-
The Journal of Cell Biology Aug 2023The maintenance of plasma membrane integrity and a capacity for efficiently repairing damaged membranes are essential for cell survival. Large-scale wounding depletes...
The maintenance of plasma membrane integrity and a capacity for efficiently repairing damaged membranes are essential for cell survival. Large-scale wounding depletes various membrane components at the wound sites, including phosphatidylinositols, yet little is known about how phosphatidylinositols are generated after depletion. Here, working with our in vivo C. elegans epidermal cell wounding model, we discovered phosphatidylinositol 4-phosphate (PtdIns4P) accumulation and local phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] generation at the wound site. We found that PtdIns(4,5)P2 generation depends on the delivery of PtdIns4P, PI4K, and PI4P 5-kinase PPK-1. In addition, we show that wounding triggers enrichment of the Golgi membrane to the wound site, and that is required for membrane repair. Moreover, genetic and pharmacological inhibitor experiments support that the Golgi membrane provides the PtdIns4P for PtdIns(4,5)P2 generation at the wounds. Our findings demonstrate how the Golgi apparatus facilitates membrane repair in response to wounding and offers a valuable perspective on cellular survival mechanisms upon mechanical stress in a physiological context.
Topics: Animals; Caenorhabditis elegans; Cell Membrane; Golgi Apparatus; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Stress, Mechanical
PubMed: 37158801
DOI: 10.1083/jcb.202303017 -
Developmental Cell Jul 2022Focal adhesions are multifunctional organelles that couple cell-matrix adhesion to cytoskeletal force transmission and signaling and to steer cell migration and...
Focal adhesions are multifunctional organelles that couple cell-matrix adhesion to cytoskeletal force transmission and signaling and to steer cell migration and collective cell behavior. Whereas proteomic changes at focal adhesions are well understood, little is known about signaling lipids in focal adhesion dynamics. Through the characterization of cells from mice with a kinase-inactivating point mutation in the class II PI3K-C2β, we find that generation of the phosphatidylinositol-3,4-bisphosphate (PtdIns(3,4)P) membrane lipid promotes focal adhesion disassembly in response to changing environmental conditions. We show that reduced growth factor signaling sensed by protein kinase N, an mTORC2 target and effector of RhoA, synergizes with the adhesion disassembly factor DEPDC1B to induce local synthesis of PtdIns(3,4)P by PI3K-C2β. PtdIns(3,4)P then promotes turnover of RhoA-dependent stress fibers by recruiting the PtdIns(3,4)P-dependent RhoA-GTPase-activating protein ARAP3. Our findings uncover a pathway by which cessation of growth factor signaling facilitates cell-matrix adhesion disassembly via a phosphoinositide lipid switch.
Topics: Animals; Cell Adhesion; Focal Adhesions; Mice; Phosphatidylinositol 3-Kinases; Phosphatidylinositol Phosphates; Phosphatidylinositols; Proteomics
PubMed: 35809565
DOI: 10.1016/j.devcel.2022.06.011 -
Traffic (Copenhagen, Denmark) Apr 2003Domains or modules known to bind phosphoinositides have increased dramatically in number over the past few years, and are found in proteins involved in intracellular... (Review)
Review
Domains or modules known to bind phosphoinositides have increased dramatically in number over the past few years, and are found in proteins involved in intracellular trafficking, cellular signaling, and cytoskeletal remodeling. Analysis of lipid binding by these domains and its structural basis has provided significant insight into the mechanism of membrane recruitment by the different cellular phosphoinositides. Domains that target only the rare (3-phosphorylated) phosphoinositides must bind with very high affinity, and with exquisite specificity. This is achieved solely by headgroup interactions in the case of certain pleckstrin homology (PH) domains [which bind PtdIns(3,4,5)P3 and/or PtdIns(3,4)P2], but requires an additional membrane-insertion and/or oligomerization component in the case of the PtdIns(3)P-targeting phox homology (PX) and FYVE domains. Domains that target PtdIns(4,5)P2, which is more abundant by some 25-fold, do not require the same stringent affinity and specificity characteristics, and tend to be more diverse in structure. The mode of phosphoinositide binding by different domains also appears to reflect their distinct functions. For example, pleckstrin homology domains that serve as simple targeting domains recognize only phosphoinositide headgroups. By contrast, certain other domains, notably the epsin ENTH domain, appear to promote bilayer curvature by inserting into the membrane upon binding.
Topics: Binding Sites; Models, Molecular; Phosphatidylinositols; Second Messenger Systems; Signal Transduction
PubMed: 12694559
DOI: 10.1034/j.1600-0854.2004.00071.x -
Biochimica Et Biophysica Acta Jun 2015Phosphoinositides (PIs) are minor components of cell membranes, but play key roles in cell function. Recent refinements in techniques for their detection, together with... (Review)
Review
Phosphoinositides (PIs) are minor components of cell membranes, but play key roles in cell function. Recent refinements in techniques for their detection, together with imaging methods to study their distribution and changes, have greatly facilitated the study of these lipids. Such methods have been complemented by the parallel development of techniques for the acute manipulation of their levels, which in turn allow bypassing the long-term adaptive changes implicit in genetic perturbations. Collectively, these advancements have helped elucidate the role of PIs in physiology and the impact of the dysfunction of their metabolism in disease. Combining methods for detection and manipulation enables the identification of specific roles played by each of the PIs and may eventually lead to the complete deconstruction of the PI signaling network. Here, we review current techniques used for the study and manipulation of cellular PIs and also discuss advantages and disadvantages associated with the various methods. This article is part of a Special Issue entitled Phosphoinositides.
Topics: Antibodies; Cell Membrane; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Enzyme Inhibitors; Fluorescence Resonance Energy Transfer; Gene Targeting; Humans; Microscopy; Optogenetics; Phosphatidylinositols; Phosphotransferases (Alcohol Group Acceptor); Protein Structure, Tertiary; Signal Transduction
PubMed: 25514766
DOI: 10.1016/j.bbalip.2014.12.008 -
The Journal of Biological Chemistry 2021Ceramide-1-phosphate transfer proteins (CPTPs) are members of the glycolipid transfer protein (GLTP) superfamily that shuttle ceramide-1-phosphate (C1P) between...
Ceramide-1-phosphate transfer proteins (CPTPs) are members of the glycolipid transfer protein (GLTP) superfamily that shuttle ceramide-1-phosphate (C1P) between membranes. CPTPs regulate cellular sphingolipid homeostasis in ways that impact programmed cell death and inflammation. CPTP downregulation specifically alters C1P levels in the plasma and trans-Golgi membranes, stimulating proinflammatory eicosanoid production and autophagy-dependent inflammasome-mediated cytokine release. However, the mechanisms used by CPTP to target the trans-Golgi and plasma membrane are not well understood. Here, we monitored C1P intervesicular transfer using fluorescence energy transfer (FRET) and showed that certain phosphoinositides (phosphatidylinositol 4,5 bisphosphate (PI-(4,5)P) and phosphatidylinositol 4-phosphate (PI-4P)) increased CPTP transfer activity, whereas others (phosphatidylinositol 3-phosphate (PI-3P) and PI) did not. PIPs that stimulated CPTP did not stimulate GLTP, another superfamily member. Short-chain PI-(4,5)P which is soluble and does not remain membrane-embedded, failed to activate CPTP. CPTP stimulation by physiologically relevant PI-(4,5)P levels surpassed that of phosphatidylserine (PS), the only known non-PIP stimulator of CPTP, despite PI-(4,5)P increasing membrane equilibrium binding affinity less effectively than PS. Functional mapping of mutations that led to altered FRET lipid transfer and assessment of CPTP membrane interaction by surface plasmon resonance indicated that di-arginine motifs located in the α-6 helix and the α3-α4 helix regulatory loop of the membrane-interaction region serve as PI-(4,5)P headgroup-specific interaction sites. Haddock modeling revealed specific interactions involving the PI-(4,5)P headgroup that left the acyl chains oriented favorably for membrane embedding. We propose that PI-(4,5)P interaction sites enhance CPTP activity by serving as preferred membrane targeting/docking sites that favorably orient the protein for function.
Topics: Homeostasis; Humans; Models, Molecular; Phosphatidylinositols; Phospholipid Transfer Proteins; Protein Conformation, alpha-Helical
PubMed: 33781749
DOI: 10.1016/j.jbc.2021.100600 -
Annual Review of Physiology Feb 2024Transient receptor potential (TRP) ion channels have diverse activation mechanisms including physical stimuli, such as high or low temperatures, and a variety of... (Review)
Review
Transient receptor potential (TRP) ion channels have diverse activation mechanisms including physical stimuli, such as high or low temperatures, and a variety of intracellular signaling molecules. Regulation by phosphoinositides and their derivatives is their only known common regulatory feature. For most TRP channels, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P] serves as a cofactor required for activity. Such dependence on PI(4,5)P has been demonstrated for members of the TRPM subfamily and for the epithelial TRPV5 and TRPV6 channels. Intracellular TRPML channels show specific activation by PI(3,5)P. Structural studies uncovered the PI(4,5)P and PI(3,5)P binding sites for these channels and shed light on the mechanism of channel opening. PI(4,5)P regulation of TRPV1-4 as well as some TRPC channels is more complex, involving both positive and negative effects. This review discusses the functional roles of phosphoinositides in TRP channel regulation and molecular insights gained from recent cryo-electron microscopy structures.
Topics: Humans; Transient Receptor Potential Channels; Phosphatidylinositols; Cryoelectron Microscopy
PubMed: 37871124
DOI: 10.1146/annurev-physiol-042022-013956 -
Journal of Cell Science Nov 2015Phosphoinositides are a collection of lipid messengers that regulate most subcellular processes. Amongst the seven phosphoinositide species, the roles for... (Review)
Review
Phosphoinositides are a collection of lipid messengers that regulate most subcellular processes. Amongst the seven phosphoinositide species, the roles for phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] at the plasma membrane, such as in endocytosis, exocytosis, actin polymerization and focal adhesion assembly, have been extensively studied. Recent studies have argued for the existence of PtdIns(4,5)P2 at multiple intracellular compartments, including the nucleus, endosomes, lysosomes, autolysosomes, autophagic precursor membranes, ER, mitochondria and the Golgi complex. Although the generation, regulation and functions of PtdIns(4,5)P2 are less well-defined in most other intracellular compartments, accumulating evidence demonstrates crucial roles for PtdIns(4,5)P2 in endolysosomal trafficking, endosomal recycling, as well as autophagosomal pathways, which are the focus of this Commentary. We summarize and discuss how phosphatidylinositol phosphate kinases, PtdIns(4,5)P2 and PtdIns(4,5)P2-effectors regulate these intracellular protein and membrane trafficking events.
Topics: Animals; Cell Membrane; Humans; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Signal Transduction
PubMed: 26574506
DOI: 10.1242/jcs.175208 -
Pflugers Archiv : European Journal of... Sep 2015The heat- and capsaicin-sensitive transient receptor potential vanilloid 1 ion channel (TRPV1) is regulated by plasma membrane phosphoinositides. The effects of these... (Review)
Review
The heat- and capsaicin-sensitive transient receptor potential vanilloid 1 ion channel (TRPV1) is regulated by plasma membrane phosphoinositides. The effects of these lipids on this channel have been controversial. Recent articles re-ignited the debate and also offered resolution to place some of the data in a coherent picture. This review summarizes the literature on this topic and provides a detailed and critical discussion on the experimental evidence for the various effects of phosphatidylinositol 4,5-bisphosphayte [PI(4,5)P2 or PIP2] on TRPV1. We conclude that PI(4,5)P2 and potentially its precursor PI(4)P are positive cofactors for TRPV1, acting via direct interaction with the channel, and their depletion by Ca(2+)-induced activation of phospholipase Cδ isoforms (PLCδ) limits channel activity during capsaicin-induced desensitization. Other negatively charged lipids at higher concentrations can also support channel activity, which may explain some controversies in the literature. PI(4,5)P2 also partially inhibits channel activity in some experimental settings, and relief from this inhibition upon PLCβ activation may contribute to sensitization. The negative effect of PI(4,5)P2 is more controversial and its mechanism is less well understood. Other TRP channels from the TRPV and TRPC families may also undergo similar dual regulation by phosphoinositides, thus the complexity of TRPV1 regulation is not unique to this channel.
Topics: Animals; Humans; Phosphatidylinositols; TRPV Cation Channels
PubMed: 25754030
DOI: 10.1007/s00424-015-1695-3 -
Journal of Biochemistry Oct 2020Inositol phospholipids are low-abundance regulatory lipids that orchestrate diverse cellular functions in eukaryotic organisms. Recent studies have uncovered involvement... (Review)
Review
Inositol phospholipids are low-abundance regulatory lipids that orchestrate diverse cellular functions in eukaryotic organisms. Recent studies have uncovered involvement of the lipids in multiple steps in autophagy. The late endosome-lysosome compartment plays critical roles in cellular nutrient sensing and in the control of both the initiation of autophagy and the late stage of eventual degradation of cytosolic materials destined for elimination. It is particularly notable that inositol lipids are involved in almost all steps of the autophagic process. In this review, we summarize how inositol lipids regulate and contribute to autophagy through the endomembrane compartments, primarily focusing on PI4P and PI(4,5)P2.
Topics: Animals; Autophagy; Endosomes; Humans; Lysosomes; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Phosphatidylinositols; Signal Transduction
PubMed: 32745205
DOI: 10.1093/jb/mvaa089 -
Current Topics in Microbiology and... 2010The phosphoinositide-3-kinase (PI3K) family of lipid kinases has been well conserved from yeast to mammals. In this evolutionary perspective on the PI3K family, we...
The phosphoinositide-3-kinase (PI3K) family of lipid kinases has been well conserved from yeast to mammals. In this evolutionary perspective on the PI3K family, we discuss the prototypical properties of PI3Ks: 1) the utilization of sparse but specifically localized lipid substrates; 2) the nucleation signaling complexes at membrane-targeted sites; and 3) the integration of intracellular signaling with extracellular cues. Together, these three core properties serve to establish order within the entropic environment of the cell. Many human diseases, including cancer and diabetes, are the direct result of loss or defects in one or more of these core properties, putting much hope in the clinical use of PI3K inhibitors singly and in combination to restore order within diseased tissues.
Topics: Animals; Humans; Phosphatidylinositol 3-Kinases; Phosphatidylinositols
PubMed: 20582535
DOI: 10.1007/82_2010_55