PIP2
Dotaz
Zobrazit nápovědu
One of the most studied phosphoinositides is phosphatidylinositol 4,5-bisphosphate (PIP2), which localizes to the plasma membrane, nuclear speckles, small foci in the nucleoplasm, and to the nucleolus in mammalian cells. Here, we show that PIP2 also localizes to the nucleus in prophase I, during the gametogenesis of C. elegans hermaphrodite. The depletion of PIP2 by type I PIP kinase (PPK-1) kinase RNA interference results in an altered chromosome structure and leads to various defects during meiotic progression. We observed a decreased brood size and aneuploidy in progeny, defects in synapsis, and crossover formation. The altered chromosome structure is reflected in the increased transcription activity of a tightly regulated process in prophase I. To elucidate the involvement of PIP2 in the processes during the C. elegans development, we identified the PIP2-binding partners, leucine-rich repeat (LRR-1) protein and proteasome subunit beta 4 (PBS-4), pointing to its involvement in the ubiquitin⁻proteasome pathway.
- MeSH
- buněčné jádro metabolismus MeSH
- Caenorhabditis elegans genetika růst a vývoj metabolismus MeSH
- chromozomy chemie MeSH
- fosfatidylinositol-4,5-difosfát metabolismus MeSH
- fosfotransferasy s alkoholovou skupinou jako akceptorem genetika MeSH
- gametogeneze * MeSH
- hermafroditické organismy genetika růst a vývoj metabolismus MeSH
- profáze meiózy I MeSH
- proteasomový endopeptidasový komplex metabolismus MeSH
- proteiny Caenorhabditis elegans genetika MeSH
- proteiny metabolismus MeSH
- RNA interference MeSH
- vývojová regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Phosphoinositides are present in the plasma membrane, cytoplasm and inside the cell nucleus. Here we identify phosphatidylinositol-4,5-bisphosphate (PIP2) as a regulator of rRNA genes transcription at the epigenetic level. We show that PIP2 directly interacts with histone lysine demethylase PHF8 (PHD finger protein 8) and represses demethylation of H3K9me2 through this interaction. We identify the C-terminal K/R-rich motif as PIP2-binding site within PHF8, and address the function of this PIP2-PHF8 complex. PIP2-binding mutant of PHF8 has increased the activity of rDNA promoter (20%) and expression of pre-rRNA genes (47S-100%; 45S-66%). Furthermore, trypsin digestion reveals a potential conformational change of PHF8 upon PIP2 binding. These observations identify the function of nuclear PIP2, and suggest that PIP2 contributes to the fine-tuning of rDNA transcription.
- MeSH
- epigeneze genetická * MeSH
- fosfatidylinositol-4,5-difosfát genetika metabolismus MeSH
- genetická transkripce * MeSH
- geny rRNA * MeSH
- HEK293 buňky MeSH
- HeLa buňky MeSH
- histondemethylasy genetika metabolismus MeSH
- lidé MeSH
- mutace MeSH
- promotorové oblasti (genetika) * MeSH
- RNA ribozomální biosyntéza genetika MeSH
- transkripční faktory genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The transient receptor potential melastatin 4 (TRPM4) is a calcium-activated non-selective ion channel broadly expressed in a variety of tissues. Receptor has been identified as a crucial modulator of numerous calcium dependent mechanisms in the cell such as immune response, cardiac conduction, neurotransmission and insulin secretion. It is known that phosphoinositide lipids (PIPs) play a unique role in the regulation of TRP channel function. However the molecular mechanism of this process is still unknown. We characterized the binding site of PIP2 and its structural analogue PIP3 in the E733-W772 proximal region of the TRPM4 N-terminus via biophysical and molecular modeling methods. The specific positions R755 and R767 in this domain were identified as being important for interactions with PIP2/PIP3 ligands. Their mutations caused a partial loss of PIP2/PIP3 binding specificity. The interaction of PIP3 with TRPM4 channels has never been described before. These findings provide new insight into the ligand binding domains of the TRPM4 channel.
- MeSH
- dimyristoylfosfatidylcholin analogy a deriváty metabolismus MeSH
- fosfatidylinositol-4,5-difosfát metabolismus MeSH
- kationtové kanály TRPM chemie metabolismus MeSH
- lidé MeSH
- molekulární sekvence - údaje MeSH
- peptidové fragmenty chemie metabolismus MeSH
- sekundární struktura proteinů MeSH
- sekvence aminokyselin MeSH
- simulace molekulového dockingu MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Transient receptor potential melastatin-1 (TRPM1) is a calcium channel that is essential for the depolarization of photo-responsive retinal bipolar cells, but most of the physiological functions and cellular roles of this channel are still poorly understood. Most transient receptor potential (TRP) channels are typically regulated by intracellular proteins and other signaling molecules. Phosphatidylinositol-4,5 bisphosphate (PIP2), a minor phospholipid component of cell membranes, has previously been shown to directly bind TRP channels and to play a unique role in modulating receptor function. To characterize the binding of PIP2 as a potential regulator of TRPM1, we utilized biophysical methods and molecular modeling to study the interactions of PIP2 with an N-terminal fragment of TRPM1 (residues A451-N566). The basic N-terminal residue K464 of TRPM1 suggests that it is part of putative pleckstrin homology (PH) domain and is involved in the interactions with PIP2. This is the first report detailing the binding of PIP2 at the N-terminus of the TRPM1 receptor.
- MeSH
- cirkulární dichroismus MeSH
- fosfatidylinositol-4,5-difosfát chemie metabolismus MeSH
- kationtové kanály TRPM chemie genetika metabolismus MeSH
- lidé MeSH
- povrchová plasmonová rezonance MeSH
- rekombinantní proteiny biosyntéza chemie izolace a purifikace MeSH
- sekundární struktura proteinů MeSH
- simulace molekulární dynamiky MeSH
- terciární struktura proteinů MeSH
- vazba proteinů MeSH
- vazebná místa MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Molecular determinants of the binding of various endogenous modulators to transient receptor potential (TRP) channels are crucial for the understanding of necessary cellular pathways, as well as new paths for rational drug designs. The aim of this study was to characterise interactions between the TRP cation channel subfamily melastatin member 4 (TRPM4) and endogenous intracellular modulators-calcium-binding proteins (calmodulin (CaM) and S100A1) and phosphatidylinositol 4, 5-bisphosphate (PIP2). We have found binding epitopes at the N- and C-termini of TRPM4 shared by CaM, S100A1 and PIP2. The binding affinities of short peptides representing the binding epitopes of N- and C-termini were measured by means of fluorescence anisotropy (FA). The importance of representative basic amino acids and their combinations from both peptides for the binding of endogenous TRPM4 modulators was proved using point alanine-scanning mutagenesis. In silico protein-protein docking of both peptides to CaM and S100A1 and extensive molecular dynamics (MD) simulations enabled the description of key stabilising interactions at the atomic level. Recently solved cryo-Electron Microscopy (EM) structures made it possible to put our findings into the context of the entire TRPM4 channel and to deduce how the binding of these endogenous modulators could allosterically affect the gating of TRPM4. Moreover, both identified binding epitopes seem to be ideally positioned to mediate the involvement of TRPM4 in higher-order hetero-multimeric complexes with important physiological functions.
- MeSH
- akvaporiny chemie metabolismus MeSH
- interakční proteinové domény a motivy * MeSH
- kalmodulin chemie metabolismus MeSH
- kationtové kanály TRPM chemie metabolismus MeSH
- kinetika MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární modely MeSH
- multiproteinové komplexy chemie metabolismus MeSH
- peptidové fragmenty MeSH
- proteiny S100 chemie metabolismus MeSH
- sekvence aminokyselin MeSH
- vazba proteinů MeSH
- vazebná místa * MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Capsaicin and other vanilloids selectively excite and subsequently desensitize pain-conducting nerve fibers (nociceptors) and this process contributes to the analgesic (and thus therapeutically relevant) effects of these compounds. Such a desensitization process is triggered by the activation of the transient receptor potential vanilloid subtype 1 receptor channels (TRPV1) that open their cationic pores, permeable to sodium, potassium and calcium (Ca(2+)) ions. Depending on the duration of capsaicin exposure and the external calcium concentration, the Ca(2+) influx via TRPV1 channels desensitizes the channels themselves, which, from the cellular point of view, represents a feedback mechanism protecting the nociceptive neuron from toxic Ca(2+) overload. The 'acute desensitization' accounts for most of the reduction in responsiveness occurring within the first few (~20) seconds after the vanilloids are administered to the cell for the first time. Another form of desensitization is 'tachyphylaxis', which is a reduction in the response to repeated applications of vanilloid. The wealth of pathways following TRPV1 activation that lead to increased intracellular Ca(2+) levels and both forms of desensitization is huge and they might utilise just about every known type of signalling molecule. This review will not attempt to cover all historical aspects of research into all these processes. Instead, it will try to highlight some new challenging thoughts on the important phenomenon of TRPV1 desensitization and will focus on the putative mechanisms that are thought to account for the acute phase of this process.
- MeSH
- analgetika metabolismus farmakologie MeSH
- fosfolipasa C fosfoinositidové signalizace metabolismus MeSH
- fosforylace MeSH
- kapsaicin metabolismus farmakologie MeSH
- kationtové kanály TRPV agonisté metabolismus MeSH
- lidé MeSH
- nociceptory metabolismus MeSH
- vápník metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
Mutations of the TMPRSS6 gene, encoding the serine protease matriptase-2, lead to iron-refractory iron deficiency anemia. Matriptase-2 is a potent negative regulator of hepcidin. Based on in vitro data, it has recently been proposed that matriptase-2 decreases hepcidin synthesis by cleaving membrane hemojuvelin, a key protein of the hepcidin-regulatory pathway. However, in vivo evidence for this mechanism of action of matriptase-2 is lacking. To investigate the hemojuvelin-matriptase-2 interaction in vivo, an immunoblot assay for liver membrane hemojuvelin was optimized using hemojuvelin-mutant mice as a negative control. In wild-type mice, two hemojuvelin-specific bands of 35kDa and 20kDa were detected in mouse liver membrane fraction under reducing conditions; under non-reducing conditions, a single band of approximately 50kDa was seen. Phosphatidylinositol-specific phospholipase C treatment confirmed binding of the detected protein to the cell membrane by a glycosylphosphatidylinositol anchor, indicating that the major form of mouse liver membrane hemojuvelin is a glycosylphosphatidylinositol-bound heterodimer. Unexpectedly, comparison of liver homogenates from Tmprss6+/+ and Tmprss6-/- mice revealed significantly decreased, rather than increased, hemojuvelin heterodimer content in Tmprss6-/- mice. These data do not provide direct support for the concept that matriptase-2 cleaves membrane hemojuvelin and may indicate that, in vivo, the role of matriptase-2 in the regulation of hepcidin gene expression is more complex.
- MeSH
- anemie z nedostatku železa genetika metabolismus MeSH
- buněčná membrána genetika metabolismus MeSH
- dimerizace MeSH
- elektroforéza v polyakrylamidovém gelu MeSH
- fosfolipasa C fosfoinositidové signalizace metabolismus MeSH
- glykosylfosfatidylinositoly chemie metabolismus MeSH
- játra metabolismus patologie MeSH
- kationické antimikrobiální peptidy genetika metabolismus MeSH
- membránové proteiny nedostatek genetika metabolismus MeSH
- myši knockoutované MeSH
- myši MeSH
- polymerázová řetězová reakce MeSH
- regulace genové exprese MeSH
- serinové endopeptidasy nedostatek genetika MeSH
- signální transdukce genetika MeSH
- tkáňové extrakty chemie MeSH
- železo metabolismus MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
RNA polymerase I (Pol I) transcription is essential for the cell cycle, growth and protein synthesis in eukaryotes. In the present study, we found that phosphatidylinositol 4,5-bisphosphate (PIP2) is a part of the protein complex on the active ribosomal promoter during transcription. PIP2 makes a complex with Pol I and the Pol I transcription factor UBF in the nucleolus. PIP2 depletion reduces Pol I transcription, which can be rescued by the addition of exogenous PIP2. In addition, PIP2 also binds directly to the pre-rRNA processing factor fibrillarin (Fib), and co-localizes with nascent transcripts in the nucleolus. PIP2 binding to UBF and Fib modulates their binding to DNA and RNA, respectively. In conclusion, PIP2 interacts with a subset of Pol I transcription machinery, and promotes Pol I transcription.
- MeSH
- buněčné jadérko genetika metabolismus MeSH
- chromozomální proteiny, nehistonové genetika metabolismus MeSH
- DNA vazebné proteiny genetika metabolismus MeSH
- fosfatidylinositol-4,5-difosfát genetika metabolismus MeSH
- genetická transkripce genetika MeSH
- HeLa buňky MeSH
- lidé MeSH
- nádorové buněčné linie MeSH
- prekurzory RNA genetika metabolismus MeSH
- promotorové oblasti (genetika) genetika MeSH
- RNA-polymerasa I genetika metabolismus MeSH
- transkripční iniciační komplex Pol1 - proteiny genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
