-
Current Opinion in Plant Biology Dec 2017Each phosphoinositide (PI, also known as phosphatidylinositol phosphate, polyphosphoinositide, PtdInsP or PIP) species is partitioned in the endomembrane system and... (Review)
Review
Each phosphoinositide (PI, also known as phosphatidylinositol phosphate, polyphosphoinositide, PtdInsP or PIP) species is partitioned in the endomembrane system and thereby contributes to the identity of membrane compartments. However, membranes are in constant flux within this system, which raises the questions of how the spatiotemporal pattern of phosphoinositides is established and maintained within the cell. Here, we review the general mechanisms by which phosphoinositides and membrane trafficking feedbacks on each other to regulate cellular patterning. We then use the specific examples of polarized trafficking, endosomal sorting and vacuolar biogenesis to illustrate these general concepts.
Topics: Endosomes; Organelle Biogenesis; Phosphatidylinositols; Plants; Protein Transport; Vacuoles
PubMed: 28734137
DOI: 10.1016/j.pbi.2017.06.017 -
Journal of the American Society For... Nov 2000Structural characterization of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PI-4P), and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) by...
Characterization of phosphatidylinositol, phosphatidylinositol-4-phosphate, and phosphatidylinositol-4,5-bisphosphate by electrospray ionization tandem mass spectrometry: a mechanistic study.
Structural characterization of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PI-4P), and phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) by collisionally activated dissociation (CAD) tandem mass spectrometry with electrospray ionization is described. In negative ion mode, the major fragmentation pathways under low energy CAD for PI arise from neutral loss of free fatty acid substituents ([M - H - RxCO2H]-) and neutral loss of the corresponding ketenes ([M - H - R'xCH=C=O]-), followed by consecutive loss of the inositol head group. The intensities of the ions arising from neutral loss of the sn-2 substituent as a free fatty acid ([M - H - R2CO2H]-) or as a ketene ([M - H - R'2CH=C=O] ) are greater than those of ions reflecting corresponding losses of the sn-1 substutient. This is consistent with our recent finding that ions reflecting those losses arise from charge-driven processes that occur preferentially at the sn-2 position. These features permit assignment of the position of the fatty acid substituents on the glycerol backbone. Nucleophilic attack of the anionic phosphate onto the C-1 or the C-2 of the glycerol to which the fatty acids attached expels sn-1 (R1CO2-) or sn-2 (R2CO2-) carboxylate anion, respectively. This pathway is sterically more favorable at sn-2 than at sn-1. However, further dissociations of [M - H - RxCO2H - inositol] , [M - H - RxCO2H]-, and [M - H - RxCH=C=O]- precursor ions also yield RxCO2- ions, whose abundance are affected by the collision energy applied. Therefore, relative intensities of the RxCO2- ions in the spectrum do not reflect their positions on the glycerol backbone and determination of their regiospecificities based on their ion intensities is not reliable. The spectra also contain specific ions at m/z 315, 279, 259, 241, and 223, reflecting the inositol head group. The last three ions are also observed in the tandem spectra of the [M - H]- ions of phosphatidylinositol monophosphate (PI-P) and phosphatidylinositol bisphosphate (PI-P2), in addition to the ions at m/z 321 and 303, reflecting the doubly phosphorylated inositol ions. The PI-P2 also contains unique ions at m/z 401 and 383 that reflect the triply phosphorylated inositol ions. The [M - H]- ions of PI-P and PI-P2 undergo fragmentation pathways similar to that of PI upon CAD. However, the doubly charged ([M - 2H]2-) molecular ions undergo fragmentation pathways that are typical of the [M - H]- ions of glycerophosphoethanolamine, which are basic. These results suggest that the further deprotonated gaseous [M - 2H]2 ions of PI-P and PI-P2 are basic precursors.
Topics: Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Phosphatidylinositols; Spectrometry, Mass, Electrospray Ionization
PubMed: 11073262
DOI: 10.1016/S1044-0305(00)00172-0 -
Channels (Austin, Tex.) Dec 2020The Transient Receptor Potential Melastatin 8 (TRPM8) ion channel is an important sensor of environmental cold temperatures. Cold- and menthol-induced activation of this... (Review)
Review
The Transient Receptor Potential Melastatin 8 (TRPM8) ion channel is an important sensor of environmental cold temperatures. Cold- and menthol-induced activation of this channel requires the presence of the membrane phospholipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P]. This review discusses recent findings on the role of PI(4,5)P and G-proteins in the modulation of TRPM8 upon receptor activation. We will also summarize knowledge on the role of PI(4,5)P in Ca dependent desensitization/adaptation of TRPM8 activity, and recent advances in the structural basis of how this lipid binds to TRPM8.
Topics: Animals; Cold Temperature; Humans; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; TRPM Cation Channels; Transient Receptor Potential Channels
PubMed: 32101066
DOI: 10.1080/19336950.2020.1734266 -
The Journal of Physiology Sep 2010Phosphoinositides are a family of minority acidic phospholipids in cell membranes. Their principal role is instructional: they interact with proteins. Each cellular... (Review)
Review
Phosphoinositides are a family of minority acidic phospholipids in cell membranes. Their principal role is instructional: they interact with proteins. Each cellular membrane compartment uses a characteristic species of phosphoinositide. This signature phosphoinositide attracts a specific complement of functionally important, loosely attached peripheral proteins to that membrane. For example, the phosphatidylinositol 4,5-bisphosphate (PIP(2)) of the plasma membrane attracts phospholipase C, protein kinase C, proteins involved in membrane budding and fusion, proteins regulating the actin cytoskeleton, and others. Phosphoinositides also regulate the activity level of the integral membrane proteins. Many ion channels of the plasma membrane need the plasma-membrane-specific PIP(2) to function. Their activity decreases when the abundance of this lipid falls, as for example after activation of phospholipase C. This behaviour is illustrated by the suppression of KCNQ K(+) channel current by activation of M(1) muscarinic receptors; KCNQ channels require PIP(2) for their activity. In summary, phosphoinositides contribute to the selection of peripheral proteins for each membrane and regulate the activity of the integral proteins.
Topics: Animals; Humans; Membrane Lipids; Membrane Proteins; Phosphatidylinositols; Protein Transport
PubMed: 20519312
DOI: 10.1113/jphysiol.2010.192153 -
Biochimica Et Biophysica Acta Mar 2007It is now well appreciated that derivatives of phosphatidylinositol (PtdIns) are key regulators of many cellular processes in eukaryotes. Of particular interest are... (Review)
Review
It is now well appreciated that derivatives of phosphatidylinositol (PtdIns) are key regulators of many cellular processes in eukaryotes. Of particular interest are phosphoinositides (mono- and polyphosphorylated adducts to the inositol ring in PtdIns), which are located at the cytoplasmic face of cellular membranes. Phosphoinositides serve both a structural and a signaling role via their recruitment of proteins that contain phosphoinositide-binding domains. Phosphoinositides also have a role as precursors of several types of second messengers for certain intracellular signaling pathways. Realization of the importance of phosphoinositides has brought increased attention to characterization of the enzymes that regulate their synthesis, interconversion, and turnover. Here we review the current state of our knowledge about the properties and regulation of the ATP-dependent lipid kinases responsible for synthesis of phosphoinositides and also the additional temporal and spatial controls exerted by the phosphatases and a phospholipase that act on phosphoinositides in yeast.
Topics: 1-Phosphatidylinositol 4-Kinase; Animals; Humans; Phosphatidylinositol 3-Kinases; Phosphatidylinositols; Phosphoric Monoester Hydrolases; Phosphotransferases (Alcohol Group Acceptor); Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 17382260
DOI: 10.1016/j.bbalip.2007.01.015 -
Journal of Visualized Experiments : JoVE Jul 2017Numerous cellular proteins interact with membrane surfaces to affect essential cellular processes. These interactions can be directed towards a specific lipid component...
Numerous cellular proteins interact with membrane surfaces to affect essential cellular processes. These interactions can be directed towards a specific lipid component within a membrane, as in the case of phosphoinositides (PIPs), to ensure specific subcellular localization and/or activation. PIPs and cellular PIP-binding domains have been studied extensively to better understand their role in cellular physiology. We applied a pH modulation assay on supported lipid bilayers (SLBs) as a tool to study protein-PIP interactions. In these studies, pH sensitive ortho-Sulforhodamine B conjugated phosphatidylethanolamine is used to detect protein-PIP interactions. Upon binding of a protein to a PIP-containing membrane surface, the interfacial potential is modulated (i.e. change in local pH), shifting the protonation state of the probe. A case study of the successful usage of the pH modulation assay is presented by using phospholipase C delta1 Pleckstrin Homology (PLC-δ1 PH) domain and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) interaction as an example. The apparent dissociation constant (Kd,app) for this interaction was 0.39 ± 0.05 µM, similar to Kd,app values obtained by others. As previously observed, the PLC-δ1 PH domain is PI(4,5)P2 specific, shows weaker binding towards phosphatidylinositol 4-phosphate, and no binding to pure phosphatidylcholine SLBs. The PIP-on-a-chip assay is advantageous over traditional PIP-binding assays, including but not limited to low sample volume and no ligand/receptor labeling requirements, the ability to test high- and low-affinity membrane interactions with both small and large molecules, and improved signal to noise ratio. Accordingly, the usage of the PIP-on-a-chip approach will facilitate the elucidation of mechanisms of a wide range of membrane interactions. Furthermore, this method could potentially be used in identifying therapeutics that modulate protein's capacity to interact with membranes.
Topics: Humans; Hydrogen-Ion Concentration; Kinetics; Lipid Bilayers; Membrane Fluidity; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Phospholipase C delta; Protein Array Analysis; Protein Binding; Protein Domains; Unilamellar Liposomes; Video Recording
PubMed: 28784961
DOI: 10.3791/55869 -
Methods in Enzymology 2021Ion channel are embedded in the lipid bilayers of biological membranes. Membrane phospholipids constitute a barrier to ion movement, and they have been considered for a...
Ion channel are embedded in the lipid bilayers of biological membranes. Membrane phospholipids constitute a barrier to ion movement, and they have been considered for a long time as a passive environment for channel proteins. Membrane phospholipids, however, do not only serve as a passive amphipathic environment, but they also modulate channel activity by direct specific lipid-protein interactions. Phosphoinositides are quantitatively minor components of biological membranes, and they play roles in many cellular functions, including membrane traffic, cellular signaling and cytoskeletal organization. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P] is mainly found in the inner leaflet of the plasma membrane. Its role as a potential ion channel regulator was first appreciated over two decades ago and by now this lipid is a well-established cofactor or regulator of many different ion channels. The past two decades witnessed the steady development of techniques to study ion channel regulation by phosphoinositides with progress culminating in recent cryoEM structures that allowed visualization of how PI(4,5)P opens some ion channels. This chapter will provide an overview of the methods to study regulation by phosphoinositides, focusing on plasma membrane ion channels and PI(4,5)P.
Topics: Cell Membrane; Ion Channels; Lipid Bilayers; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols
PubMed: 34059290
DOI: 10.1016/bs.mie.2021.01.025 -
Communications Biology Apr 2023Synaptic plasticity involves proper establishment and rearrangement of structural and functional microdomains. Yet, visualization of the underlying lipid cues proved...
Synaptic plasticity involves proper establishment and rearrangement of structural and functional microdomains. Yet, visualization of the underlying lipid cues proved challenging. Applying a combination of rapid cryofixation, membrane freeze-fracturing, immunogold labeling and electron microscopy, we visualize and quantitatively determine the changes and the distribution of phosphatidylinositol-4,5-bisphosphate (PIP) in the plasma membrane of dendritic spines and subareas thereof at ultra-high resolution. These efforts unravel distinct phases of PIP signals during induction of long-term depression (LTD). During the first minutes PIP rapidly increases in a PIP5K-dependent manner forming nanoclusters. PTEN contributes to a second phase of PIP accumulation. The transiently increased PIP signals are restricted to upper and middle spine heads. Finally, PLC-dependent PIP degradation provides timely termination of PIP cues during LTD induction. Together, this work unravels the spatial and temporal cues set by PIP during different phases after LTD induction and dissects the molecular mechanisms underlying the observed PIP dynamics.
Topics: Neuronal Plasticity; Neurons; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Long-Term Synaptic Depression
PubMed: 37012315
DOI: 10.1038/s42003-023-04726-0 -
The FEBS Journal Dec 2013The last couple of decades have seen an extraordinary transformation in our knowledge and understanding of the multifarious biological roles of inositol phospholipids.... (Review)
Review
The last couple of decades have seen an extraordinary transformation in our knowledge and understanding of the multifarious biological roles of inositol phospholipids. Herein, I briefly consider two topics. The first is the role that recently acquired biochemical and genomic information - especially from archaeons - has played in illuminating the possible evolutionary origins of the biological employment of inositol in lipids, and some questions that these studies raise about the 'classical' biosynthetic route to phosphatidylinositol. The second is the growing recognition of the importance in eukaryotic cells of phosphatidylinositol 3,5-bisphosphate. Phosphatidylinositol 3,5-bisphosphate only entered our phosphoinositide consciousness quite recently, but it is speedily gathering a plethora of roles in diverse cellular processes and diseases thereof. These include: control of endolysosomal vesicular trafficking and of the activity of ion channels and pumps in the endolysosomal compartment; control of constitutive and stimulated protein traffic to and from plasma membrane subdomains; control of the nutrient and stress-sensing target of rapamycin complex 1 pathway (TORC1); and regulation of key genes in some central metabolic pathways.
Topics: Animals; Archaea; Disease; Humans; Phosphatidylinositol Phosphates; Phosphatidylinositols; Protein Transport
PubMed: 23902363
DOI: 10.1111/febs.12452 -
International Journal of Molecular... Mar 2022The activity of the epithelial Na Channel (ENaC) is strongly dependent on the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 binds two distinct...
The activity of the epithelial Na Channel (ENaC) is strongly dependent on the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2). PIP2 binds two distinct cationic clusters within the N termini of β- and γ-ENaC subunits (βN1 and γN2). The affinities of these sites were previously determined using short synthetic peptides, yet their role in sensitizing ENaC to changes in PIP2 levels in the cellular system is not well established. We addressed this question by comparing the effects of PIP2 depletion and recovery on ENaC channel activity and intracellular Na levels [Na]. We tested effects on ENaC activity with mutations to the PIP2 binding sites using the optogenetic system CIBN/CRY2-OCRL to selectively deplete PIP2. We monitored changes of [Na] by measuring the fluorescent Na indicator, CoroNa Green AM, and changes in channel activity by performing patch clamp electrophysiology. Whole cell patch clamp measurements showed a complete lack of response to PIP2 depletion and recovery in ENaC with mutations to βN1 or γN2 or both sites, compared to wild type ENaC. Whereas mutant βN1 also had no change in CoroNa Green fluorescence in response to PIP2 depletion, γN2 did have reduced [Na], which was explained by having shorter CoroNa Green uptake and half-life. These results suggest that CoroNa Green measurements should be interpreted with caution. Importantly, the electrophysiology results show that the βN1 and γN2 sites on ENaC are each necessary to permit maximal ENaC activity in the presence of PIP2.
Topics: Binding Sites; Epithelial Sodium Channels; Optogenetics; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Sodium
PubMed: 35409240
DOI: 10.3390/ijms23073884