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(1 - 12 of 12)
- Title
- An S116R Phosphorylation Site Mutation in Human Fibroblast Growth Factor-1 Differentially Affects Mitogenic and Glucose-Lowering Activities.
- Creator
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Xia, Xue, Kumru, Ozan S, Blaber, Sachiko I, Middaugh, C Russell, Li, Ling, Ornitz, David M, Suh, Jae Myoung, Atkins, Annette R, Downes, Michael, Evans, Ronald M, Tenorio, Connie...
Show moreXia, Xue, Kumru, Ozan S, Blaber, Sachiko I, Middaugh, C Russell, Li, Ling, Ornitz, David M, Suh, Jae Myoung, Atkins, Annette R, Downes, Michael, Evans, Ronald M, Tenorio, Connie A, Bienkiewicz, Ewa, Blaber, Michael
Show less - Abstract/Description
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Fibroblast growth factor-1 (FGF-1), a potent human mitogen and insulin sensitizer, signals through both tyrosine kinase receptor-mediated autocrine/paracrine pathways as well as a nuclear intracrine pathway. Phosphorylation of FGF-1 at serine 116 (S116) has been proposed to regulate intracrine signaling. Position S116 is located within a ∼17 amino acid C-terminal loop that contains a rich set of functional determinants including heparin∖heparan sulfate affinity, thiol reactivity, nuclear...
Show moreFibroblast growth factor-1 (FGF-1), a potent human mitogen and insulin sensitizer, signals through both tyrosine kinase receptor-mediated autocrine/paracrine pathways as well as a nuclear intracrine pathway. Phosphorylation of FGF-1 at serine 116 (S116) has been proposed to regulate intracrine signaling. Position S116 is located within a ∼17 amino acid C-terminal loop that contains a rich set of functional determinants including heparin∖heparan sulfate affinity, thiol reactivity, nuclear localization, pharmacokinetics, functional half-life, nuclear ligand affinity, stability, and structural dynamics. Mutational targeting of specific functionality in this region without perturbing other functional determinants is a design challenge. S116R is a non-phosphorylatable variant present in bovine FGF-1 and other members of the human FGF family. We show that the S116R mutation in human FGF-1 is accommodated with no perturbation of biophysical or structural properties, and is therefore an attractive mutation with which to elucidate the functional role of phosphorylation. Characterization of S116R shows reduction in NIH 3T3 fibroblast mitogenic stimulation, increase in fibroblast growth factor receptor-1c activation, and prolonged duration of glucose lowering in ob/ob hyperglycemic mice. A novel FGF-1/fibroblast growth factor receptor-1c dimerization interaction combined with non-phosphorylatable intracrine signaling is hypothesized to be responsible for these observed functional effects.
Show less - Date Issued
- 2016-12-01
- Identifier
- FSU_pmch_27773526, 10.1016/j.xphs.2016.09.005, PMC5310217, 27773526, 27773526, S0022-3549(16)41698-9
- Format
- Citation
- Title
- Akt mediated phosphorylation of LARP6; critical step in biosynthesis of type I collagen.
- Creator
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Zhang, Yujie, Stefanovic, Branko
- Abstract/Description
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La ribonucleoprotein domain family, member 6 (LARP6) is the RNA binding protein, which regulates translation of collagen mRNAs and synthesis of type I collagen. Posttranslational modifications of LARP6 and how they affect type I collagen synthesis have not been studied. We show that in lung fibroblasts LARP6 is phosphorylated at 8 serines, 6 of which are located within C-terminal domain. Phosphorylation of LARP6 follows a hierarchical order; S451 phosphorylation being a prerequisite for...
Show moreLa ribonucleoprotein domain family, member 6 (LARP6) is the RNA binding protein, which regulates translation of collagen mRNAs and synthesis of type I collagen. Posttranslational modifications of LARP6 and how they affect type I collagen synthesis have not been studied. We show that in lung fibroblasts LARP6 is phosphorylated at 8 serines, 6 of which are located within C-terminal domain. Phosphorylation of LARP6 follows a hierarchical order; S451 phosphorylation being a prerequisite for phosphorylations of other serines. Inhibition of PI3K/Akt pathway reduced the phosphorylation of LARP6, but had no effect on the S451A mutant, suggesting that PI3K/Akt pathway targets S451 and we have identified Akt as the responsible kinase. Overexpression of S451A mutant had dominant negative effect on collagen biosynthesis; drastically reduced secretion of collagen and induced hyper-modifications of collagen α2 (I) polypeptides. This indicates that LARP6 phosphorylation at S451 is critical for regulating translation and folding of collagen polypeptides. Akt inhibitor, GSK-2141795, which is in clinical trials for treatment of solid tumors, reduced collagen production by human lung fibroblasts with EC50 of 150 nM. This effect can be explained by inhibition of LARP6 phosphorylation and suggests that Akt inhibitors may be effective in treatment of various forms of fibrosis.
Show less - Date Issued
- 2016-03-02
- Identifier
- FSU_pmch_26932461, 10.1038/srep22597, PMC4773855, 26932461, 26932461, srep22597
- Format
- Citation
- Title
- Rootletin organizes the ciliary rootlet to achieve neuron sensory function in Drosophila.
- Creator
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Chen, Jieyan V, Kao, Ling-Rong, Jana, Swadhin C, Sivan-Loukianova, Elena, Mendonça, Susana, Cabrera, Oscar A, Singh, Priyanka, Cabernard, Clemens, Eberl, Daniel F, Bettencourt...
Show moreChen, Jieyan V, Kao, Ling-Rong, Jana, Swadhin C, Sivan-Loukianova, Elena, Mendonça, Susana, Cabrera, Oscar A, Singh, Priyanka, Cabernard, Clemens, Eberl, Daniel F, Bettencourt-Dias, Monica, Megraw, Timothy L
Show less - Abstract/Description
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Cilia are essential for cell signaling and sensory perception. In many cell types, a cytoskeletal structure called the ciliary rootlet links the cilium to the cell body. Previous studies indicated that rootlets support the long-term stability of some cilia. Here we report that Drosophila melanogaster Rootletin (Root), the sole orthologue of the mammalian paralogs Rootletin and C-Nap1, assembles into rootlets of diverse lengths among sensory neuron subtypes. Root mutant neurons lack rootlets...
Show moreCilia are essential for cell signaling and sensory perception. In many cell types, a cytoskeletal structure called the ciliary rootlet links the cilium to the cell body. Previous studies indicated that rootlets support the long-term stability of some cilia. Here we report that Drosophila melanogaster Rootletin (Root), the sole orthologue of the mammalian paralogs Rootletin and C-Nap1, assembles into rootlets of diverse lengths among sensory neuron subtypes. Root mutant neurons lack rootlets and have dramatically impaired sensory function, resulting in behavior defects associated with mechanosensation and chemosensation. Root is required for cohesion of basal bodies, but the cilium structure appears normal in Root mutant neurons. We show, however, that normal rootlet assembly requires centrioles. The N terminus of Root contains a conserved domain and is essential for Root function in vivo. Ectopically expressed Root resides at the base of mother centrioles in spermatocytes and localizes asymmetrically to mother centrosomes in neuroblasts, both requiring Bld10, a basal body protein with varied functions.
Show less - Date Issued
- 2015-10-26
- Identifier
- FSU_pmch_26483560, 10.1083/jcb.201502032, PMC4621839, 26483560, 26483560, jcb.201502032
- Format
- Citation
- Title
- Drosophila pericentrin requires interaction with calmodulin for its function at centrosomes and neuronal basal bodies but not at sperm basal bodies.
- Creator
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Galletta, Brian J, Guillen, Rodrigo X, Fagerstrom, Carey J, Brownlee, Chris W, Lerit, Dorothy A, Megraw, Timothy L, Rogers, Gregory C, Rusan, Nasser M
- Abstract/Description
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Pericentrin is a critical centrosomal protein required for organizing pericentriolar material (PCM) in mitosis. Mutations in pericentrin cause the human genetic disorder Majewski/microcephalic osteodysplastic primordial dwarfism type II, making a detailed understanding of its regulation extremely important. Germaine to pericentrin's function in organizing PCM is its ability to localize to the centrosome through the conserved C-terminal PACT domain. Here we use Drosophila pericentrin-like...
Show morePericentrin is a critical centrosomal protein required for organizing pericentriolar material (PCM) in mitosis. Mutations in pericentrin cause the human genetic disorder Majewski/microcephalic osteodysplastic primordial dwarfism type II, making a detailed understanding of its regulation extremely important. Germaine to pericentrin's function in organizing PCM is its ability to localize to the centrosome through the conserved C-terminal PACT domain. Here we use Drosophila pericentrin-like-protein (PLP) to understand how the PACT domain is regulated. We show that the interaction of PLP with calmodulin (CaM) at two highly conserved CaM-binding sites in the PACT domain controls the proper targeting of PLP to the centrosome. Disrupting the PLP-CaM interaction with single point mutations renders PLP inefficient in localizing to centrioles in cultured S2 cells and Drosophila neuroblasts. Although levels of PCM are unaffected, it is highly disorganized. We also demonstrate that basal body formation in the male testes and the production of functional sperm does not rely on the PLP-CaM interaction, whereas production of functional mechanosensory neurons does.
Show less - Date Issued
- 2014-09-15
- Identifier
- FSU_pmch_25031429, 10.1091/mbc.E13-10-0617, PMC4161505, 25031429, 25031429, mbc.E13-10-0617
- Format
- Citation
- Title
- Characterization of binding of LARP6 to the 5' stem-loop of collagen mRNAs: implications for synthesis of type I collagen..
- Creator
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Stefanovic, Lela, Longo, Liam, Zhang, Yujie, Stefanovic, Branko
- Abstract/Description
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Type I collagen is composed of 2 polypeptides, α1(I) and α2(I), which fold into triple helix. Collagen α1(I) and α2(I) mRNAs have a conserved stem-loop structure in their 5' UTRs, the 5'SL. LARP6 binds the 5'SL to regulate type I collagen expression. We show that 5 nucleotides within the single stranded regions of 5'SL contribute to the high affinity of LARP6 binding. Mutation of individual nucleotides abolishes the binding in gel mobility shift assay. LARP6 binding to 5'SL of collagen α2(I)...
Show moreType I collagen is composed of 2 polypeptides, α1(I) and α2(I), which fold into triple helix. Collagen α1(I) and α2(I) mRNAs have a conserved stem-loop structure in their 5' UTRs, the 5'SL. LARP6 binds the 5'SL to regulate type I collagen expression. We show that 5 nucleotides within the single stranded regions of 5'SL contribute to the high affinity of LARP6 binding. Mutation of individual nucleotides abolishes the binding in gel mobility shift assay. LARP6 binding to 5'SL of collagen α2(I) mRNA is more stable than the binding to 5'SL of α1(I) mRNA, although the equilibrium binding constants are similar. The more stable binding to α2(I) mRNA may favor synthesis of the heterotrimeric type I collagen. LARP6 needs 2 domains to contact 5'SL, the La domain and the RRM. T133 in the La domain is critical for folding of the protein, while loop 3 in the RRM is critical for binding 5'SL. Loop 3 is also involved in the interaction of LARP6 and protein translocation channel SEC61. This interaction is essential for type I collagen synthesis, because LARP6 mutant which binds 5'SL but which does not interact with SEC61, suppresses collagen synthesis in a dominant negative manner. We postulate that LARP6 directly targets collagen mRNAs to the SEC61 translocons to facilitate coordinated translation of the 2 collagen mRNAs. The unique sequences of LARP6 identified in this work may have evolved to enable its role in type I collagen biosynthesis.
Show less - Date Issued
- 2014-01-01
- Identifier
- FSU_pmch_25692237, 10.1080/15476286.2014.996467, PMC4615758, 25692237, 25692237
- Format
- Citation
- Title
- δ/ω-Plectoxin-Pt1a: an excitatory spider toxin with actions on both Ca(2+) and Na(+) channels..
- Creator
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Zhou, Yi, Zhao, Mingli, Fields, Gregg B, Wu, Chun-Fang, Branton, W Dale
- Abstract/Description
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The venom of spider Plectreurys tristis contains a variety of peptide toxins that selectively target neuronal ion channels. O-palmitoylation of a threonine or serine residue, along with a characteristic and highly constrained disulfide bond structure, are hallmarks of a family of toxins found in this venom. Here, we report the isolation and characterization of a new toxin, δ/ω-plectoxin-Pt1a, from this spider venom. It is a 40 amino acid peptide containing an O-palmitoylated Ser-39. Analysis...
Show moreThe venom of spider Plectreurys tristis contains a variety of peptide toxins that selectively target neuronal ion channels. O-palmitoylation of a threonine or serine residue, along with a characteristic and highly constrained disulfide bond structure, are hallmarks of a family of toxins found in this venom. Here, we report the isolation and characterization of a new toxin, δ/ω-plectoxin-Pt1a, from this spider venom. It is a 40 amino acid peptide containing an O-palmitoylated Ser-39. Analysis of δ/ω-plectoxin-Pt1a cDNA reveals a small precursor containing a secretion signal sequence, a 14 amino acid N-terminal propeptide, and a C-terminal amidation signal. The biological activity of δ/ω-plectoxin-Pt1a is also unique. It preferentially blocks a subset of Ca(2+) channels that is apparently not required for neurotransmitter release; decreases threshold for Na(+) channel activation; and slows Na(+) channel inactivation. As δ/ω-plectoxin-Pt1a enhances synaptic transmission by prolonging presynaptic release of neurotransmitter, its effects on Na(+) and Ca(2+) channels may act synergistically to sustain the terminal excitability.
Show less - Date Issued
- 2013-05-14
- Identifier
- FSU_pmch_23691198, 10.1371/journal.pone.0064324, PMC3653879, 23691198, 23691198, PONE-D-13-04611
- Format
- Citation
- Title
- Phosphorylation of the transcription factor YY1 by CK2α prevents cleavage by caspase 7 during apoptosis.
- Creator
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Riman, Sarah, Rizkallah, Raed, Kassardjian, Ari, Alexander, Karen E, Lüscher, Bernhard, Hurt, Myra M
- Abstract/Description
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In this report, we describe the phosphorylation of Yin Yang 1 (YY1) in vitro and in vivo by CK2α (casein kinase II), a multifunctional serine/threonine protein kinase. YY1 is a ubiquitously expressed multifunctional zinc finger transcription factor implicated in regulation of many cellular and viral genes. The products of these genes are associated with cell growth, the cell cycle, development, and differentiation. Numerous studies have linked YY1 to tumorigenesis and apoptosis. YY1 is a...
Show moreIn this report, we describe the phosphorylation of Yin Yang 1 (YY1) in vitro and in vivo by CK2α (casein kinase II), a multifunctional serine/threonine protein kinase. YY1 is a ubiquitously expressed multifunctional zinc finger transcription factor implicated in regulation of many cellular and viral genes. The products of these genes are associated with cell growth, the cell cycle, development, and differentiation. Numerous studies have linked YY1 to tumorigenesis and apoptosis. YY1 is a target for cleavage by caspases in vitro and in vivo as well, but very little is known about the mechanisms that regulate its cleavage during apoptosis. Here, we identify serine 118 in the transactivation domain of YY1 as the site of CK2α phosphorylation, proximal to a caspase 7 cleavage site. CK2α inhibitors, as well as knockdown of CK2α by small interfering RNA, reduce S118 phosphorylation in vivo and enhance YY1 cleavage under apoptotic conditions, whereas increased CK2α activity by overexpression in vivo elevates S118 phosphorylation. A serine-to-alanine substitution at serine 118 also increases the cleavage of YY1 during apoptosis compared to wild-type YY1. Taken together, we have discovered a regulatory link between YY1 phosphorylation at serine 118 and regulation of its cleavage during programmed cell death.
Show less - Date Issued
- 2012-02-01
- Identifier
- FSU_pmch_22184066, 10.1128/MCB.06466-11, PMC3272974, 22184066, 22184066, MCB.06466-11
- Format
- Citation
- Title
- The transcription factor YY1 is a novel substrate for Aurora B kinase at G2/M transition of the cell cycle.
- Creator
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Kassardjian, Ari, Rizkallah, Raed, Riman, Sarah, Renfro, Samuel H, Alexander, Karen E, Hurt, Myra M
- Abstract/Description
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Yin Yang 1 (YY1) is a ubiquitously expressed and highly conserved multifunctional transcription factor that is involved in a variety of cellular processes. Many YY1-regulated genes have crucial roles in cell proliferation, differentiation, apoptosis, and cell cycle regulation. Numerous mechanisms have been shown to regulate the function of YY1, such as DNA binding affinity, subcellular localization, and posttranslational modification including phosphorylation. Polo-like kinase 1(Plk1) and...
Show moreYin Yang 1 (YY1) is a ubiquitously expressed and highly conserved multifunctional transcription factor that is involved in a variety of cellular processes. Many YY1-regulated genes have crucial roles in cell proliferation, differentiation, apoptosis, and cell cycle regulation. Numerous mechanisms have been shown to regulate the function of YY1, such as DNA binding affinity, subcellular localization, and posttranslational modification including phosphorylation. Polo-like kinase 1(Plk1) and Casein kinase 2α (CK2 α) were the first two kinases identified to phosphorylate YY1. In this study, we identify a third kinase. We report that YY1 is a novel substrate of the Aurora B kinase both in vitro and in vivo. Serine 184 phosphorylation of YY1 by Aurora B is cell cycle regulated and peaks at G2/M and is rapidly dephosphorylated, likely by protein phosphatase 1 (PP1) as the cells enter G1. Aurora A and Aurora C can also phosphorylate YY1 in vitro, but at serine/threonine residues other than serine 184. We present evidence that phosphorylation of YY1 in the central glycine/alanine (G/A)-rich region is important for DNA binding activity, with a potential phosphorylation/acetylation interplay regulating YY1 function. Given their importance in mitosis and overexpression in human cancers, Aurora kinases have been identified as promising therapeutic targets. Increasing our understanding of Aurora substrates will add to the understanding of their signaling pathways.
Show less - Date Issued
- 2012-01-01
- Identifier
- FSU_pmch_23226345, 10.1371/journal.pone.0050645, PMC3511337, 23226345, 23226345, PONE-D-12-19550
- Format
- Citation
- Title
- Intracellular regions of the Eag potassium channel play a critical role in generation of voltage-dependent currents.
- Creator
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Li, Yong, Liu, Xinqiu, Wu, Yuying, Xu, Zhe, Li, Hongqin, Griffith, Leslie C, Zhou, Yi
- Abstract/Description
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Folding, assembly, and trafficking of ion channels are tightly controlled processes and are important for biological functions relevant to health and disease. Here, we report that functional expression of the Eag channel is temperature-sensitive by a mechanism that is independent of trafficking or surface targeting of the channel protein. Eag channels in cells grown at 37 °C exhibit voltage-evoked gating charge movements but fail to conduct K(+) ions. By mutagenesis and chimeric channel...
Show moreFolding, assembly, and trafficking of ion channels are tightly controlled processes and are important for biological functions relevant to health and disease. Here, we report that functional expression of the Eag channel is temperature-sensitive by a mechanism that is independent of trafficking or surface targeting of the channel protein. Eag channels in cells grown at 37 °C exhibit voltage-evoked gating charge movements but fail to conduct K(+) ions. By mutagenesis and chimeric channel studies, we show that the N- and C-terminal regions are involved in controlling a step after movement of the voltage sensor, as well as in regulating biophysical properties of the Eag channel. Synthesis and assembly of Eag at high temperature disrupt the ability of these domains to carry out their function. These results suggest an important role of the intracellular regions in the generation of Eag currents.
Show less - Date Issued
- 2011-01-14
- Identifier
- FSU_pmch_21059657, 10.1074/jbc.M110.184077, PMC3020747, 21059657, 21059657, M110.184077
- Format
- Citation
- Title
- Intracellular linkers are involved in Mg2+-dependent modulation of the Eag potassium channel.
- Creator
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Liu, Xinqiu, Wu, Yuying, Zhou, Yi
- Abstract/Description
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Modulation of activation kinetics by divalent ions is one of the characteristic features of Eag channels. Here, we report that Mg(2+)-dependent deceleration of Eag channel activation is significantly attenuated by a G297E mutation, which exhibits a gain-of-function phenotype in Drosophila by suppressing the effect of shaker mutation on behavior and neuronal excitability. The G297 residue is located in the intracellular linker of transmembrane segments S2 and S3, and is thus not involved in...
Show moreModulation of activation kinetics by divalent ions is one of the characteristic features of Eag channels. Here, we report that Mg(2+)-dependent deceleration of Eag channel activation is significantly attenuated by a G297E mutation, which exhibits a gain-of-function phenotype in Drosophila by suppressing the effect of shaker mutation on behavior and neuronal excitability. The G297 residue is located in the intracellular linker of transmembrane segments S2 and S3, and is thus not involved in direct binding of Mg(2+) ions. Moreover, mutation of the only positively charged residue in the other intracellular linker between S4 and S5 also results in a dramatic reduction of Mg(2+)-dependent modulation of Eag activation kinetics. Collectively, the two mutations in eag eliminate or even paradoxically reverse the effect of Mg(2+) on channel activation and inactivation kinetics. Together, these results suggest an important role of the intracellular linker regions in gating processes of Eag channels.
Show less - Date Issued
- 2010-07-01
- Identifier
- FSU_pmch_20855938, 10.4161/chan.4.4.12329, PMC3322480, 20855938, 20855938, 12329
- Format
- Citation
- Title
- Regulation of the transcription factor YY1 in mitosis through phosphorylation of its DNA-binding domain.
- Creator
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Rizkallah, Raed, Hurt, Myra M
- Abstract/Description
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Yin-Yang 1 (YY1) is a ubiquitously expressed zinc finger transcription factor. It regulates a vast array of genes playing critical roles in development, differentiation, and cell cycle. Very little is known about the mechanisms that regulate the functions of YY1. It has long been proposed that YY1 is a phosphoprotein; however, a direct link between phosphorylation and the function of YY1 has never been proven. Investigation of the localization of YY1 during mitosis shows that it is...
Show moreYin-Yang 1 (YY1) is a ubiquitously expressed zinc finger transcription factor. It regulates a vast array of genes playing critical roles in development, differentiation, and cell cycle. Very little is known about the mechanisms that regulate the functions of YY1. It has long been proposed that YY1 is a phosphoprotein; however, a direct link between phosphorylation and the function of YY1 has never been proven. Investigation of the localization of YY1 during mitosis shows that it is distributed to the cytoplasm during prophase and remains excluded from DNA until early telophase. Immunostaining studies show that YY1 is distributed equally between daughter cells and rapidly associates with decondensing chromosomes in telophase, suggesting a role for YY1 in early marking of active and repressed genes. The exclusion of YY1 from DNA in prometaphase HeLa cells correlated with an increase in the phosphorylation of YY1 and loss of DNA-binding activity that can be reversed by dephosphorylation. We have mapped three phosphorylation sites on YY1 during mitosis and show that phosphorylation of two of these sites can abolish the DNA-binding activity of YY1. These results demonstrate a novel mechanism for the inactivation of YY1 through phosphorylation of its DNA-binding domain.
Show less - Date Issued
- 2009-11-01
- Identifier
- FSU_pmch_19793915, 10.1091/mbc.E09-04-0264, PMC2777106, 19793915, 19793915, E09-04-0264
- Format
- Citation
- Title
- Tet 42, a novel tetracycline resistance determinant isolated from deep terrestrial subsurface bacteria.
- Creator
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Brown, Mindy G, Mitchell, Elizabeth H, Balkwill, David L
- Abstract/Description
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Tet 42, a novel tetracycline resistance determinant from deep subsurface bacteria, was characterized and found to have a 30% sequence similarity to TetA(Z). The protein is a putative efflux pump that shares characteristics with previously characterized pumps, including a divergently transcribed TetR repressor, a conserved GxxSDRxGRR motif, and transmembrane domains.
- Date Issued
- 2008-12-01
- Identifier
- FSU_pmch_18809935, 10.1128/AAC.00640-08, PMC2592862, 18809935, 18809935, AAC.00640-08
- Format
- Citation
