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M W Makgoba

Publications and source records attributed to M W Makgoba.

At least 19 recordsLinked to original sources
PubMed1997

The interaction of CGRP and adrenomedullin with a receptor expressed in the rat pulmonary vascular endothelium.

An abundant, seven trans-membrane domain receptor related to the calcitonin receptor has been studied by a number of groups without identification of its ligand. A recent report claimed that the receptor was a type 1 CGRP receptor (Aiyar et al J. Biol. Chem. 271 11325-11329 (1996)). We have studied the equivalent rat sequence in transfected cells. When expressed in 293 cells the receptor interacts with CGRP and adrenomedullin with KD values of 1.2 nM for CGRP and 11 nM for adrenomedullin. Both ligands cause an elevation of intracellular cAMP with EC50 values of 4 nM and 20 nM respectively and these effects are inhibited by the antagonist CGRP8-37. The receptor is expressed at high levels in the pulmonary vascular endothelium. Both the pharmacological data and the localisation are consistent with the conclusion that the orphan receptor is a type J CGRP receptor. However, when expressed in COS-7 cells, no receptor activity could be demonstrated suggesting that 293 cells contain a factor necessary for functional receptor expression.

Adrenomedullin↗
PubMed1993

Immunological similarity between the 170 kD amoebic adherence glycoprotein and human beta 2 integrins.

Amoebiasis is an important cause of morbidity and mortality in developing countries. Virulence of Entamoeba histolytica depends on the trophozoite's being able to bind to colonic epithelium; binding is mediated by the 170 kD subunit of a 260 kD lectin. We found, by microcytofluorometry and western blotting studies, that this 170 kD subunit protein shares an epitope with human beta 2 integrins--a subfamily of cell-surface glycoproteins expressed exclusively on leucocytes and involved in many adhesive and signalling interactions. The immunological similarity between these proteins may explain the trophozoite's ability to bind to and invade colonic epithelium.

Amebiasis↗
PubMed1992

Enhancement of epidermal growth factor (EGF) and insulin-stimulated tyrosine phosphorylation of endogenous substrates by sodium selenate.

Sodium selenate stimulated tyrosine phosphorylation of the epidermal growth factor (EGF) receptor in A431 cells and enhanced the tyrosine phosphorylation of endogenous proteins in response to EGF in A431 cells and insulin in NIH 3T3 HIR3.5 cells. These effects occurred without changes in ligand binding, were not abolished by mercaptoethanol in the case of the EGF receptor, and appeared distinct from the effects of vanadate. These results support a role for selenium or selenoproteins in regulating EGF and insulin receptor tyrosine kinase activity and suggest a mechanism whereby selenium-containing compounds contribute to cell growth.

3T3 Cells↗
PubMed1992

The expression and role in T cell adhesion of LFA-3 and ICAM-2 on human thyroid cells.

Thyroid follicular cells from patients with Graves' disease and Hashimoto's thyroiditis express intercellular adhesion molecule-1 (ICAM-1) and this is in part responsible for T cell adherence in vitro. To assess the potential role of other adhesion molecules in autoimmune thyroiditis, we investigated the expression and function of lymphocyte function-associated antigen-3 (LFA-3) and ICAM-2 on thyroid cells. Under basal culture conditions, a mean of 22.7% of Graves' thyroid cells (n = 8) expressed LFA-3 and this was enhanced by a mixture of T cell-derived cytokines and by IL-1, but not by TSH. LFA-3 was also demonstrated on Graves' (n = 4) and Hashimoto (n = 2) thyroid cells by immunohistochemical staining ex vivo. A small number of thyroid cells (mean 5.5%, n = 5) expressed ICAM-2 by flow cytometry but this was not altered by cytokines, and ICAM-2 could only be demonstrated on endothelial cells by immunohistochemical staining. It seems likely that contamination of primary thyroid cultures by such cells accounted for the small number of ICAM-2+ cells found using flow cytometry. Almost all of the cultured cells expressing LFA-3 or ICAM-2 also expressed ICAM-1, as assessed by dual staining. Blocking LFA-1, LFA-3, and ICAM-1 with monoclonal antibodies inhibited the adherence of T cells to thyroid follicular cells in assays of cell clustering; antibodies against ICAM-2 had no effect. These results show that two important adhesion receptor ligands, ICAM-1 and LFA-3, are expressed by thyroid cells in autoimmune thyroiditis and that these are likely to have functional importance in allowing T cells to bind to thyroid cell targets. This may play an important role in the initiation and maintenance of Graves' disease and Hashimoto's thyroiditis.

Antibodies, Monoclonal↗
PubMed1991

Circulating ICAM-1 isoforms: diagnostic prospects for inflammatory and immune disorders.

Intercellular adhesion molecule-1 (ICAM-1, CD54) is an important early marker of immune activation and response. Evidence on its role has come from immunohistological staining of tissues, since no free circulating ICAM-1 has been detected. By means of monoclonal antibodies against ICAM-1 and a sensitive chemiluminescence technique, free circulating ICAM-1 was detected in serum from sixteen healthy young volunteers. The concentrations varied among the subjects. Non-denaturing gel separation methods showed that ICAM-1 circulates in at least three isoforms, the proportions of which also varied. These findings have important implications for the investigation, diagnosis, and therapeutic monitoring of various inflammatory, neoplastic, and immune disorders.

Adult↗
PubMed1991

Molecular mechanisms of insulin resistance.

This review discusses recent advances in understanding of the structure and function of the insulin receptor and insulin action, and how these relate to the clinical aspects of insulin resistance associated with non-insulin-dependent diabetes and other disorders. Improved understanding of the molecular basis of insulin resistance could ultimately lead to a better understanding of the causation of these conditions and the design of rational therapy to ameliorate them. Here, particular attention is devoted to the initial events that follow the binding of insulin to its receptor, including changes in insulin receptor phosphorylation. Receptor-mediated insulin resistance may be a consequence of various factors including increased serine/threonine phosphorylation of the receptor with decreased tyrosine phosphorylation, receptor desensitization, auto-antibodies to the receptor and inherited structural defects in the insulin receptor. Defects in insulin action could also arise at post-receptor events particularly glucose transport. Other circulating hormones, such as the newly characterised islet amyloid polypeptide (amylin), may also cause insulin resistance.

Diabetes Mellitus, Type 2↗
PubMed1991

ICAM-2 peptides mediate lymphocyte adhesion by binding to CD11a/CD18 and CD49d/CD29 integrins.

Three fifteen-amino-acid polypeptides designated peptides 1, 2 and 3 were synthesised as likely candidates for mimicking the role of ICAM-2 as a ligand. The ability of each peptide to bind lymphoid cells was tested. Peptide 2 largely mediated cell attachment of unstimulated cells and this binding was only marginally increased by stimulating the cells with phorbol dibutyrate (P(Bu)2). Peptide 3 mediated minimal spontaneous cell attachment, but this binding was significantly enhanced following P(Bu)2 stimulation. Peptide 1 had no effect on cell attachment with or without stimulation. The cell attachment to peptide 2 was both temperature- and cation-dependent. Studies using specific monoclonal antibodies showed that with unstimulated cells, anti-VLA-4 alpha(CD49d) or beta chain (CD29) antibodies (KD4-13 and 4B4) and anti-CD18 (1B4) each partially inhibited the cell binding. Monoclonal antibodies against CD54 (ICAM-1; 84H10 or LB2), MHC class 1 (W6/32) and control mouse IgG had no effect. When anti-CD29 and anti-CD18 monoclonal antibodies were used concurrently, there was almost complete inhibition of the cell attachment. These observations indicated that cell adhesion via ICAM-2 is mediated: (i) predominantly by peptide 2 in unstimulated and P(Bu)2-stimulated cells, and also, to some extent, by peptide 3 in P(Bu)2-stimulated cells and (ii) by binding to both CD11/CD18 and CD49d/CD29 integrins.

Amino Acid Sequence↗
PubMed1990

Functional analysis of intercellular adhesion molecule-1-expressing human thyroid cells.

We have tested the potential role of thyroid cell intercellular adhesion molecule-1 (ICAM-1) expression by in vitro assays of cell clustering and cytotoxicity. Increased ICAM-1 appeared within 24 h of thyroid cell stimulation with cytokines and was not inhibited by the antithyroid drug methimazole. Autologous and allogeneic lymphocyte-thyroid cell cluster formation, assessed by flow cytometry, was reduced by about one-third in the presence of a monoclonal antibody against ICAM-1, regardless of whether thyroid cells were expressing basal levels of ICAM-1 or had been stimulated with interferon-gamma. The cytotoxicity produced by interleukin 2-stimulated allogeneic lymphocytes was not consistently inhibited by anti-ICAM-1 antibody, but phytohemagglutinin-stimulated lymphocytes showed a reduction of 23%-28% in cytotoxicity against untreated or interferon-gamma stimulated thyroid cells when the anti-ICAM-1 monoclonal antibody was present. Finally, thyroid cells could be infected by rhinovirus, confirming the presence of fully functional ligand. These results show that ICAM-1 expression by thyroid cells may enhance immune cell recognition and play some role in cytotoxicity, features which could be important in the initiation or perpetuation of autoimmune thyroiditis.

Cell Adhesion↗
PubMed1990

Differential upregulation of intercellular adhesion molecule-1 in coeliac disease.

The expression of intercellular adhesion molecule-1 (ICAM-1) was studied on peroral jejunal biopsies from patients with coeliac disease. The biopsies from untreated patients exhibited greater staining of the superficial lamina propria cells compared with treated patients and controls. A gluten challenge in treated patients produced an altered staining pattern within 2 h. The results demonstrate the role of ICAM-1 expression in coeliac disease, providing further evidence for the role of lamina propria cells in the pathogenesis of this condition.

Antigens, CD↗