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Journal of Cell Science Aug 2023Cellular functions, such as differentiation and migration, are regulated by the extracellular microenvironment, including the extracellular matrix (ECM). Cells adhere to...
Cellular functions, such as differentiation and migration, are regulated by the extracellular microenvironment, including the extracellular matrix (ECM). Cells adhere to ECM through focal adhesions (FAs) and sense the surrounding microenvironments. Although FA proteins have been actively investigated, little is known about the lipids in the plasma membrane at FAs. In this study, we examine the lipid composition at FAs with imaging and biochemical approaches. Using the cholesterol-specific probe D4 with total internal reflection fluorescence microscopy and super-resolution microscopy, we show an enrichment of cholesterol at FAs simultaneously with FA assembly. Furthermore, we establish a method to isolate the lipid from FA-rich fractions, and biochemical quantification of the lipids reveals that there is a higher content of cholesterol and phosphatidylcholine with saturated fatty acid chains in the lipids of the FA-rich fraction than in either the plasma membrane fraction or the whole-cell membrane. These results demonstrate that plasma membrane at FAs has a locally distinct lipid composition compared to the bulk plasma membrane.
Topics: Focal Adhesions; Phosphatidylcholines; Cell Membrane; Cholesterol; Extracellular Matrix
PubMed: 37470177
DOI: 10.1242/jcs.260763 -
Cold Spring Harbor Perspectives in... Sep 2023genes are frequently mutated in cancer. The primary signaling compartment of wild-type and constitutively active oncogenic mutant RAS proteins is the inner leaflet of... (Review)
Review
genes are frequently mutated in cancer. The primary signaling compartment of wild-type and constitutively active oncogenic mutant RAS proteins is the inner leaflet of the plasma membrane (PM). Thus, a better understanding of the unique environment of the PM inner leaflet is important to shed further light on RAS function. Over the past few decades, an integrated approach of superresolution imaging, molecular dynamic simulations, and biophysical assays has yielded new insights into the capacity of RAS proteins to sort lipids with specific headgroups and acyl chains, to assemble signaling nanoclusters on the inner PM. RAS proteins also sense and respond to changes in components of the outer PM leaflet, including glycophosphatidylinositol-anchored proteins, sphingophospholipids, glycosphingolipids, and galectins, as well as cholesterol that translocates between the two leaflets. Such communication between the inner and outer leaflets of the PM, called interleaflet coupling, allows RAS to potentially integrate extracellular mechanical and electrostatic information with intracellular biochemical signaling events, and reciprocally allows mutant RAS-transformed tumor cells to modify tumor microenvironments. Here, we review RAS-lipid interactions and speculate on potential mechanisms that allow communication between the opposing leaflets of the PM.
Topics: Humans; ras Proteins; Cell Membrane; Neoplasms; Signal Transduction; Tumor Microenvironment
PubMed: 37463719
DOI: 10.1101/cshperspect.a041414 -
Cells Nov 2023Endothelial cells are the crucial inner lining of blood vessels, which are pivotal in vascular homeostasis and integrity. However, these cells are perpetually subjected... (Review)
Review
Endothelial cells are the crucial inner lining of blood vessels, which are pivotal in vascular homeostasis and integrity. However, these cells are perpetually subjected to a myriad of mechanical, chemical, and biological stresses that can compromise their plasma membranes. A sophisticated repair system involving key molecules, such as calcium, annexins, dysferlin, and MG53, is essential for maintaining endothelial viability. These components orchestrate complex mechanisms, including exocytosis and endocytosis, to repair membrane disruptions. Dysfunctions in this repair machinery, often exacerbated by aging, are linked to endothelial cell death, subsequently contributing to the onset of atherosclerosis and the progression of cardiovascular diseases (CVD) and stroke, major causes of mortality in the United States. Thus, identifying the core machinery for endothelial cell membrane repair is critically important for understanding the pathogenesis of CVD and stroke and developing novel therapeutic strategies for combating CVD and stroke. This review summarizes the recent advances in understanding the mechanisms of endothelial cell membrane repair. The future directions of this research area are also highlighted.
Topics: Humans; Endothelial Cells; Cell Membrane; Membranes; Cardiovascular Diseases; Stroke
PubMed: 37998383
DOI: 10.3390/cells12222648 -
The EMBO Journal Dec 2023Alpha-synuclein (aSN) is a membrane-associated and intrinsically disordered protein, well known for pathological aggregation in neurodegeneration. However, the...
Alpha-synuclein (aSN) is a membrane-associated and intrinsically disordered protein, well known for pathological aggregation in neurodegeneration. However, the physiological function of aSN is disputed. Pull-down experiments have pointed to plasma membrane Ca -ATPase (PMCA) as a potential interaction partner. From proximity ligation assays, we find that aSN and PMCA colocalize at neuronal synapses, and we show that calcium expulsion is activated by aSN and PMCA. We further show that soluble, monomeric aSN activates PMCA at par with calmodulin, but independent of the autoinhibitory domain of PMCA, and highly dependent on acidic phospholipids and membrane-anchoring properties of aSN. On PMCA, the key site is mapped to the acidic lipid-binding site, located within a disordered PMCA-specific loop connecting the cytosolic A domain and transmembrane segment 3. Our studies point toward a novel physiological role of monomeric aSN as a stimulator of calcium clearance in neurons through activation of PMCA.
Topics: Calcium; alpha-Synuclein; Plasma Membrane Calcium-Transporting ATPases; Cell Membrane; Adenosine Triphosphatases; Binding Sites
PubMed: 37916890
DOI: 10.15252/embj.2022111122 -
The New Phytologist Aug 2023Secretion is a fundamental process that plant pathogens utilize to deliver effectors into the host to downregulate immunity and promote infection. Here, we uncover a...
Secretion is a fundamental process that plant pathogens utilize to deliver effectors into the host to downregulate immunity and promote infection. Here, we uncover a fascinating membrane trafficking and delivery route that originates from vacuolar membranes in Magnaporthe oryzae and conduits to the host interface and plasma membrane. To perform such secretory/trafficking function, MoRab7 first recruits the retromer complex to the vacuolar membrane, enabling recognition of a family of SNARE proteins, including MoSnc1. Live-cell imaging confirmed a highly dynamic vesicular trafficking of the retromer complex component(s) and MoSnc1 toward and across the host interface or plasma membrane, and subsequent fusion with target membranes. Interestingly, disruption of the MoRab7/Retromer/MoSnc1-based endolysosomal cascade affects effector secretion and fungal pathogenicity. Taken together, we discovered an unconventional protein and membrane trafficking route starting from the fungal endolysosomes to the M. oryzae-rice interaction interface and dissect the role of MoRab7/Retromer/MoSnc1 sorting machinery in effector secretion during biotrophy and invasive growth in rice blast fungus.
Topics: Endosomes; Protein Transport; Vacuoles; Biological Transport; Cell Membrane; Magnaporthe; Oryza; Fungal Proteins; Plant Diseases
PubMed: 37291895
DOI: 10.1111/nph.19050 -
Trends in Biochemical Sciences Dec 2023In T cells, stromal interaction molecule (STIM) and Orai are dispensable for conventional T cell development, but critical for activation and differentiation. This... (Review)
Review
In T cells, stromal interaction molecule (STIM) and Orai are dispensable for conventional T cell development, but critical for activation and differentiation. This review focuses on novel STIM-dependent mechanisms for control of Ca signals during T cell activation and its impact on mitochondrial function and transcriptional activation for control of T cell differentiation and function. We highlight areas that require further work including the roles of plasma membrane Ca ATPase (PMCA) and partner of STIM1 (POST) in controlling Orai function. A major knowledge gap also exists regarding the independence of T cell development from STIM and Orai, despite compelling evidence that it requires Ca signals. Resolving these and other outstanding questions ensures that the field will remain active for many years to come.
Topics: ORAI1 Protein; Stromal Interaction Molecule 1; Cell Membrane; Cell Differentiation; Calcium; Calcium Signaling
PubMed: 37696713
DOI: 10.1016/j.tibs.2023.08.006 -
Neurologia 2023Rafts are protein-lipid structural nanodomains involved in efficient signal transduction and the modulation of physiological processes of the cell plasma membrane. Raft... (Review)
Review
INTRODUCTION
Rafts are protein-lipid structural nanodomains involved in efficient signal transduction and the modulation of physiological processes of the cell plasma membrane. Raft disruption in the nervous system has been associated with a wide range of disorders.
DEVELOPMENT
We review the concept of rafts, the nervous system processes in which they are involved, and their role in diseases such as Parkinson's disease, Alzheimer disease, and Huntington disease.
CONCLUSIONS
Based on the available evidence, preservation and/or reconstitution of rafts is a promising treatment strategy for a wide range of neurological disorders.
Topics: Humans; Caveolae; Membrane Microdomains; Cholesterol; Cell Membrane; Alzheimer Disease
PubMed: 37858892
DOI: 10.1016/j.nrleng.2023.10.003 -
Nature Communications Aug 2023Junctions between the endoplasmic reticulum (ER) and the plasma membrane (PM) are specialized membrane contacts ubiquitous in eukaryotic cells. Concentration of...
Junctions between the endoplasmic reticulum (ER) and the plasma membrane (PM) are specialized membrane contacts ubiquitous in eukaryotic cells. Concentration of intracellular signaling machinery near ER-PM junctions allows these domains to serve critical roles in lipid and Ca signaling and homeostasis. Subcellular compartmentalization of protein kinase A (PKA) signaling also regulates essential cellular functions, however, no specific association between PKA and ER-PM junctional domains is known. Here, we show that in brain neurons type I PKA is directed to Kv2.1 channel-dependent ER-PM junctional domains via SPHKAP, a type I PKA-specific anchoring protein. SPHKAP association with type I PKA regulatory subunit RI and ER-resident VAP proteins results in the concentration of type I PKA between stacked ER cisternae associated with ER-PM junctions. This ER-associated PKA signalosome enables reciprocal regulation between PKA and Ca signaling machinery to support Ca influx and excitation-transcription coupling. These data reveal that neuronal ER-PM junctions support a receptor-independent form of PKA signaling driven by membrane depolarization and intracellular Ca, allowing conversion of information encoded in electrical signals into biochemical changes universally recognized throughout the cell.
Topics: Signal Transduction; Brain; Cell Membrane; Endoplasmic Reticulum; Neurons
PubMed: 37633939
DOI: 10.1038/s41467-023-40930-6 -
The Journal of Cell Biology Dec 2023Sphingomyelin plays a key role in cellular cholesterol homeostasis by binding to and sequestering cholesterol in the plasma membrane. We discovered that synthesis of...
Sphingomyelin plays a key role in cellular cholesterol homeostasis by binding to and sequestering cholesterol in the plasma membrane. We discovered that synthesis of very long chain (VLC) sphingomyelins is inversely regulated by cellular cholesterol levels; acute cholesterol depletion elicited a rapid induction of VLC-sphingolipid synthesis, increased trafficking to the Golgi apparatus and plasma membrane, while cholesterol loading reduced VLC-sphingolipid synthesis. This sphingolipid-cholesterol metabolic axis is distinct from the sterol responsive element binding protein pathway as it requires ceramide synthase 2 (CerS2) activity, epidermal growth factor receptor signaling, and was unaffected by inhibition of protein translation. Depletion of VLC-ceramides reduced plasma membrane cholesterol content, reduced plasma membrane lipid packing, and unexpectedly resulted in the accumulation of cholesterol in the cytoplasmic leaflet of the lysosome membrane. This study establishes the existence of a cholesterol-sphingolipid regulatory axis that maintains plasma membrane lipid homeostasis via regulation of sphingomyelin synthesis and trafficking.
Topics: Cell Membrane; Cytoplasm; Homeostasis; Intracellular Membranes; Sphingomyelins; Sphingosine N-Acyltransferase; Cholesterol; ErbB Receptors
PubMed: 37787764
DOI: 10.1083/jcb.202308055 -
Nature Communications Jul 2023Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly...
Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly dynamic nano-assemblies at the plasma membrane. However, little is known regarding the role of oncogenic APC in reshaping Wnt nanodomains. This is noteworthy, because oncogenic APC does not act autonomously and requires activation of Wnt effectors upstream of APC to drive aberrant Wnt signaling. Here, we demonstrate the role of oncogenic APC in increasing plasma membrane free cholesterol and rigidity, thereby modulating Wnt signaling hubs. This results in an overactivation of Wnt signaling in the colon. Finally, using the Drosophila sterol auxotroph model, we demonstrate the unique ability of exogenous free cholesterol to disrupt plasma membrane homeostasis and drive Wnt signaling in a wildtype APC background. Collectively, these findings provide a link between oncogenic APC, loss of plasma membrane homeostasis and CRC development.
Topics: Animals; beta Catenin; Carcinogenesis; Cell Membrane; Colon; Drosophila; Wnt Signaling Pathway
PubMed: 37468468
DOI: 10.1038/s41467-023-39640-w