Intact Ca(2+)-binding sites are required for targeting of annexin 1 to endosomal membranes in living HeLa cells

2000 ◽  
Vol 113 (22) ◽  
pp. 3931-3938 ◽  
Author(s):  
U. Rescher ◽  
N. Zobiack ◽  
V. Gerke
Keyword(s):  
Hela Cells ◽  
Binding Sites ◽  
Fluorescent Protein ◽  
Binding Protein ◽  
Membrane Binding ◽  
Growth Factor Receptor ◽  
Intracellular Distribution ◽  
Live Cells ◽  
Membrane Structures ◽  
Annexin 1

Annexin 1 is a Ca(2+)-regulated membrane binding protein and a major substrate of the epidermal growth factor receptor kinase. Because of its properties and intracellular distribution, the protein has been implicated in endocytic trafficking of the receptor, in particular in receptor sorting occurring in multivesicular endosomes. Up to now, however, the localization of annexin 1 to cellular membranes has been limited to subcellular fractionation and immunocytochemical analyses of fixed cells. To establish its localization in live cells, we followed the intracellular fate of annexin 1 molecules fused to the Green Fluorescent Protein (GFP). We show that annexin 1-GFP associates with distinct, transferrin receptor-positive membrane structures in living HeLa cells. A GFP chimera containing the Ca(2+)/phospholipid-binding protein core of annexin 1 also shows a punctate intracellular distribution, although the structures labeled here do not resemble early but, at least in part, late endosomes. In contrast, the cores of annexins 2 and 4 fused to GFP exhibit a cytoplasmic or a different punctate distribution, respectively, indicating that the highly homologous annexin core domains carry distinct membrane specificities within live cells. By inactivating the three high-affinity Ca(2+) binding sites in annexin 1 we also show that endosomal membrane binding of the protein in live HeLa cells depends on the integrity of these Ca(2+) binding sites. More detailed analysis identifies a single Ca(2+) site in the second annexin repeat that is crucially involved in establishing the membrane association. These results reveal for the first time that intracellular membrane binding of an annexin in living cells requires Ca(2+) and is mediated in part through an annexin core domain that is capable of establishing specific interactions.

scholarly journals Grb2 Regulates Internalization of EGF Receptors through Clathrin-coated Pits

2003 ◽  
Vol 14 (3) ◽  
pp. 858-870 ◽  
Author(s):  
Xuejun Jiang ◽  
Fangtian Huang ◽  
Andriy Marusyk ◽  
Alexander Sorkin
Keyword(s):  
Growth Factor ◽  
Hela Cells ◽  
Binding Sites ◽  
Molecular Mechanisms ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Growth Factor Receptor ◽  
Receptor Internalization ◽  
Sequence Motifs ◽  
Coated Pits

The molecular mechanisms of clathrin-dependent internalization of epidermal growth factor receptor (EGFR) are not well understood and, in particular, the sequence motifs that mediate EGFR interactions with coated pits have not been mapped. We generated a panel of EGFR mutants and stably expressed these mutants in porcine aortic endothelial (PAE) cells. Interestingly, mutations of tyrosine phosphorylation sites 1068 and 1086 that interact with growth-factor-receptor-binding protein Grb2 completely abolished receptor internalization in PAE cells. Quantitative analysis of colocalization of EGF-rhodamine conjugate and coated pits labeled with yellow-fluorescent-protein–tagged β2 subunit of clathrin adaptor complex AP-2 revealed that EGFR mutants lacking Grb2 binding sites do not efficiently enter coated pits. The depletion of Grb2 from PAE as well as HeLa cells expressing endogenous EGFRs by RNA interference substantially reduced the rate of EGFR internalization through clathrin-dependent pathway, thus providing the direct evidence for the important role of Grb2 in this process. Overexpression of Grb2 mutants, in which the SH3 domains were either deleted or inactivated by point mutations, significantly inhibited EGFR internalization in both PAE and HeLa cells. These findings indicate that Grb2, in addition to its key function in signaling through Ras, has a major regulatory role at the initial steps of EGFR internalization through clathrin-coated pits. Furthermore, the EGFR mutant lacking Grb2 binding sites did not efficiently recruit c-Cbl and was not polyubiquitinated. The data are consistent with the model whereby Grb2 participates in EGFR internalization through the recruitment of Cbl to the receptor, thus allowing proper ubiquitylation of EGFR and/or associated proteins at the plasma membrane.

Lactadherin C2 Domain Exhibits Ptd-L-Ser Specificity and Anticoagulant Properties Distinct From Homologous Factor VIII C2 Domain and Full-Length Lactadherin

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1105-1105
Author(s):  
Valerie A Novakovic ◽  
Eugene R Gilbert ◽  
Jialan Shi ◽  
Gary E. Gilbert
Keyword(s):  
Factor Viii ◽  
Hela Cells ◽  
Binding Sites ◽  
Metal Ion ◽  
Membrane Binding ◽  
Full Length ◽  
Crystallographic Structure ◽  
Factor V ◽  
C2 Domain ◽  
Prothrombinase Activity

Abstract Abstract 1105 Background: Lactadherin (aka mfg-e8) is a milk-fat globule membrane protein with a domain structure of EGF1-EGF2-C1-C2, where the lectin-like C1 and C2 domains are homologous to the membrane binding domains of factor VIII and factor V. Like factor VIII and factor V, lactadherin exhibits calcium-independent membrane binding that is selective for phosphatidyl-L-serine (Ptd-L-Ser). Lactadherin also binds preferentially to convex membranes, competes efficiently for binding sites of factor VIII and factor V, and can function as an anticoagulant via competition for these binding sites. On stressed endothelial cells lactadherin binds to filopodia and the cell margins, identifying sites that have exposed Ptd-L-Ser and support assembly of the prothrombinase complex. The crystallographic structure of the lactadherin C2 domain (Lact-C2) and structure-function studies have shown that membrane binding is mediated by a longer β-hairpin turn, with different residues than fVIII-C2 and fV-C2. Further, we have shown that Lact-C2 maintains specificity for phosphatidylserine, in contrast to fVIII-C2, and that fluorescent fusion proteins containing Lact-C2 can be used as intracellular phosphatidylserine probes (Yeung et al. Science 2008;319:210). However, the extent to which Lact-C2 retains the membrane binding and anticoagulant properties of full-length lactadherin, has not been studied. Methods: Lact-C2 was produced in E. coliand purified by metal ion chromatography followed by gel filtration. Competition experiments were performed by flow cytometry using phospholipid bilayers supported by glass microspheres to determine Lact-C2's ability to block binding sites of FITC-labeled lactadherin, or fluorescein-labeled factor VIII and factor V. Lact-C2 was also labeled with FITC to measure its binding to sonicated or 100 nm diameter, extruded vesicles with varying PS content in order to assess Ptd-L-Ser selectivity and membrane curvature sensitivity. Two-step amidolytic factor Xase and prothrombinase assays were used to assess the ability of Lact-C2 to block activity. Fluorescence microscopy experiments were used to compare the binding of Alexa 647-labeled Lact-C2 vs. FITC-labeled lactadherin on staurosphorine-treated HeLa cells. Results: Lact-C2 showed stereospecific binding to Ptd-L-Ser vs. Ptd-D-Ser in vesicles of 4% and 10% PS. Lact-C2 was sensitive to vesicle curvature, detecting as little as 1% Ptd-L-Ser on sonicated vesicles but requiring 4% Ptd-L-Ser on extruded vesicles. Lact-C2 competed for 89% of lactadherin binding sites and 84% of factor VIII binding sites. Inhibition of factor Xase activity plateaued at 89% reduction vs. >99% reduction for lactadherin. Lact-C2 also competed for 61% of factor V binding sites corresponding to an 82% reduction in prothrombinase activity. We are currently comparing the distribution of binding sites for Lact-C2 vs. lactadherin on stressed HeLa cells, with preliminary data showing distinct, but overlapping, binding site distribution. Discussion: Lact-C2 exhibits stereospecific Ptd-L-Ser binding and convex curvature preference similar to full-length lactadherin. Lact-C2 contrasts with fVIII-C2 in Ptd-L-Ser specificity and capacity to compete with factor VIII and inhibit factor Xase activity and prothrombinase activity. These results provide a framework for interpreting experiments in which Lact-C2 is used as an anticoagulant or as a calcium-independent probe for exposed membrane Ptd-L-Ser. Lact-C2 is able to bind to only a subset of lactadherin binding sites, highlighting the importance of the lactadherin C1 domain for high affinity binding and underscoring the largely unappreciated complexity of phospholipid membrane binding sites. Disclosures: Shi: Brigham and Women's Hospital: Use of Lactadherin to detect phosphataidylserine, Use of Lactadherin to detect phosphataidylserine Patents & Royalties.

scholarly journals An Sfi1p-Like Centrin-Binding Protein Mediates Centrin-Based Ca2+-Dependent Contractility in Paramecium tetraurelia

2007 ◽  
Vol 6 (11) ◽  
pp. 1992-2000 ◽  
Author(s):  
Delphine Gogendeau ◽  
Janine Beisson ◽  
Nicole Garreau de Loubresse ◽  
Jean-Pierre Le Caer ◽  
Françoise Ruiz ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Binding Sites ◽  
Fluorescent Protein ◽  
Binding Protein ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
High Molecular Mass ◽  
Paramecium Tetraurelia ◽  
Protein Fusion

ABSTRACT The previous characterization and structural analyses of Sfi1p, a Saccharomyces cerevisiae centrin-binding protein essential for spindle pole body duplication, have suggested molecular models to account for centrin-mediated, Ca2+-dependent contractility processes (S. Li, A. M. Sandercock, P. Conduit, C. V. Robinson, R. L. Williams, and J. V. Kilmartin, J. Cell Biol. 173:867-877, 2006). Such processes can be analyzed by using Paramecium tetraurelia, which harbors a large Ca2+-dependent contractile cytoskeletal network, the infraciliary lattice (ICL). Previous biochemical and genetic studies have shown that the ICL is composed of diverse centrin isoforms and a high-molecular-mass centrin-associated protein, whose reduced size in the démaillé (dem1) mutant correlates with defective organization of the ICL. Using sequences derived from the high-molecular-mass protein to probe the Paramecium genome sequence, we characterized the PtCenBP1 gene, which encodes a 460-kDa protein. PtCenBP1p displays six almost perfect repeats of ca. 427 amino acids (aa) and harbors 89 potential centrin-binding sites with the consensus motif LLX11F/LX2WK/R, similar to the centrin-binding sites of ScSfi1p. The smaller (260-kDa) protein encoded by the dem1 mutant PtCenBP1 allele comprises only two repeats of 427 aa and 46 centrin-binding sites. By using RNA interference and green fluorescent protein fusion experiments, we showed that PtCenBP1p forms the backbone of the ICL and plays an essential role in its assembly and contractility. This study provides the first in vivo demonstration of the role of Sfi1p-like proteins in centrin-mediated Ca2+-dependent contractile processes.

scholarly journals Unique integrated stress response sensors regulate cancer cell susceptibility when Hsp70 activity is compromised

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Sara Sannino ◽  
Megan E Yates ◽  
Mark E Schurdak ◽  
Steffi Oesterreich ◽  
Adrian V Lee ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Stress Response ◽  
Protein Kinase ◽  
Fluorescent Protein ◽  
Binding Protein ◽  
Growth Factor Receptor ◽  
Initiation Factor ◽  
Integrated Stress Response ◽  
Activating Transcription Factor

AMPK, AMP-activated protein Kinase; AKT, AK strain Transforming serine/threonine kinase; ASNS, asparagine synthetase; ATF4, activating transcription factor 4; ATF6, activating transcription factor 6; BiP, Immunoglobulin Binding Protein; CHOP, C/EBP homologous protein; CQ, chloroquine; DTT, 1,4-Dithiothreitol; EBSS, Earle's balanced salt solution; eIF2α, eukaryotic initiation factor 2 alpha; ER, endoplasmic reticulum; ERAD, endoplasmic reticulum associated degradation; FBS, fetal bovine serum; GCN2, general control non-derepressible 2 factor; GFP, green fluorescent protein; HER2, epidermal growth factor receptor 2; HIF1α, Hypoxia Inducible Factor 1 Subunit Alpha; HRI, heme-regulated inhibitor kinase; Hsp70, heat shock protein 70; IRE1, inositol-required enzyme 1; ISR, integrated stress response; MAL3-101, phenylmethyl 4-[1,1'-biphenyl]-4-yl-1-[6-[[2-(butylamino)-1-[3-(methoxycarbonyl)-4-(2-methoxy-2-oxoethoxy)phenyl]-2-oxoethyl]hexylamino]-6-oxohexyl]-1,2,3,4-tetrahydro-6-methyl-2-oxo-5-pyrimidinecarboxylate; mTOR, mechanistic Target Of Rapamycin; PBS, phosphate buffered saline; PERK, PKR-like endoplasmic reticulum resident kinase; PI, propidium iodide; PKR, Protein Kinase RNA-activated; RFP, red fluorescent protein; RPPA, Reverse Phase Protein Array; S6K, 70‐kDa ribosomal protein S6 kinase; TNBC, triple negative breast cancer; UPR, unfolded protein response; XbpI, X-box binding protein 1.

scholarly journals Utilizing Stimulated Raman Scattering Microscopy To Study Intracellular Distribution of Label-Free Ponatinib in Live Cells

2019 ◽  
Vol 63 (5) ◽  
pp. 2028-2034 ◽  
Author(s):  
Kristel Sepp ◽  
Martin Lee ◽  
Marie T. J. Bluntzer ◽  
G. Vignir Helgason ◽  
Alison N. Hulme ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Stimulated Raman Scattering ◽  
Intracellular Distribution ◽  
Live Cells ◽  
Label Free ◽  
Stimulated Raman

scholarly journals Fluorescent Probes for Live Cell Thiol Detection

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3575
Author(s):  
Shenggang Wang ◽  
Yue Huang ◽  
Xiangming Guan
Keyword(s):  
Fluorescent Probes ◽  
Biological System ◽  
High Sensitivity ◽  
Intracellular Distribution ◽  
Live Cell ◽  
Live Cells ◽  
High Demand ◽  
Non Invasive

Thiols play vital and irreplaceable roles in the biological system. Abnormality of thiol levels has been linked with various diseases and biological disorders. Thiols are known to distribute unevenly and change dynamically in the biological system. Methods that can determine thiols’ concentration and distribution in live cells are in high demand. In the last two decades, fluorescent probes have emerged as a powerful tool for achieving that goal for the simplicity, high sensitivity, and capability of visualizing the analytes in live cells in a non-invasive way. They also enable the determination of intracellular distribution and dynamitic movement of thiols in the intact native environments. This review focuses on some of the major strategies/mechanisms being used for detecting GSH, Cys/Hcy, and other thiols in live cells via fluorescent probes, and how they are applied at the cellular and subcellular levels. The sensing mechanisms (for GSH and Cys/Hcy) and bio-applications of the probes are illustrated followed by a summary of probes for selectively detecting cellular and subcellular thiols.

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