-4 stably expressed in HEK-293 cell lines. New analogues were developed with potencies that are similar to or slightly higher than those of current mGAT4 inhibitors, but with distinctly improved chemical stability. (S)-Nipecotic acid derivatives possessing a 2-[1-(4-methoxy-2-methylphenyl)-1,1-bis(4-methoxyphenyl)methoxy]ethyl (DDPM-859) or a 4,4,4-tris(4-methoxyphenyl)but-2-en-1-yl moiety (DDPM-1457) were found to exhibit pIC(50) values of 5.78 and 5.87, respectively. Thus, as mGAT4 inhibitors, these compounds compare well with (S)-SNAP-5114 (pIC(50) =5.71), but are far more stable than the latter. Moreover, DDPM-859 displays a more favorable subtype selectivity for mGAT4 versus MGAT3 than does (S)-SNAP-5114.
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Development of imidazole alkanoic acids as MGAT3 selective GABA uptake inhibitors.
European journal of medicinal chemistry, 2011Co-Authors: Silke Hack, Georg Höfner, Jorg Pabel, Babette Worlein, Klaus T. WannerAbstract:Abstract A new series of potential GABA uptake inhibitors starting from of 1H-imidazol-4-ylacetic acid with the carboxylic acid side chain originating from different positions and varying in length have been synthesized and tested for the inhibitory potency at the four GABA uptake transporters mGAT1–4 stably expressed in HEK cells. Further two bicyclic compounds with a rigidified carboxylic acid side chain were included in this study. The results of the biological tests indicated that most ω-imidazole alkanoic and alkenoic acid derivatives exhibit the highest potencies as GABA uptake inhibitors at MGAT3.