Papers by Maurice Hallett
Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2020
Neutrophils exhibit rapid cell spreading and phagocytosis, both requiring a large apparent increa... more Neutrophils exhibit rapid cell spreading and phagocytosis, both requiring a large apparent increase in the cell surface area. The wrinkled surface topography of these cells may provide the membrane reservoir for this. Here, the effects of manipulation of the neutrophil cell surface topography on phagocytosis and cell spreading were established. Chemical expansion of the plasma membrane or osmotic swelling had no effects. However, osmotic shrinking of neutrophils inhibited both cell spreading and phagocytosis. Triggering a Ca 2+ signal in osmotically shrunk cells (by IP3 uncaging) evoked tubular blebs instead of full cell spreading. Phagocytosis was halted at the phagocytic cup stage by osmotic shrinking induced after the phagocytic Ca 2+ signalling. Restoration of isotonicity was able to restore complete phagocytosis. These data thus provide evidence that the wrinkled neutrophil surface topography provides the membrane reservoir to increase the available cell surface area for phagocytosis and spreading by neutrophils.
Biochemical Society Transactions, 2000
Optical Methods for the Measurement and Manipulation of Cytosolic Calcium Signals in Neutrophils
Humana Press eBooks, 2014
The measurement and manipulation of cytosolic free Ca(2+) of neutrophils is crucial for investiga... more The measurement and manipulation of cytosolic free Ca(2+) of neutrophils is crucial for investigating the mechanisms within living neutrophils which generate Ca(2+) signals and the cellular responses triggered by them. Optical methods for this are the most applicable for neutrophils and are discussed here, especially the use of fluorescent indicators of Ca(2+) and photoactivation of reagents involved in Ca(2+) signaling. Both of these synthetic agents can be loaded into neutrophils as lipid-soluble esters or can be microinjected into the cell. In this chapter, we will outline some of the techniques that have been used to monitor, visualize, and manipulate Ca(2+) in neutrophils.
Biochemical Society Transactions, Apr 1, 1981
Applications of coelenterate luminescent protein
Marcel Dekker eBooks, 1982
Measurement of intracellular free calcium: Importance during activation and injury of small cells
Raven Press eBooks, 1985
Biochemical Society Transactions, Dec 1, 1985
Biochemical Society Transactions, Aug 1, 1998
Cystic fibrosis (CF) is a common lethal inherited disease of Caucasians, with a carrier frequency... more Cystic fibrosis (CF) is a common lethal inherited disease of Caucasians, with a carrier frequency of 1 in 25 in the U.K. It is characterised by viscous mucous secretions in the pancreatic ducts and lungs, leading to pancreatic malhnction and chronic lung disease. The CF gene protein, the CF transmembrane conductance regulator (CFTR) is a membrane protein which acts as a cyclic AMP dependent Cf channel [I]. Our studies [2-41,
Biochemical Society Transactions, 1981
Cytoplasmic free calcium: measurement and manipulation in living cells
IRL Press eBooks, 1990
Increased production of oxygen radicals by circulating monocytes in inflammatory bowel-disease evidence of activation
Biochemical Society Transactions, Feb 1, 1982
Inhibition of HGF/SF-induced tumor-cell membrane ruffling by calcium signalling
Luminescence in cells and vesicles isolated from the hydroid Obelia geniculata [proceedings]
PubMed, Feb 1, 1979
Journal of Structural Biology, Sep 1, 2014
Excessive activity of neutrophils has been linked to many pathological conditions, including rheu... more Excessive activity of neutrophils has been linked to many pathological conditions, including rheumatoid arthritis, cancer and Alzheimer's disease. Calpain-I is a Ca 2+-dependent protease that plays a key role in the extravasation of neutrophils from the blood stream prior to causing damage within affected tissues. Inhibition of calpain-I with small molecule mercaptoacrylic acid derivatives slows the cell spreading process of live neutrophils and so these compounds represent promising drug leads. Here we present the 2.05 and 2.03 Å co-crystal X-ray structures of the pentaEF hand region, PEF(S), from human calpain with (Z)-3-(4-chlorophenyl)-2-mercaptoacrylic acid and (Z)-3-(5-bromoindol-3-yl)-2-mercaptoacrylic acid. In both structures, the amercaptoacrylic acid derivatives bind between two a-helices in a hydrophobic pocket that is also exploited by a leucine residue of the endogenous regulatory calpain inhibitor calpast-atin. Hydrophobic interactions between the aromatic rings of both inhibitors and the aliphatic residues of the pocket are integral for tight binding. In the case of (Z)-3-(5-bromoindol-3-yl)-2-mercaptoacrylic acid, hydrogen bonds form between the mercaptoacrylic acid substituent lying outside the pocket and the protein and the carboxylate group is coplanar with the aromatic ring system. Multiple conformations of (Z)-3-(5-bromoindol-3-yl)-2-mercaptoacrylic acid were found within the pocket. The increased potency of (Z)-3-(5-bromoindol-3-yl)-2mercaptoacrylic acid relative to (Z)-3-(4-chlorophenyl)-2-mercaptoacrylic acid may be a consequence of the indole group binding more deeply in the hydrophobic pocket of PEF(S) than the phenyl ring.
Human calpain PEF(S) with (2Z,2Z')-2,2'-disulfanediylbis(3-(6-bromoindol-3-yl)acrylic acid) bound
β-adrenergic mobilization of Ca2+ from an intracellular store in rat submandibular acini
Biochemical Journal, Aug 1, 1993
Biochemical Society Transactions, Aug 1, 1985
Luminol-enhanced chemiluminescence demonstrated that 2-chloroadenosine inhibited complement-induc... more Luminol-enhanced chemiluminescence demonstrated that 2-chloroadenosine inhibited complement-induced reactive oxygen metabolite production in human polymorphonuclear leucocytes. ,2$his inhibition was reversed by B-phenyltheophylline. Binding of a [ I]-labelled monoclonal antibody against Cg to human PMN demonstrated removal of membrane attack complexes from the cell membranes, and in addition indicated inhibition of this process by 2-chloroadenosine. This compound also increased the percentage of complement-induced cell lysis of polymorphonuclear leucocytes.
Phagocytosis and Motility in Human Neutrophils is Competent but Compromised by Pharmacological Inhibition of Ezrin Phosphorylation
Current Molecular Pharmacology, Oct 5, 2018
BACKGROUND AND OBJECTIVE Ezrin links the cortical cytoskeleton to the plasma membrane and plays a... more BACKGROUND AND OBJECTIVE Ezrin links the cortical cytoskeleton to the plasma membrane and plays a role in regulating changes in cell shape. Recently, NSC668394 has been shown to inhibit a key step for its activity, i.e. phosphorylation at threonine 567. In neutrophils, another key regulatory step is the Ca2+-mediated cleavage of ezrin by calpain. METHODS In this paper, we use NSC668394 as a pharmacological inhibitor to investigate the interplay between these two steps in regulating changes in neutrophil shape. RESULTS NSC668394 reduced the amount of peripherally located ezrin in neutrophils, and increased Ca2+-dependent ezrin cleavage. Neutrophils with NSC668394-inhibited ezrin phosphorylation remained both phagocytic and chemotactically competent. However, phagocytosis was slightly impaired and chemotaxis could not be maintained over longer periods. The characteristic chemotactic morphology which neutrophils adopt was also aberrant. Although phosphorylation of ezrin plays a minor role in limiting the rapid changes in cell shape in neutrophils, inhibition of ezrin phosphorylation by NSC668394 prevented multiple and prolonged shape changes during extended chemotaxis. CONCLUSION The susceptibility of prolonged chemotaxis to inhibition by NSC668394 may point to a useful target for anti-inflammatory therapy. Inhibition of neutrophil chemotaxis towards chronically inflamed sites without compromising their ability to undergo phagocytosis is a much sought after the effect of anti-neutrophil therapy.
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Papers by Maurice Hallett