scholarly journals HNF4α isoforms regulate the circadian balance between carbohydrate and lipid metabolism in the liver

2021 ◽  
Author(s):  
Jonathan R Deans ◽  
Poonamjot Deol ◽  
Nina Titova ◽  
Sarah H Radi ◽  
Linh M Vuong ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Ketone Bodies ◽  
Fetal Liver ◽  
Hepatocyte Nuclear Factor ◽  
Hepatocyte Differentiation ◽  
Protein Protein Interactions ◽  
Adult Liver ◽  
Carbohydrate And Lipid Metabolism ◽  
Evolutionarily Conserved ◽  
Hepatocyte Nuclear Factor 4Α

Hepatocyte Nuclear Factor 4α (HNF4α), a master regulator of hepatocyte differentiation, is regulated by two promoters (P1 and P2). P1-HNF4α is the major isoform in the adult liver while P2-HNF4α is thought to be expressed only in fetal liver and liver cancer. Here, we show that P2-HNF4α is expressed at ZT9 and ZT21 in the normal adult liver and orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions. We demonstrate that while P1-HNF4α drives gluconeogenesis, P2-HNF4α drives ketogenesis and is required for elevated levels of ketone bodies in females. Exon swap mice expressing only P2- HNF4α exhibit subtle differences in circadian gene regulation and disruption of the clock increases expression of P2-HNF4α. Taken together, we propose that the highly conserved two-promoter structure of the Hnfa gene is an evolutionarily conserved mechanism to maintain the balance between gluconeogenesis and ketogenesis in the liver in a circadian fashion.

scholarly journals β-Catenin is a pH sensor with decreased stability at higher intracellular pH

2018 ◽  
Vol 217 (11) ◽  
pp. 3965-3976 ◽  
Author(s):  
Katharine A. White ◽  
Bree K. Grillo-Hill ◽  
Mario Esquivel ◽  
Jobelle Peralta ◽  
Vivian N. Bui ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Protein Interactions ◽  
Mammalian Cells ◽  
Ph Sensor ◽  
Adherens Junction ◽  
Protein Protein Interactions ◽  
Adherens Junction Protein ◽  
Junction Protein ◽  
Evolutionarily Conserved ◽  
Ph Dependent

β-Catenin functions as an adherens junction protein for cell–cell adhesion and as a signaling protein. β-catenin function is dependent on its stability, which is regulated by protein–protein interactions that stabilize β-catenin or target it for proteasome-mediated degradation. In this study, we show that β-catenin stability is regulated by intracellular pH (pHi) dynamics, with decreased stability at higher pHi in both mammalian cells and Drosophila melanogaster. β-Catenin degradation requires phosphorylation of N-terminal residues for recognition by the E3 ligase β-TrCP. While β-catenin phosphorylation was pH independent, higher pHi induced increased β-TrCP binding and decreased β-catenin stability. An evolutionarily conserved histidine in β-catenin (found in the β-TrCP DSGIHS destruction motif) is required for pH-dependent binding to β-TrCP. Expressing a cancer-associated H36R–β-catenin mutant in the Drosophila eye was sufficient to induce Wnt signaling and produced pronounced tumors not seen with other oncogenic β-catenin alleles. We identify pHi dynamics as a previously unrecognized regulator of β-catenin stability, functioning in coincidence with phosphorylation.

Protein-Protein Interactions in the Tetraspanin Web

Physiology ◽  
2005 ◽  
Vol 20 (4) ◽  
pp. 218-224 ◽  
Author(s):  
Shoshana Levy ◽  
Tsipi Shoham
Keyword(s):  
Signal Transduction ◽  
Cell Proliferation ◽  
Protein Interactions ◽  
Membrane Microdomains ◽  
Protein Protein Interactions ◽  
Host Parasite Interactions ◽  
Evolutionarily Conserved ◽  
And Migration ◽  
Host Parasite ◽  
Partner Proteins

Tetraspanins are evolutionarily conserved membrane proteins that tend to associate laterally with one another and to cluster dynamically with numerous partner proteins in membrane microdomains. Consequently, members of this family are involved in the coordination of intracellular and intercellular processes, including signal transduction; cell proliferation, adhesion, and migration; cell fusion; and host-parasite interactions.

One Hippo and many masters: differential regulation of the Hippo pathway in cancer

2014 ◽  
Vol 42 (4) ◽  
pp. 816-821 ◽  
Author(s):  
David Romano ◽  
David Matallanas ◽  
Dennie T. Frederick ◽  
Keith T. Flaherty ◽  
Walter Kolch
Keyword(s):  
Protein Interactions ◽  
Hippo Pathway ◽  
Promoter Hypermethylation ◽  
Protein Protein Interactions ◽  
Evolutionarily Conserved ◽  
Or Gene ◽  
Phosphoinositide 3 Kinase ◽  
Ras Isoforms ◽  
The Hippo Pathway

The Hippo/MST2 (mammalian sterile 20-like kinase 2) pathway is a signalling cascade evolutionarily conserved in its structure. Originally described in Drosophila melanogaster as a regulator of organ size, this pathway has greater functions in mammals. Disturbance of mammalian MST2 pathway is associated with tumorigenesis by affecting apoptosis, cell cycle and polarity. In addition, this pathway has been shown to cross-talk with mitogenic pathways at multiple levels. In the present mini-review, we discuss our contribution highlighting the regulation of MST2 signalling by frequently observed oncogenic perturbations affecting mitogenic pathways. In particular, we review the role of RAS isoforms and PI3K (phosphoinositide 3-kinase)/Akt in the regulation of MST2 activity by phosphorylation. We also put the emphasis on RAF-induced control of MST2 signalling by protein–protein interactions. Finally, we recapitulate some of the direct mechanisms, such as ubiquitin-dependent degradation or gene silencing by promoter hypermethylation, involved in MST2 pathway component down-regulation in cancers.

scholarly journals SMC proteins and chromosome mechanics: from bacteria to humans

2005 ◽  
Vol 360 (1455) ◽  
pp. 507-514 ◽  
Author(s):  
Tatsuya Hirano
Keyword(s):  
Protein Interactions ◽  
Protein Complexes ◽  
Related Protein ◽  
Protein Protein Interactions ◽  
The Core ◽  
Archaeal Species ◽  
Evolutionarily Conserved ◽  
Structural Maintenance Of Chromosomes ◽  
Mitosis And Meiosis ◽  
Smc Proteins

Chromosome cohesion and condensation are essential prerequisites of proper segregation of genomes during mitosis and meiosis, and are supported by two structurally related protein complexes, cohesin and condensin, respectively. At the core of the two complexes lie members of the structural maintenance of chromosomes (SMC) family of ATPases. SMC proteins are also found in most bacterial and archaeal species, implicating the existence of an evolutionarily conserved theme of higher-order chromosome organization and dynamics. SMC dimers adopt a two-armed structure with an ATP-binding cassette (ABC)-like domain at the distal end of each arm. This article reviews recent work on the bacterial and eukaryotic SMC protein complexes, and discusses current understanding of how these uniquely designed protein machines may work at a mechanistic level. It seems most likely that the action of SMC proteins is highly dynamic and plastic, possibly involving a diverse array of intramolecular and intermolecular protein–protein interactions.

scholarly journals Hepatocyte-specific deletion of hepatocyte nuclear factor-4α in adult mice results in increased hepatocyte proliferation

2013 ◽  
Vol 304 (1) ◽  
pp. G26-G37 ◽  
Author(s):  
Chad Walesky ◽  
Sumedha Gunewardena ◽  
Ernest F. Terwilliger ◽  
Genea Edwards ◽  
Prachi Borude ◽  
...  
Keyword(s):  
Gene Expression ◽  
Target Genes ◽  
Viral Vector ◽  
Hepatocyte Proliferation ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Hepatocyte Differentiation ◽  
Hepatic Differentiation ◽  
Hepatocyte Nuclear Factor 4Α ◽  
Specific Deletion

Hepatocyte nuclear factor-4α (HNF4α) is known as the master regulator of hepatocyte differentiation. Recent studies indicate that HNF4α may inhibit hepatocyte proliferation via mechanisms that have yet to be identified. Using a HNF4α knockdown mouse model based on delivery of inducible Cre recombinase via an adeno-associated virus 8 viral vector, we investigated the role of HNF4α in the regulation of hepatocyte proliferation. Hepatocyte-specific deletion of HNF4α resulted in increased hepatocyte proliferation. Global gene expression analysis showed that a majority of the downregulated genes were previously known HNF4α target genes involved in hepatic differentiation. Interestingly, ≥500 upregulated genes were associated with cell proliferation and cancer. Furthermore, we identified potential negative target genes of HNF4α, many of which are involved in the stimulation of proliferation. Using chromatin immunoprecipitation analysis, we confirmed binding of HNF4α at three of these genes. Furthermore, overexpression of HNF4α in mouse hepatocellular carcinoma cells resulted in a decrease in promitogenic gene expression and cell cycle arrest. Taken together, these data indicate that, apart from its role in hepatocyte differentiation, HNF4α actively inhibits hepatocyte proliferation by repression of specific promitogenic genes.

The Drosophila pipsqueak gene encodes a nuclear BTB-domain-containing protein required early in oogenesis

Development ◽  
1996 ◽  
Vol 122 (6) ◽  
pp. 1859-1871 ◽  
Author(s):  
H. Horowitz ◽  
C.A. Berg
Keyword(s):  
Fusion Protein ◽  
Protein Interactions ◽  
Protein Isoforms ◽  
Follicle Cells ◽  
Protein Protein Interactions ◽  
Gene Encoding ◽  
Btb Domain ◽  
Multiple Transcripts ◽  
C Terminus ◽  
Evolutionarily Conserved

Mutations at the pipsqueak locus affect early patterning in the Drosophila egg and embryo. We have cloned pipsqueak and found that it is a large and complex gene, encoding multiple transcripts and protein isoforms. One protein, PsqA, is absent in all of the mutants that we have examined. We show that PsqA is a nuclear protein present in the germ cells and somatically derived follicle cells throughout oogenesis and that it is required prior to stage one of oogenesis. PsqA contains a BTB (POZ) domain at its amino terminus; additionally, we have identified an evolutionarily conserved motif of unknown function present four times in tandem at the C terminus of the protein. PZ pipsqueak mutants produce a putative fusion protein containing the pipsqueak BTB domain fused to sequences resident on the PZ element (H. Horowitz and C. Berg, 1995 Genetics 139, 327–335). We demonstrate here that expression of this fusion protein in wild-type flies has a dominant effect, resulting in infertility and eggshell defects. These dominant phenotypes are discussed in light of current theories on the role of the BTB domain in protein-protein interactions.

scholarly journals The nematode homologue of Mediator complex subunit 28, F28F8.5, is a critical regulator of C. elegans development

2016 ◽  
Author(s):  
Markéta Kostrouchová ◽  
David Kostrouch ◽  
Ahmed A Chughtai ◽  
Filip Kaššák ◽  
Jan P. Novotný ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Protein Interactions ◽  
Structural Proteins ◽  
Mediator Complex ◽  
Cytoplasmic Localization ◽  
Protein Protein Interactions ◽  
C Elegans ◽  
Evolutionarily Conserved ◽  
Nuclear Events ◽  
Bona Fide

The evolutionarily conserved Mediator complex is a critical player in regulating transcription. Comprised of approximately two dozen proteins, Mediator integrates diverse regulatory signals through direct protein-protein interactions that, in turn, modulate the influence of Mediator on RNA Polymerase II activity. One Mediator subunit, MED28, is known to interact with cytoplasmic structural proteins, providing a potential direct link between cytoplasmic dynamics and the control of gene transcription. Although identified in many animals and plants, MED28 is not present in yeast; no bona fide MED28 has been described previously in C. elegans. Here, we identify bioinformatically F28F8.5, an uncharacterized predicted protein, as the nematode homologue of MED28. As in other metazoa, F28F8.5 has dual nuclear and cytoplasmic localization and plays critical roles in the regulation of development. F28F8.5 is a vital gene and its null mutants have severely malformed gonads and do not reproduce. Our results indicate that F28F8.5 is a homologue of MED28 and suggest that the potential to link cytoplasmic and nuclear events is conserved between MED28 vertebrate and nematode homologues.

scholarly journals Hepatocyte nuclear factor-4alpha mediates the stimulatory effect of peroxisome proliferator-activated receptor gamma co-activator-1alpha (PGC-1alpha) on glucose-6-phosphatase catalytic subunit gene transcription in H4IIE cells

2003 ◽  
Vol 369 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Jared N. BOUSTEAD ◽  
Beth T. STADELMAIER ◽  
Angela M. EEDS ◽  
Peter O. WIEBE ◽  
Christina A. SVITEK ◽  
...  
Keyword(s):  
Fusion Gene ◽  
Catalytic Subunit ◽  
Peroxisome Proliferator ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Peroxisome Proliferator Activated Receptor ◽  
H4iie Cells ◽  
Evolutionarily Conserved ◽  
Hepatocyte Nuclear Factor 4Α ◽  
Hepatocyte Nuclear Factor 4Alpha

It has recently been shown that adenoviral-mediated expression of peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1 α) in hepatocytes stimulates glucose-6-phosphatase catalytic subunit (G6Pase) gene expression. A combination of fusion gene, gel retardation and chromatin immunoprecipitation assays revealed that, in H4IIE cells, PGC-1α mediates this stimulation through an evolutionarily conserved region of the G6Pase promoter that binds hepatocyte nuclear factor-4α.

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