scholarly journals Role of the glycoprotein IIb-IIIa complex in plasma membrane Ca2+ transport: a comparison of results obtained with platelets and human erythroleukemia cells

Blood ◽  
1991 ◽  
Vol 78 (11) ◽  
pp. 2887-2893 ◽  
Author(s):  
Z Suldan ◽  
LF Brass
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Rate Constants ◽  
Specific Monoclonal Antibody ◽  
Direct Role ◽  
Fibrinogen Receptor ◽  
Erythroleukemia Cells ◽  
Discernible Effect ◽  
Hel Cells

Abstract Several studies have suggested that the glycoprotein (GP) IIb-IIIa complex, which serves as the platelet fibrinogen receptor, also plays a role in the regulation of Ca2+ influx across the platelet plasma membrane. To examine this possibility further, we have compared Ca2+ transport in platelets and human erythroleukemia (HEL) cells, a megakaryoblastic cell line which synthesizes GP IIb-IIIa complexes that appear to be identical to those found on platelets. As with platelets, the results show the presence in unstimulated HEL cells of a rapidly exchangeable cytosolic Ca2+ pool that is in equilibrium with an intracellular sequestered Ca2+ pool and with extracellular Ca2+. Allowing for differences in cell size, the rate constants for Ca2+ exchange in HEL cells were similar to those in platelets. As in platelets, thrombin caused an increase in cytosolic Ca2+ that was due partly to enhanced Ca2+ influx and partly to the mobilization of internal Ca2+ stores. Incubation of the HEL cells with EDTA at 37 degrees C irreversibly altered the GP IIb-IIIa complex as evidenced by decreased binding of a complex-specific monoclonal antibody. In platelets this was accompanied by a 40% decrease in the rate of Ca2+ influx. However, in HEL cells there was neither a diminution in Ca2+ influx nor a reduction in the magnitude of the increase in cytosolic Ca2+ caused by thrombin. These results show that the parameters of Ca2+ distribution and movement are similar in HEL cells and platelets and that in HEL cells, as in platelets, the GP IIb-IIIa complex can be altered by removing Ca2+. However, unlike platelets, dissociation of the HEL cell IIb-IIIa complex has no discernible effect on plasma membrane Ca2+ transport. This suggests that earlier observations in platelets correlating changes in the rate of Ca2+ influx with changes in the number of intact IIb-IIIa complexes reflect an indirect, rather than a direct, role of these proteins in Ca2+ transport.

scholarly journals Role of the glycoprotein IIb-IIIa complex in plasma membrane Ca2+ transport: a comparison of results obtained with platelets and human erythroleukemia cells

Blood ◽  
1991 ◽  
Vol 78 (11) ◽  
pp. 2887-2893
Author(s):  
Z Suldan ◽  
LF Brass
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Rate Constants ◽  
Specific Monoclonal Antibody ◽  
Direct Role ◽  
Fibrinogen Receptor ◽  
Erythroleukemia Cells ◽  
Discernible Effect ◽  
Hel Cells

Several studies have suggested that the glycoprotein (GP) IIb-IIIa complex, which serves as the platelet fibrinogen receptor, also plays a role in the regulation of Ca2+ influx across the platelet plasma membrane. To examine this possibility further, we have compared Ca2+ transport in platelets and human erythroleukemia (HEL) cells, a megakaryoblastic cell line which synthesizes GP IIb-IIIa complexes that appear to be identical to those found on platelets. As with platelets, the results show the presence in unstimulated HEL cells of a rapidly exchangeable cytosolic Ca2+ pool that is in equilibrium with an intracellular sequestered Ca2+ pool and with extracellular Ca2+. Allowing for differences in cell size, the rate constants for Ca2+ exchange in HEL cells were similar to those in platelets. As in platelets, thrombin caused an increase in cytosolic Ca2+ that was due partly to enhanced Ca2+ influx and partly to the mobilization of internal Ca2+ stores. Incubation of the HEL cells with EDTA at 37 degrees C irreversibly altered the GP IIb-IIIa complex as evidenced by decreased binding of a complex-specific monoclonal antibody. In platelets this was accompanied by a 40% decrease in the rate of Ca2+ influx. However, in HEL cells there was neither a diminution in Ca2+ influx nor a reduction in the magnitude of the increase in cytosolic Ca2+ caused by thrombin. These results show that the parameters of Ca2+ distribution and movement are similar in HEL cells and platelets and that in HEL cells, as in platelets, the GP IIb-IIIa complex can be altered by removing Ca2+. However, unlike platelets, dissociation of the HEL cell IIb-IIIa complex has no discernible effect on plasma membrane Ca2+ transport. This suggests that earlier observations in platelets correlating changes in the rate of Ca2+ influx with changes in the number of intact IIb-IIIa complexes reflect an indirect, rather than a direct, role of these proteins in Ca2+ transport.

Spreading of a sperm surface antigen within the plasma membrane of the egg after fertilization in the rat

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 259-270
Author(s):  
Stephen J. Gaunt
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Guinea Pig ◽  
Surface Antigen ◽  
Plasma Membranes ◽  
Entire Surface ◽  
Sperm Tail ◽  
Sperm Surface ◽  
Sperm Antigens

The rat sperm surface antigen 2D6, located over the entire surface of the spermatozoon, is shown by use of a monoclonal antibody in indirect immunofluorescence experiments to spread laterally over the surface of the egg after fusion of sperm and egg plasma membranes at fertilization. Freshly fertilized eggs, obtained from superovulated rats 14h after hCG injection, showed the 2D6 antigen to have spread in a gradient over a discrete fan-shaped area of the egg surface anterior to the protruding sperm tail. Eggs at a later stage of sperm incorporation, obtained 20 h after hCG injection, snowed that the spread of antigen had extended to cover most or all of their surfaces. By 40 h after hCG injection, the approximate time that fertilized eggs cleaved to form 2-cell embryos, most of the 2D6 antigen had been lost from the cell surface. Fertilized eggs, but not unfertilized eggs or 2-cell embryos, were lysed by 2D6 monoclonal antibody in the presence of guinea pig complement. A model for sperm-egg fusion is presented to account for the observed pattern of spreading shown by the 2D6 antigen. The possible role of sperm antigens on the egg surface is discussed.

Internalisation of the type I angiotensin II receptor (ATI) and angiotensin II function in the rat adrenal zona glomerulosa cell.

1994 ◽  
Vol 141 (2) ◽  
pp. R5-R9 ◽  
Author(s):  
G. P. Vinson ◽  
M. M. Ho. ◽  
J.R. Puddefoot ◽  
R. Teja ◽  
S. Barker
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Angiotensin Ii ◽  
Zona Glomerulosa ◽  
Type I ◽  
Specific Monoclonal Antibody ◽  
Angiotensin Ii Receptor ◽  
Cellular Localisation ◽  
Glomerulosa Cells

ABSTRACT Little is known about the cellular localisation of the angiotensin II (AII) type 1 receptor (ATI) in the rat adrenal glomerulosa cell, but some studies have suggested that receptor internalisation and recycling may occur. Using a specific monoclonal antibody (6313/G2) to the first extracellular domain, we show here that most of the receptor is internalised in the unstimulated cell. When viable glomerulosa cells are incubated with 6313/G2, the receptor is transiently concentrated on the cell surface, and aldosterone output is stimulated. This stimulated output is enhanced by neither threshold nor maximal stimulatory concentrations of All amide, although the antibody does not inhibit All binding to the receptor. Conversely, the stimulatory actions of the antibody and those of ACTH are additive. The data suggest that recycling to the plasma membrane is constitutive, or regulated by unknown factors. Retention of the ATI receptor in the membrane is alone enough to allow sufficient G protein interaction to generate maximal stimulatory events.

scholarly journals Electrostatic and Hydrophobic Interactions Differentially Tune Membrane Binding Kinetics of the C2 Domain of Protein Kinase Cα

2013 ◽  
Vol 288 (23) ◽  
pp. 16905-16915 ◽  
Author(s):  
Angela M. Scott ◽  
Corina E. Antal ◽  
Alexandra C. Newton
Keyword(s):  
Plasma Membrane ◽  
Protein Kinase ◽  
Rate Constants ◽  
Electrostatic Interactions ◽  
Hydrophobic Interactions ◽  
Dissociation Rate ◽  
C2 Domain ◽  
Pkc Isozymes ◽  
Dissociation Rate Constants

The cellular activation of conventional protein kinase C (PKC) isozymes is initiated by the binding of their C2 domains to membranes in response to elevations in intracellular Ca2+. Following this C2 domain-mediated membrane recruitment, the C1 domain binds its membrane-embedded ligand diacylglycerol, resulting in activation of PKC. Here we explore the molecular mechanisms by which the C2 domain controls the initial step in the activation of PKC. Using stopped-flow fluorescence spectroscopy to measure association and dissociation rate constants, we show that hydrophobic interactions are the major driving force in the binding of the C2 domain to anionic membranes, whereas electrostatic interactions dominate in membrane retention. Specifically, mutation of select hydrophobic or select basic residues in the Ca2+-binding loops reduces membrane affinity by distinct mechanisms; mutation of hydrophobic residues primarily alters association rate constants, whereas mutation of charged residues affects dissociation rate constants. Live cell imaging reveals that introduction of these mutations into full-length PKCα not only reduces the Ca2+-dependent translocation to plasma membrane but, by impairing the plasma membrane-sensing role of the C2 domain, causes phorbol ester-triggered redistribution of PKCα to other membranes, such as the Golgi. These data underscore the key role of the C2 domain in driving conventional PKC isozymes to the plasma membrane and reveal that not only the amplitude but also the subcellular location of conventional PKC signaling can be tuned by altering the affinity of this module for membranes.

Chimaeras reveal the role of the catalytic core in the activation of the plasma membrane Ca2+ pump

2001 ◽  
Vol 356 (1) ◽  
pp. 241-245 ◽  
Author(s):  
William BA-THEIN ◽  
Ariel J. CARIDE ◽  
Ágnes ENYEDI ◽  
Katalin PÁSZTY ◽  
Cynthia L. CROY ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rate Constants ◽  
Regulatory Region ◽  
Calcium Pump ◽  
Cytoplasmic Loop ◽  
Catalytic Core ◽  
Basal Activity ◽  
N Terminus ◽  
Cytoplasmic Loops

Isoform 2b of the plasma membrane calcium pump differs from the ubiquitous isoform 4b in the following: (a) higher basal activity in the absence of calmodulin; (b) higher affinity for calmodulin; and (c) higher affinity for Ca2+ in the presence of calmodulin [Elwess, Filoteo, Enyedi and Penniston (1997) J. Biol. Chem. 272, 17981–17986]. To investigate which parts of the molecule determine these kinetic differences, we made four chimaeric constructs in which portions of isoform 2b were grafted into isoform 4b: chimaera I contains only the C-terminal regulatory region of isoform 2b; chimaera II contains the N-terminal moiety of isoform 2b, including both cytoplasmic loops; chimaera III contains the sequence of isoform 2b starting from the N-terminus to after the end of the first (small) cytoplasmic loop; and chimaera IV contains only the second (large) cytoplasmic loop. Surprisingly, chimaera I showed low basal activity in the absence of calmodulin and low affinity for calmodulin, unlike isoform 2b. In contrast, the chimaera containing both loops showed high basal activity, and Ca2+ activation curves (both in the absence and in the presence of calmodulin) similar to those of isoform 2b. The rates of activation by calmodulin and of inactivation by calmodulin removal were measured, and the apparent Kd for calmodulin was calculated from the ratio between these rate constants. The order of affinity was: 2b = II>4b = IV>III = I. From these results it is clear that the construct that most closely resembles isoform 2b is chimaera II. This shows that, in order to obtain an enzyme with properties similar to those of isoform 2b, both cytoplasmic loops are needed.

scholarly journals Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence.

1990 ◽  
Vol 111 (1) ◽  
pp. 69-78 ◽  
Author(s):  
C P Blobel ◽  
D G Myles ◽  
P Primakoff ◽  
J M White
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Developmental Stages ◽  
Biochemical Properties ◽  
Proteolytic Processing ◽  
Molecular Forms ◽  
Membrane Glycoprotein ◽  
Processing Step

A protein located on the surface of guinea pig sperm (PH-30) has been implicated in the process of sperm-egg fusion (Primakoff, P., H. Hyatt, and J. Tredick-Kline. 1987. J. Cell Biol. 104:141-149). In this paper we have assessed basic biochemical properties of PH-30 and have analyzed the molecular forms of PH-30 present at different stages of sperm maturation. We show the following: (a) PH-30 is an integral membrane glycoprotein; (b) it is composed of two tightly associated and immunologically distinct subunits; (c) both subunits are made as larger precursors; (d) processing of the two subunits occurs at different developmental stages; (e) the final processing step occurs in the region of the epididymis where sperm become fertilization competent; (f) processing can be mimicked in vitro; (g) processing exposes at least two new epitopes on PH-30-one of the newly exposed epitopes is recognized by a fusion-inhibitory monoclonal antibody. These results are discussed in terms of the possible role of PH-30 in mediating fusion with the egg plasma membrane.

scholarly journals A protein kinase C isozyme is translocated to cytoskeletal elements on activation.

1990 ◽  
Vol 1 (9) ◽  
pp. 693-706 ◽  
Author(s):  
D Mochly-Rosen ◽  
C J Henrich ◽  
L Cheever ◽  
H Khaner ◽  
P C Simpson
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Biological Effects ◽  
Specific Monoclonal Antibody ◽  
Cell Contractility ◽  
Protein Substrates ◽  
Kinase C ◽  
Cytoskeletal Elements

Protein kinase C (PKC)1 isozymes comprise a family of related cytosolic kinases that translocate to the cell particulate fraction on stimulation. The activated enzyme is thought to be on the plasma membrane. However, phosphorylation of protein substrates occurs throughout the cell and is inconsistent with plasma membrane localization. Using an isozyme-specific monoclonal antibody we found that, on activation, this PKC isozyme translocates to myofibrils in cardiac myocytes and to microfilaments in fibroblasts. Translocation of this activated PKC isozyme to cytoskeletal elements may explain some of the effects of PKC on cell contractility and morphology. In addition, differences in the translocation site of individual isozymes--and, therefore, phosphorylation of different substrates localized at these sites--may explain the diverse biological effects of PKC.

A possible biological role of boar sperm diaphorase investigated by a specific monoclonal antibody

1992 ◽  
Vol 29 (3-4) ◽  
pp. 275-288 ◽  
Author(s):  
M. Mollova ◽  
B. Atanassov ◽  
M. Ivanova ◽  
S. Kyurkchiev
Keyword(s):  
Monoclonal Antibody ◽  
Biological Role ◽  
Specific Monoclonal Antibody ◽  
Boar Sperm

scholarly journals Quantitation of membrane glycoprotein IIIa on intact human platelets using the monoclonal antibody, AP-3

Blood ◽  
1985 ◽  
Vol 65 (1) ◽  
pp. 227-232 ◽  
Author(s):  
PJ Newman ◽  
RW Allen ◽  
RA Kahn ◽  
TJ Kunicki
Keyword(s):  
Monoclonal Antibody ◽  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Human Platelets ◽  
Membrane Glycoprotein ◽  
Specific Monoclonal Antibody ◽  
A Value ◽  
Crossed Immunoelectrophoresis ◽  
Glycoprotein Iiia ◽  
Triton X

Abstract A murine monoclonal antibody specific for glycoprotein (GP)IIIa was prepared by immunization with a GPIIb- and GPIIIa-enriched Triton X-114 extract of platelet membranes. This antibody, designated AP-3, was shown by indirect immunoprecipitation to react solely with GPIIIa derived from either P1A1-positive or -negative individuals. The epitope on GPIIIa recognized by AP-3 is expressed on dissociated GPIIIa as well as on Ca+2-dependent complexes of GPIIb and GPIIIa, as shown by crossed immunoelectrophoresis in the presence or absence of EDTA. A previously described monoclonal antibody specific for the GPIIb/IIIa complex (AP- 2) inhibited platelet aggregation induced by ADP, thrombin, collagen, or arachidonic acid (Pidard et al, J Biol Chem 258:12582–12586, 1983). In contrast, AP-3 had no effect on aggregation induced by any of these reagents, a finding similar to that previously reported for the GPIIb- specific monoclonal antibody, Tab (McEver et al, J Clin Invest 66:1311- 1318, 1980). At saturation, 40,200 AP-3 molecules were bound per platelet, a value similar to that obtained for AP-2 or Tab. Thus, data derived using AP-3 indicate that significant amounts of free GPIIIa are not present, thereby supporting the hypothesis that GPIIb and GPIIIa exist complexed in a 1:1 stoichiometry in the plasma membrane of intact, nonactivated platelets.

scholarly journals Quantitation of membrane glycoprotein IIIa on intact human platelets using the monoclonal antibody, AP-3

Blood ◽  
1985 ◽  
Vol 65 (1) ◽  
pp. 227-232 ◽  
Author(s):  
PJ Newman ◽  
RW Allen ◽  
RA Kahn ◽  
TJ Kunicki
Keyword(s):  
Monoclonal Antibody ◽  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Human Platelets ◽  
Membrane Glycoprotein ◽  
Specific Monoclonal Antibody ◽  
A Value ◽  
Crossed Immunoelectrophoresis ◽  
Glycoprotein Iiia ◽  
Triton X

A murine monoclonal antibody specific for glycoprotein (GP)IIIa was prepared by immunization with a GPIIb- and GPIIIa-enriched Triton X-114 extract of platelet membranes. This antibody, designated AP-3, was shown by indirect immunoprecipitation to react solely with GPIIIa derived from either P1A1-positive or -negative individuals. The epitope on GPIIIa recognized by AP-3 is expressed on dissociated GPIIIa as well as on Ca+2-dependent complexes of GPIIb and GPIIIa, as shown by crossed immunoelectrophoresis in the presence or absence of EDTA. A previously described monoclonal antibody specific for the GPIIb/IIIa complex (AP- 2) inhibited platelet aggregation induced by ADP, thrombin, collagen, or arachidonic acid (Pidard et al, J Biol Chem 258:12582–12586, 1983). In contrast, AP-3 had no effect on aggregation induced by any of these reagents, a finding similar to that previously reported for the GPIIb- specific monoclonal antibody, Tab (McEver et al, J Clin Invest 66:1311- 1318, 1980). At saturation, 40,200 AP-3 molecules were bound per platelet, a value similar to that obtained for AP-2 or Tab. Thus, data derived using AP-3 indicate that significant amounts of free GPIIIa are not present, thereby supporting the hypothesis that GPIIb and GPIIIa exist complexed in a 1:1 stoichiometry in the plasma membrane of intact, nonactivated platelets.

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