Receptor tyrosine kinases such as EGF receptor (EGFR) stimulate phosphoinositide 3 kinases to convert phosphatidylinositol-4,5-bisphosophate [PtdIns(4,5)P] into phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P]. PtdIns(3,4,5)P then remodels actin and gene expression, and boosts cell survival and proliferation. PtdIns(3,4,5)P partly achieves these functions by triggering activation of the kinase Akt, which phosphorylates targets like Tsc2 and GSK3β.
View Article and Find Full Text PDFInternalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTKs) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumor pheochromocytoma (PCC) can be caused by activating mutations of the rearranged during transfection (RET) receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumor suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood.
View Article and Find Full Text PDFThe function of a protein within a cell critically depends on its interaction with other proteins as well as its subcellular localization. The expression of mutants of a particular protein that have selective perturbation of specific protein interaction motifs is a very useful strategy for resolving a protein's mechanism of action in a cellular process. In addition, expression of fluorescent protein fusions is a key strategy for determining the subcellular localization of a protein.
View Article and Find Full Text PDFCardiolipin and phosphatidylinositol along with the latter's phosphorylated derivative phosphoinositides, control a wide range of cellular functions from signal transduction, membrane traffic, mitochondrial function, cytoskeletal dynamics, and cell metabolism. An emerging dimension to these lipids is the specificity of their fatty acyl chains that is remarkably distinct from that of other glycerophospholipids. Cardiolipin and phosphatidylinositol undergo acyl remodeling involving the sequential actions of phospholipase A to hydrolyze acyl chains and key acyltransferases that re-acylate with specific acyl groups.
View Article and Find Full Text PDFThe epidermal growth factor receptor (EGFR) is a central regulator of cell physiology that is stimulated by multiple distinct ligands. Although ligands bind to EGFR while the receptor is exposed on the plasma membrane, EGFR incorporation into endosomes following receptor internalization is an important aspect of EGFR signaling, with EGFR internalization behavior dependent upon the type of ligand bound. We develop quantitative modeling for EGFR recruitment to and internalization from clathrin domains, focusing on how internalization competes with ligand unbinding from EGFR.
View Article and Find Full Text PDFInternalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTK) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumour pheochromocytoma (PCC) can be caused by activating mutations of the RET receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumour suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood.
View Article and Find Full Text PDFThe dynamics of living cells can be studied by live-cell fluorescence microscopy. However, this requires the use of excessive light energy to obtain good signal-to-noise ratio, which can then photobleach fluorochromes, and more worrisomely, lead to phototoxicity. Upon light excitation, noble metal nanoparticles such as silver nanoparticles (AgNPs) generate plasmons, which can then amplify excitation in direct proximity of the nanoparticle's surface and couple to the oscillating dipole of nearby radiating fluorophores, modifying their rate of emission and thus, enhancing their fluorescence.
View Article and Find Full Text PDFElevated blood glucose following a meal is cleared by insulin-stimulated glucose entry into muscle and fat cells. The hormone increases the amount of the glucose transporter GLUT4 at the plasma membrane in these tissues at the expense of preformed intracellular pools. In addition, muscle contraction also increases glucose uptake via a gain in GLUT4 at the plasma membrane.
View Article and Find Full Text PDFThe epidermal growth factor receptor (EGFR) is a central regulator of cell physiology. EGFR is activated by ligand binding, triggering receptor dimerization, activation of kinase activity, and intracellular signaling. EGFR is transiently confined within various plasma membrane nanodomains, yet how this may contribute to regulation of EGFR ligand binding is poorly understood.
View Article and Find Full Text PDFClathrin-mediated endocytosis (CME) controls the internalization and function of a wide range of cell surface proteins. CME occurs by the assembly of clathrin and many other proteins on the inner leaflet of the plasma membrane into clathrin-coated pits (CCPs). These structures recruit specific cargo destined for internalization, generate membrane curvature, and in many cases undergo scission from the plasma membrane to yield intracellular vesicles.
View Article and Find Full Text PDFThe epidermal growth factor receptor (EGFR) controls many cellular functions. Upon binding its ligand, the receptor undergoes dimerization, phosphorylation and activation of signals including the phosphoinositide-3-kinase (PI3K)-Akt pathway. Although some studies have indicated that EGFR signaling may be controlled by signal enrichment within various membrane rafts, such as flotillin nanodomains, others have found a limited effect of disruption of these nanodomains on EGFR signaling, suggesting that specific factors may define context-specific control of EGFR signaling.
View Article and Find Full Text PDFUltrasound-stimulated microbubble (USMB) treatment is a promising strategy for cancer therapy. USMB promotes drug delivery by sonoporation and enhanced endocytosis, and also impairs cell viability. However, USMB elicits heterogeneous effects on cell viability, with apparently minimal effects on a subset of cells.
View Article and Find Full Text PDFPhosphatidylinositol-3-kinases (PI3Ks) are lipid kinases that produce 3-phosphorylated derivatives of phosphatidylinositol upon activation by various cues. These 3-phosphorylated lipids bind to various protein effectors to control many cellular functions. Lipid phosphatases such as phosphatase and tensin homolog (PTEN) terminate PI3K-derived signals and are critical to ensure appropriate signaling outcomes.
View Article and Find Full Text PDFBiochim Biophys Acta Mol Cell Res
December 2022
The epidermal growth factor receptor (EGFR) triggers the activation of many intracellular signals that control cell proliferation, growth, survival, migration, and differentiation. Given its wide expression, EGFR has many functions in development and tissue homeostasis. Some of the cellular outcomes of EGFR signaling involve alterations of specific aspects of cellular metabolism, and alterations of cell metabolism are emerging as driving influences in many physiological and pathophysiological contexts.
View Article and Find Full Text PDFThe spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses mediates host cell entry and is S-acylated on multiple phylogenetically conserved cysteine residues. Multiple protein acyltransferase enzymes have been reported to post-translationally modify spike proteins; however, strategies to exploit this modification are lacking. Using resin-assisted capture MS, we demonstrate that the spike protein is S-acylated in SARS-CoV-2-infected human and monkey epithelial cells.
View Article and Find Full Text PDFThe epidermal growth factor (EGF) receptor (EGFR) controls many aspects of cell physiology. EGF binding to EGFR elicits the membrane recruitment and activation of phosphatidylinositol-3-kinase, leading to Akt phosphorylation and activation. Concomitantly, EGFR is recruited to clathrin-coated pits (CCPs), eventually leading to receptor endocytosis.
View Article and Find Full Text PDFThe COVID-19 pandemic has highlighted the urgent need for the identification of new antiviral drug therapies for a variety of diseases. COVID-19 is caused by infection with the human coronavirus SARS-CoV-2, while other related human coronaviruses cause diseases ranging from severe respiratory infections to the common cold. We developed a computational approach to identify new antiviral drug targets and repurpose clinically-relevant drug compounds for the treatment of a range of human coronavirus diseases.
View Article and Find Full Text PDFChronic pain has been widely recognized as a major public health problem that impacts multiple aspects of patient quality of life. Unfortunately, chronic pain is often resistant to conventional analgesics, which are further limited by their various side effects. New therapeutic strategies and targets are needed to better serve the millions of people suffering from this devastating disease.
View Article and Find Full Text PDFBiological research and many cell-based therapies rely on the successful delivery of cargo materials into cells. Intracellular delivery in an in vitro setting refers to a variety of physical and biochemical techniques developed for conducting rapid and efficient transport of materials across the plasma membrane. Generally, the techniques that are time-efficient (e.
View Article and Find Full Text PDFGlycans on proteins and cell surfaces are useful biomarkers for determining functional interactions with glycan binding proteins, potential disease states, or indeed level of differentiation. The ability to rapidly and sensitively detect or tag specific glycans on proteins provides a diagnostic tool with wide application in chemical glycobiology. The monosaccharide N-acetylneuraminic acid (sialic acid) is a key player in these interactions and the manipulation and control of sialylation levels has been an important research focus, particularly in the development of therapeutic proteins.
View Article and Find Full Text PDFThe dynamic phosphorylation of phosphatidylinositol produces seven distinct but interconvertible phosphatidylinositol phosphates (PIPs). Each PIP exhibits specific enrichment in a subset of membrane compartments as a result of dynamic phosphorylation and dephosphorylation by lipid kinases and phosphatases, and/or by vesicle-mediated transport. Several PIPs are found within the plasma membrane, such as phosphatidylinositol-4-phosphate [PI(4)P], phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2], and phosphatidylinositol-3,4,5-trisphosphate (PIP3), and these control many aspects of cell physiology, including receptor signaling and membrane traffic.
View Article and Find Full Text PDFAntibody combinations targeting cell surface receptors are a new modality of cancer therapy. The trafficking and signalling mechanisms regulated by such therapeutics are not fully understood but could underlie differential tumour responses. We explored EGFR trafficking upon treatment with the antibody combination Sym004 which has shown promise clinically.
View Article and Find Full Text PDFCellular uptake is limiting for the efficacy of many cytotoxic drugs used to treat cancer. Identifying endocytic mechanisms that can be modulated with targeted, clinically-relevant interventions is important to enhance the efficacy of various cancer drugs. We identify that flotillin-dependent endocytosis can be targeted and upregulated by ultrasound and microbubble (USMB) treatments to enhance uptake and efficacy of cancer drugs such as cisplatin.
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