scholarly journals A mechanism for exocyst-mediated tethering via Arf6 and PIP5K1C driven phosphoinositide conversion

2021 ◽  
Author(s):  
Hannes Maib ◽  
David H Murray
Keyword(s):  
Plasma Membrane ◽  
Cell Biology ◽  
Molecular Mechanisms ◽  
Lipid Kinase ◽  
Phosphoinositide Signaling ◽  
Cargo Delivery ◽  
Membrane Tethering ◽  
Molecular Machinery ◽  
Protein Components ◽  
Phosphatidylinositol 4

Polarized trafficking is necessary for the development of eukaryotes and is regulated by a conserved molecular machinery. Late steps of cargo delivery are mediated by the exocyst complex, which integrates lipid and protein components to tether vesicles for plasma membrane fusion. However, the molecular mechanisms of this process are poorly defined. Here, we reconstitute functional octameric human exocyst, demonstrating the basis for holocomplex coalescence and biochemically stable subcomplexes. We determine that each subcomplex independently binds to phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), which is minimally sufficient for membrane tethering. Through reconstitution and epithelial cell biology experiments, we show that Arf6-mediated recruitment of the lipid kinase PIP5K1C rapidly converts phosphatidylinositol 4-phosphate (PI(4)P) to PI(4,5)P2, driving exocyst recruitment and membrane tethering. These results provide a molecular mechanism of exocyst-mediated tethering and a unique functional requirement for phosphoinositide signaling on late-stage vesicles in the vicinity of the plasma membrane.

scholarly journals Assembly of the PtdIns 4-kinase Stt4 complex at the plasma membrane requires Ypp1 and Efr3

2008 ◽  
Vol 183 (6) ◽  
pp. 1061-1074 ◽  
Author(s):  
Dan Baird ◽  
Chris Stefan ◽  
Anjon Audhya ◽  
Sabine Weys ◽  
Scott D. Emr
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Membrane Protein ◽  
Essential Gene ◽  
Additional Component ◽  
Lipid Kinase ◽  
Phosphoinositide Kinase ◽  
Multiple Copies ◽  
The Stability ◽  
Phosphatidylinositol 4

The phosphoinositide phosphatidylinositol 4-phosphate (PtdIns4P) is an essential signaling lipid that regulates secretion and polarization of the actin cytoskeleton. In Saccharomyces cerevisiae, the PtdIns 4-kinase Stt4 catalyzes the synthesis of PtdIns4P at the plasma membrane (PM). In this paper, we identify and characterize two novel regulatory components of the Stt4 kinase complex, Ypp1 and Efr3. The essential gene YPP1 encodes a conserved protein that colocalizes with Stt4 at cortical punctate structures and regulates the stability of this lipid kinase. Accordingly, Ypp1 interacts with distinct regions on Stt4 that are necessary for the assembly and recruitment of multiple copies of the kinase into phosphoinositide kinase (PIK) patches. We identify the membrane protein Efr3 as an additional component of Stt4 PIK patches. Efr3 is essential for assembly of both Ypp1 and Stt4 at PIK patches. We conclude that Ypp1 and Efr3 are required for the formation and architecture of Stt4 PIK patches and ultimately PM-based PtdIns4P signaling.

scholarly journals Phosphatidylinositol 4,5-bisphosphate is regenerated by speeding of the PI 4-kinase pathway during long PLC activation

2020 ◽  
Vol 152 (12) ◽  
Author(s):  
Jongyun Myeong ◽  
Lizbeth de la Cruz ◽  
Seung-Ryoung Jung ◽  
Jun-Hee Yeon ◽  
Byung-Chang Suh ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Plasma Membranes ◽  
Lipid Kinase ◽  
Agonist Action ◽  
Lipid Species ◽  
Phosphoinositide Cycle ◽  
M1 Muscarinic ◽  
Phosphatidylinositol 4 ◽  
Cellular Compartments ◽  
Regulatory Controls

The dynamic metabolism of membrane phosphoinositide lipids involves several cellular compartments including the ER, Golgi, and plasma membrane. There are cycles of phosphorylation and dephosphorylation and of synthesis, transfer, and breakdown. The simplified phosphoinositide cycle comprises synthesis of phosphatidylinositol in the ER, transport, and phosphorylation in the Golgi and plasma membranes to generate phosphatidylinositol 4,5-bisphosphate, followed by receptor-stimulated hydrolysis in the plasma membrane and return of the components to the ER for reassembly. Using probes for specific lipid species, we have followed and analyzed the kinetics of several of these events during stimulation of M1 muscarinic receptors coupled to the G-protein Gq. We show that during long continued agonist action, polyphosphorylated inositol lipids are initially depleted but then regenerate while agonist is still present. Experiments and kinetic modeling reveal that the regeneration results from gradual but massive up-regulation of PI 4-kinase pathways rather than from desensitization of receptors. Golgi pools of phosphatidylinositol 4-phosphate and the lipid kinase PI4KIIIα (PI4KA) contribute to this homeostatic regeneration. This powerful acceleration, which may be at the level of enzyme activity or of precursor and product delivery, reveals strong regulatory controls in the phosphoinositide cycle.

scholarly journals Fission yeast Opy1 is an endogenous PI(4,5)P2 sensor that binds to the phosphatidylinositol 4-phosphate 5-kinase Its3

2020 ◽  
Vol 133 (23) ◽  
pp. jcs247973
Author(s):  
Chloe E. Snider ◽  
Alaina H. Willet ◽  
HannahSofia T. Brown ◽  
Jun-Song Chen ◽  
Joshua M. Evers ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Cell Biology ◽  
Kinase Activity ◽  
Striking Difference ◽  
Evolutionary Divergence ◽  
Ph Domain ◽  
Phosphatidylinositol 4 ◽  
Related Proteins

ABSTRACTPhosphoinositides (PIPs) are a dynamic family of lipids that execute diverse roles in cell biology. PIP levels are regulated by numerous enzymes, but our understanding of how these enzymes are controlled in space and time is incomplete. One role of the PIP phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is to anchor the cytokinetic ring (CR) to the plasma membrane (PM) in Schizosaccharomyces pombe. While examining potential PI(4,5)P2-binding proteins for roles in CR anchoring, we identified the dual pleckstrin homology (PH) domain-containing protein Opy1. Although related proteins are implicated in PIP regulation, we found no role for S. pombe Opy1 in CR anchoring, which would be expected if it modulated PM PI(4,5)P2 levels. Our data indicate that although Opy1 senses PM PI(4,5)P2 levels and binds to the phosphatidylinositol 4-phosphate 5-kinase (PI5-kinase) Its3, Opy1 does not regulate Its3 kinase activity or PM PI(4,5)P2 levels, a striking difference from its Saccharomyces cerevisiae homolog. However, overexpression of Opy1 resulted in cytokinesis defects, as might be expected if it sequestered PI(4,5)P2. Our results highlight the evolutionary divergence of dual PH domain-containing proteins and the need for caution when interpreting results based on their overexpression.This article has an associated First Person interview with the first author of the paper.

scholarly journals Septin function tunes lipid kinase activity and phosphatidylinositol 4,5 bisphosphate turnover during G-protein coupled PLC signaling in vivo

2021 ◽  
Author(s):  
Aastha Kumari ◽  
Avishek Ghosh ◽  
Sourav Kolay ◽  
RAGHU PADINJAT
Keyword(s):  
Plasma Membrane ◽  
Kinase Activity ◽  
Electrical Response ◽  
Receptor Activation ◽  
Sensory Transduction ◽  
Photon Absorption ◽  
Lipid Kinase ◽  
Phosphatidylinositol 4

The hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] at the plasma membrane by receptor activated phospholipase C (PLC) activity is a conserved mechanism of signal transduction. Given the low abundance of PI(4,5)P2 at the plasma membrane, its hydrolysis needs to be coupled to lipid resynthesis to ensure continued PLC activity during receptor activation. However, the mechanism by which PI(4,5)P2 depletion during signalling is coupled to its resynthesis remains unknown. PI(4,5)P2 synthesis is catalyzed by lipid kinase activity and the phosphorylation of phosphatidylinositol 4 phosphate (PI4P) by phosphatidylinositol 4 phosphate 5 kinase (PIP5K) is the final step in this process. In Drosophila photoreceptors, sensory transduction of photon absorption is transduced into PLC activity leading to an electrical response to light. During this process, PI(4,5)P2 is resynthesized by a PIP5K activity but the mechanism by which the activity of this enzyme is coupled to PLC signalling is not known. In this study, we identify a unique protein isoform of dPIP5K, dPIP5KL that is both necessary and sufficient to mediate PI(4,5)P2 synthesis during phototransduction. The activity of dPIP5KL in vitro is enhanced by depletion of PNUT, a non-redundant subunit of the septin family of GTP binding proteins and in vivo, depletion of pnut rescues the effect of dPIP5KL depletion on the light response and PI(4,5)P2 resynthesis during PLC signalling. Lastly we find that depletion of Septin Interacting Protein 1 (Sip1),previously shown to bind PNUT, phenocopies the effect of dPIP5KL depletion in vivo. Thus, our work defines a septin 7 and Sip1 mediated mechanism through which PIP5K activity is coupled to ongoing PLC mediated PI(4,5)P2 depletion.

scholarly journals Membrane curvature in cell biology: An integration of molecular mechanisms

2016 ◽  
Vol 214 (4) ◽  
pp. 375-387 ◽  
Author(s):  
Iris K. Jarsch ◽  
Frederic Daste ◽  
Jennifer L. Gallop
Keyword(s):  
Cell Biology ◽  
Molecular Mechanisms ◽  
Biological Membranes ◽  
Membrane Traffic ◽  
Membrane Curvature ◽  
Future Research ◽  
Membrane Bilayer ◽  
Extrinsic Factors ◽  
Protein Components ◽  
Complex Architecture

Curving biological membranes establishes the complex architecture of the cell and mediates membrane traffic to control flux through subcellular compartments. Common molecular mechanisms for bending membranes are evident in different cell biological contexts across eukaryotic phyla. These mechanisms can be intrinsic to the membrane bilayer (either the lipid or protein components) or can be brought about by extrinsic factors, including the cytoskeleton. Here, we review examples of membrane curvature generation in animals, fungi, and plants. We showcase the molecular mechanisms involved and how they collaborate and go on to highlight contexts of curvature that are exciting areas of future research. Lessons from how membranes are bent in yeast and mammals give hints as to the molecular mechanisms we expect to see used by plants and protists.

scholarly journals Molecular regulation of Snai2 in development and disease

2019 ◽  
Vol 132 (23) ◽  
Author(s):  
Wenhui Zhou ◽  
Kayla M. Gross ◽  
Charlotte Kuperwasser
Keyword(s):  
Transcription Factor ◽  
Cell Biology ◽  
Molecular Mechanisms ◽  
Epithelial To Mesenchymal Transition ◽  
Zinc Finger Protein ◽  
Main Role ◽  
Biological Processes ◽  
Developmental Defects ◽  
Mesenchymal Transition ◽  
Damage Repair

ABSTRACT The transcription factor Snai2, encoded by the SNAI2 gene, is an evolutionarily conserved C2H2 zinc finger protein that orchestrates biological processes critical to tissue development and tumorigenesis. Initially characterized as a prototypical epithelial-to-mesenchymal transition (EMT) transcription factor, Snai2 has been shown more recently to participate in a wider variety of biological processes, including tumor metastasis, stem and/or progenitor cell biology, cellular differentiation, vascular remodeling and DNA damage repair. The main role of Snai2 in controlling such processes involves facilitating the epigenetic regulation of transcriptional programs, and, as such, its dysregulation manifests in developmental defects, disruption of tissue homeostasis, and other disease conditions. Here, we discuss our current understanding of the molecular mechanisms regulating Snai2 expression, abundance and activity. In addition, we outline how these mechanisms contribute to disease phenotypes or how they may impact rational therapeutic targeting of Snai2 dysregulation in human disease.

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