Novel signalling mechanism and clinical applications of sperm-specific PLCζ

2015 ◽  
Vol 43 (3) ◽  
pp. 371-376 ◽  
Author(s):  
Michail Nomikos
Keyword(s):  
Embryonic Development ◽  
Mammalian Species ◽  
Specific Protein ◽  
Ph Domain ◽  
Substantial Evidence ◽  
Catalytic Domains ◽  
Protein Factor ◽  
Physiological Properties ◽  
Intracellular Vesicles ◽  
Ef Hands

Egg activation is the first step of embryonic development and in mammals is triggered by a series of cytoplasmic calcium (Ca2+) oscillations. Sperm–egg fusion initiates these Ca2+ oscillations by introducing a sperm-specific protein factor into the egg cytoplasm. Substantial evidence indicates that this protein is a sperm-specific phospholipase C (PLC), termed PLC-zeta (PLCζ). PLCζ stimulates cytoplasmic Ca2+ oscillations matching those at fertilization triggering early embryonic development in several mammalian species. Structurally, PLCζ is comprised of four EF-hands, a C2 domain, and X and Y catalytic domains. PLCζ is an unusual PLC since it lacks a pleckstrin homology (PH) domain. It is also distinctive in that its X–Y linker is not involved in auto-inhibition of catalytic activity, but instead binds to phosphatidylinositol 4,5-bisphosphate (PIP2). Moreover, relative to other PLC isoforms, PLCζ possesses unique potency in stimulating Ca2+ oscillations in eggs, although it does not appear to bind to plasma membrane PIP2. In contrast, PLCζ appears to interact with intracellular vesicles in eggs that contain PIP2. I discuss the recent advances in our knowledge of the intriguing biochemical and physiological properties of sperm PLCζ and postulate potential roles for PLCζ in terms of clinical diagnosis and therapy for certain forms of male infertility.

Extinction of phosphoenolpyruvate carboxykinase gene expression is associated with loss of a specific chromatin-binding protein from a far upstream domain

1990 ◽  
Vol 10 (7) ◽  
pp. 3782-3787
Author(s):  
Y T Ip ◽  
R E Fournier ◽  
R Chalkley
Keyword(s):  
Chromatin Structure ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Specific Protein ◽  
Gene Activity ◽  
Upstream Region ◽  
Hypersensitive Site ◽  
Chromosome 11 ◽  
Protein Factor ◽  
Hypersensitive Sites ◽  
Liver Gene

We have analyzed the chromatin structure of the phosphoenolpyruvate carboxykinase (PEPCK) gene in hepatoma x fibroblast hybrids with different extinction phenotypes. These hybrids included a karyotypically complete hybrid in which all liver gene activity was extinguished, a microcell hybrid that contained a single mouse chromosome 11 and in which PEPCK gene activity was decreased but inducible by cyclic AMP, and a segregant line that had lost all mouse chromosomes and in which the PEPCK gene was reexpressed. We found that only in the completely extinguished hybrid was PEPCK chromatin structure radically different from that in the parental hepatoma cells. In this hybrid, there was no evidence of any factors binding to the promoter or to the upstream hypersensitive site at -4800 base pairs. In the other cell lines, even when PEPCK gene transcription was low, the PEPCK chromatin showed characteristic structures typical of a transcriptionally competent gene, with hypersensitive sites at positions previously described. Loss of the upstream hypersensitive site was also shown to be correlated with the absence of a liver-specific protein factor that binds specifically to the upstream region.

scholarly journals Binding of Gd3+to the neuronal signalling protein calexcitin identifies an exchangeable Ca2+-binding site

2016 ◽  
Vol 72 (4) ◽  
pp. 276-281
Author(s):  
Lucas Chataigner ◽  
Jingxu Guo ◽  
Peter T. Erskine ◽  
Alun R. Coker ◽  
Steve P. Wood ◽  
...  
Keyword(s):  
Metal Ions ◽  
Binding Site ◽  
Metal Binding ◽  
Calcium Signalling ◽  
Specific Protein ◽  
Metal Binding Sites ◽  
Calcium Sensing ◽  
Neuronal Signalling ◽  
Ef Hand ◽  
Ef Hands

Calexcitin was first identified in the marine snailHermissenda crassicornisas a neuronal-specific protein that becomes upregulated and phosphorylated in associative learning. Calexcitin possesses four EF-hand motifs, but only the first three (EF-1 to EF-3) are involved in binding metal ions. Past work has indicated that under physiological conditions EF-1 and EF-2 bind Mg2+and Ca2+, while EF-3 is likely to bind only Ca2+. The fourth EF-hand is nonfunctional owing to a lack of key metal-binding residues. The aim of this study was to use a crystallographic approach to determine which of the three metal-binding sites of calexcitin is most readily replaced by exogenous metal ions, potentially shedding light on which of the EF-hands play a `sensory' role in neuronal calcium signalling. By co-crystallizing recombinant calexcitin with equimolar Gd3+in the presence of trace Ca2+, EF-1 was shown to become fully occupied by Gd3+ions, while the other two sites remain fully occupied by Ca2+. The structure of the Gd3+–calexcitin complex has been refined to anRfactor of 21.5% and anRfreeof 30.4% at 2.2 Å resolution. These findings suggest that EF-1 of calexcitin is the Ca2+-binding site with the lowest selectivity for Ca2+, and the implications of this finding for calcium sensing in neuronal signalling pathways are discussed.

Intrinsic physiological properties of rat retinal ganglion cells with a comparative analysis

2012 ◽  
Vol 108 (7) ◽  
pp. 2008-2023 ◽  
Author(s):  
Raymond C. S. Wong ◽  
Shaun L. Cloherty ◽  
Michael R. Ibbotson ◽  
Brendan J. O'Brien
Keyword(s):  
Ganglion Cells ◽  
Mammalian Species ◽  
Cell Types ◽  
Retinal Ganglion ◽  
Intrinsic Properties ◽  
Cat Retina ◽  
Physiological Properties ◽  
Behavioral Needs ◽  
Mammalian Retina ◽  
Do So

Mammalian retina contains 15–20 different retinal ganglion cell (RGC) types, each of which is responsible for encoding different aspects of the visual scene. The encoding is defined by a combination of RGC synaptic inputs, the neurotransmitter systems used, and their intrinsic physiological properties. Each cell's intrinsic properties are defined by its morphology and membrane characteristics, including the complement and localization of the ion channels expressed. In this study, we examined the hypothesis that the intrinsic properties of individual RGC types are conserved among mammalian species. To do so, we measured the intrinsic properties of 16 morphologically defined rat RGC types and compared these data with cat RGC types. Our data demonstrate that in the rat different morphologically defined RGC types have distinct patterns of intrinsic properties. Variation in these properties across cell types was comparable to that found for cat RGC types. When presumed morphological homologs in rat and cat retina were compared directly, some RGC types had very similar properties. The rat A2 cell exhibited patterns of intrinsic properties nearly identical to the cat alpha cell. In contrast, rat D2 cells (ON-OFF directionally selective) had a very different pattern of intrinsic properties than the cat iota cell. Our data suggest that the intrinsic properties of RGCs with similar morphology and suspected visual function may be subject to variation due to the behavioral needs of the species.

scholarly journals Proximal Protein Interaction Landscape of RAS Paralogs

Cancers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3326 ◽  
Author(s):  
Benoît Béganton ◽  
Etienne Coyaud ◽  
Estelle M. N. Laurent ◽  
Alain Mangé ◽  
Julien Jacquemetton ◽  
...  
Keyword(s):  
Protein Interaction ◽  
Protein Interactions ◽  
Biological Activities ◽  
Mammalian Species ◽  
Variable Region ◽  
Specific Protein ◽  
Protein Networks ◽  
Ras Proteins ◽  
Wild Type ◽  
Protein Protein Interaction

RAS proteins (KRAS, NRAS and HRAS) are frequently activated in different cancer types (e.g., non-small cell lung cancer, colorectal cancer, melanoma and bladder cancer). For many years, their activities were considered redundant due to their high degree of sequence homology (80% identity) and their shared upstream and downstream protein partners. However, the high conservation of the Hyper-Variable-Region across mammalian species, the preferential activation of different RAS proteins in specific tumor types and the specific post-translational modifications and plasma membrane-localization of each paralog suggest they could ensure discrete functions. To gain insights into RAS proteins specificities, we explored their proximal protein–protein interaction landscapes using the proximity-dependent biotin identification technology (BioID) in Flp-In T-REx 293 cell lines stably transfected and inducibly expressing wild type KRAS4B, NRAS or HRAS. We identified more than 800 high-confidence proximal interactors, allowing us to propose an unprecedented comparative analysis of wild type RAS paralogs protein networks. These data bring novel information on poorly characterized RAS functions, e.g., its putative involvement in metabolic pathways, and on shared as well as paralog-specific protein networks that could partially explain the complexity of RAS functions. These networks of protein interactions open numerous avenues to better understand RAS paralogs biological activities.

scholarly journals Functional and structural characterization of allosteric activation of phospholipase Cε by Rap1A

2020 ◽  
Vol 295 (49) ◽  
pp. 16562-16571
Author(s):  
Monita Sieng ◽  
Arielle F. Selvia ◽  
Elisabeth E. Garland-Kuntz ◽  
Jesse B. Hopkins ◽  
Isaac J. Fisher ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Small Gtpases ◽  
Ph Domain ◽  
Hydrophobic Residues ◽  
X Ray Scattering ◽  
Catalytically Active ◽  
Ef Hands ◽  
Β Adrenergic Receptors ◽  
G Protein Coupled ◽  
Phospholipase Cε

Phospholipase Cε (PLCε) is activated downstream of G protein–coupled receptors and receptor tyrosine kinases through direct interactions with small GTPases, including Rap1A and Ras. Although Ras has been reported to allosterically activate the lipase, it is not known whether Rap1A has the same ability or what its molecular mechanism might be. Rap1A activates PLCε in response to the stimulation of β-adrenergic receptors, translocating the complex to the perinuclear membrane. Because the C-terminal Ras association (RA2) domain of PLCε was proposed to the primary binding site for Rap1A, we first confirmed using purified proteins that the RA2 domain is indeed essential for activation by Rap1A. However, we also showed that the PLCε pleckstrin homology (PH) domain and first two EF hands (EF1/2) are required for Rap1A activation and identified hydrophobic residues on the surface of the RA2 domain that are also necessary. Small-angle X-ray scattering showed that Rap1A binding induces and stabilizes discrete conformational states in PLCε variants that can be activated by the GTPase. These data, together with the recent structure of a catalytically active fragment of PLCε, provide the first evidence that Rap1A, and by extension Ras, allosterically activate the lipase by promoting and stabilizing interactions between the RA2 domain and the PLCε core.

scholarly journals Extinction of phosphoenolpyruvate carboxykinase gene expression is associated with loss of a specific chromatin-binding protein from a far upstream domain.

1990 ◽  
Vol 10 (7) ◽  
pp. 3782-3787 ◽  
Author(s):  
Y T Ip ◽  
R E Fournier ◽  
R Chalkley
Keyword(s):  
Chromatin Structure ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Specific Protein ◽  
Gene Activity ◽  
Upstream Region ◽  
Hypersensitive Site ◽  
Chromosome 11 ◽  
Protein Factor ◽  
Hypersensitive Sites ◽  
Liver Gene

We have analyzed the chromatin structure of the phosphoenolpyruvate carboxykinase (PEPCK) gene in hepatoma x fibroblast hybrids with different extinction phenotypes. These hybrids included a karyotypically complete hybrid in which all liver gene activity was extinguished, a microcell hybrid that contained a single mouse chromosome 11 and in which PEPCK gene activity was decreased but inducible by cyclic AMP, and a segregant line that had lost all mouse chromosomes and in which the PEPCK gene was reexpressed. We found that only in the completely extinguished hybrid was PEPCK chromatin structure radically different from that in the parental hepatoma cells. In this hybrid, there was no evidence of any factors binding to the promoter or to the upstream hypersensitive site at -4800 base pairs. In the other cell lines, even when PEPCK gene transcription was low, the PEPCK chromatin showed characteristic structures typical of a transcriptionally competent gene, with hypersensitive sites at positions previously described. Loss of the upstream hypersensitive site was also shown to be correlated with the absence of a liver-specific protein factor that binds specifically to the upstream region.

Dynamic expression of the vertebrate-specific protein Nucks during rodent embryonic development

2014 ◽  
Vol 14 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Yiannis Drosos ◽  
Mirsini Kouloukoussa ◽  
Anne Carine Østvold ◽  
Sophia Havaki ◽  
Eleni Katsantoni ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Specific Protein ◽  
Dynamic Expression
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