scholarly journals Cell-surface remodelling during mammalian erythropoiesis

1982 ◽  
Vol 208 (1) ◽  
pp. 239-242 ◽  
Author(s):  
D C Wraith ◽  
C J Chesterton
Keyword(s):  
Surface Modification ◽  
Membrane Proteins ◽  
Cell Surface ◽  
Protein Composition ◽  
Surface Protein ◽  
Current Evidence ◽  
Cell Surface Protein ◽  
Erythroid Cells ◽  
Selective Loss ◽  
Before And After

Current evidence suggests that the major cell-surface modification occurring during mammalian erythropoiesis could be generated by two separate mechanisms: either selective loss of membrane proteins during enucleation or endocytosis at the subsequent reticulocyte and erythrocyte stages. The former idea was tested by collecting developing rabbit erythroid cells before and after the enucleation step and comparing their cell-surface protein composition via radiolabelling and electrophoresis. Few changes were observed. Our data thus lend support to the endocytosis mechanism.

scholarly journals Identification of phagocytosis-associated surface proteins of macrophages by two-dimensional gel electrophoresis.

1982 ◽  
Vol 92 (2) ◽  
pp. 283-288 ◽  
Author(s):  
F D Howard ◽  
H R Petty ◽  
H M McConnell
Keyword(s):  
Cell Surface ◽  
Gel Electrophoresis ◽  
Protein Composition ◽  
Surface Protein ◽  
Surface Proteins ◽  
Two Dimensional ◽  
Cell Surface Protein ◽  
Two Dimensional Gel Electrophoresis ◽  
Reducing Conditions ◽  
Membrane Components

Two-dimensional PAGE (P. Z. O'Farrell, H. M. Goodman, and P. H. O'Farrell. 1977. Cell. 12:1133-1142) has been employed to assess the effects of antibody-dependent phagocytosis on the cell surface protein composition of RAW264 macrophages. Unilamellar phospholipid vesicles containing 1% dinitrophenyl-aminocaproyl-phosphatidylethanolamine (DNP-cap-PE) were used as the target particle. Macrophages were exposed to anti-DNP antibody alone, vesicles alone, or vesicles in the presence of antibody for 1 h at 37 degrees C. Cell surface proteins were then labeled by lactoperoxidase-catalyzed radioiodination at 4 degrees C. After detergent solubilization, membrane proteins were analyzed by two-dimensional gel electrophoresis. The resulting pattern of spots was compared to that of standard proteins. We have identified several surface proteins, not apparently associated with the phagocytic process, which are present either in a multichain structure or in several discretely charged forms. After phagocytosis, we have observed the appearance of two proteins of 45 and 50 kdaltons in nonreducing gels. In addition, we have noted the disappearance of a 140-kdalton protein in gels run under reducing conditions. These alterations would not be detected in the conventional one-dimensional gel electrophoresis. This evidence shows that phagocytosis leads to a modification of cell surface protein composition. Our results support the concept of specific enrichment and depletion of membrane components during antibody-dependent phagocytosis.

scholarly journals Identification of tumorigenic cells and therapeutic targets in pancreatic neuroendocrine tumors

2016 ◽  
Vol 113 (16) ◽  
pp. 4464-4469 ◽  
Author(s):  
Geoffrey Wayne Krampitz ◽  
Benson M. George ◽  
Stephen B. Willingham ◽  
Jens-Peter Volkmer ◽  
Kipp Weiskopf ◽  
...  
Keyword(s):  
Cell Surface ◽  
Tumor Growth ◽  
Neuroendocrine Tumors ◽  
Surface Protein ◽  
Current Evidence ◽  
Cell Surface Protein ◽  
Pancreatic Neuroendocrine Tumors ◽  
Tumor Initiating Cells

Pancreatic neuroendocrine tumors (PanNETs) are a type of pancreatic cancer with limited therapeutic options. Consequently, most patients with advanced disease die from tumor progression. Current evidence indicates that a subset of cancer cells is responsible for tumor development, metastasis, and recurrence, and targeting these tumor-initiating cells is necessary to eradicate tumors. However, tumor-initiating cells and the biological processes that promote pathogenesis remain largely uncharacterized in PanNETs. Here we profile primary and metastatic tumors from an index patient and demonstrate that MET proto-oncogene activation is important for tumor growth in PanNET xenograft models. We identify a highly tumorigenic cell population within several independent surgically acquired PanNETs characterized by increased cell-surface protein CD90 expression and aldehyde dehydrogenase A1 (ALDHA1) activity, and provide in vitro and in vivo evidence for their stem-like properties. We performed proteomic profiling of 332 antigens in two cell lines and four primary tumors, and showed that CD47, a cell-surface protein that acts as a “don’t eat me” signal co-opted by cancers to evade innate immune surveillance, is ubiquitously expressed. Moreover, CD47 coexpresses with MET and is enriched in CD90hi cells. Furthermore, blocking CD47 signaling promotes engulfment of tumor cells by macrophages in vitro and inhibits xenograft tumor growth, prevents metastases, and prolongs survival in vivo.

Immunogold and immunoblot studies on a cell surface protein found in primary mesenchyme cells and in the cortical secretory vesicles of the sea urchin egg

1987 ◽  
Vol 45 ◽  
pp. 832-833
Author(s):  
G.L. Decker ◽  
M.C. Valdizan
Keyword(s):  
Cell Surface ◽  
Sea Urchin ◽  
Surface Protein ◽  
Egg Cell ◽  
Secretory Vesicles ◽  
Cell Surface Protein ◽  
Surface Complexes ◽  
Mesenchyme Cells ◽  
Lowicryl K4m ◽  
Primary Mesenchyme Cells

A monoclonal antibody designated MAb 1223 has been used to show that primary mesenchyme cells of the sea urchin embryo express a 130-kDa cell surface protein that may be directly involved in Ca2+ uptake required for growth of skeletal spicules. Other studies from this laboratory have shown that the 1223 antigen, although in relatively low abundance, is also expressed on the cell surfaces of unfertilized eggs and on the majority of blastomeres formed prior to differentiation of the primary mesenchyme cells.We have studied the distribution of 1223 antigen in S. purpuratus eggs and embryos and in isolated egg cell surface complexes that contain the cortical secretory vesicles. Specimens were fixed in 1.0% paraformaldehyde and 1.0% glutaraldehyde and embedded in Lowicryl K4M as previously reported. Colloidal gold (8nm diameter) was prepared by the method of Mulpfordt.

scholarly journals Monomer–dimer dynamics and distribution of GPI-anchored uPAR are determined by cell surface protein assemblies

2007 ◽  
Vol 179 (5) ◽  
pp. 1067-1082 ◽  
Author(s):  
Valeria R. Caiolfa ◽  
Moreno Zamai ◽  
Gabriele Malengo ◽  
Annapaola Andolfo ◽  
Chris D. Madsen ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Cell Surface ◽  
Plasminogen Activator ◽  
Fluorescent Protein ◽  
Surface Protein ◽  
Basal Membrane ◽  
Membrane Dynamics ◽  
Live Cells ◽  
Cell Surface Protein ◽  
Protein Assemblies

To search for functional links between glycosylphosphatidylinositol (GPI) protein monomer–oligomer exchange and membrane dynamics and confinement, we studied urokinase plasminogen activator (uPA) receptor (uPAR), a GPI receptor involved in the regulation of cell adhesion, migration, and proliferation. Using a functionally active fluorescent protein–uPAR in live cells, we analyzed the effect that extracellular matrix proteins and uPAR ligands have on uPAR dynamics and dimerization at the cell membrane. Vitronectin directs the recruitment of dimers and slows down the diffusion of the receptors at the basal membrane. The commitment to uPA–plasminogen activator inhibitor type 1–mediated endocytosis and recycling modifies uPAR diffusion and induces an exchange between uPAR monomers and dimers. This exchange is fully reversible. The data demonstrate that cell surface protein assemblies are important in regulating the dynamics and localization of uPAR at the cell membrane and the exchange of monomers and dimers. These results also provide a strong rationale for dynamic studies of GPI-anchored molecules in live cells at steady state and in the absence of cross-linker/clustering agents.

scholarly journals GPI-anchored cell surface protein of white koji mold

2006 ◽  
Vol 101 (1) ◽  
pp. 53-60
Author(s):  
Yojiro NAKAMURA ◽  
Hitoshi SHIMOI ◽  
Kiyoshi ITO
Keyword(s):  
Cell Surface ◽  
Surface Protein ◽  
Cell Surface Protein ◽  
Koji Mold
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