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Biomedical subjects

M B Pepys

Publications and source records attributed to M B Pepys.

At least 91 records · Page 5Linked to original sources
PubMed1996

Three dimensional structure of human C-reactive protein.

The structure of the classical acute phase reactant human C-reactive protein provides evidence that phosphocholine binding is mediated through calcium and a hydrophobic pocket centred on Phe 66. The residue Glu 81 is suitably positioned to interact with the choline group. A cleft on the pentameric face opposite to that containing the calcium site may have an important functional role. The structure provides insights into the molecular mechanisms by which this highly conserved plasma protein, for which no polymorphism or deficiency state is known, may exert its biological role.

Amino Acid Sequence↗
PubMed1996

Primary localised amyloidosis of the orbit.

AIMS/BACKGROUND: Primary localised amyloidosis is rarely encountered in the orbit. The typical clinical and radiological appearances have not been clearly established, in particular the single site deposition of amyloid has never been proved. METHODS: Six cases were reviewed in detail and their clinical and radiological characteristics are described here. Four patients had scintigraphy with 123I serum amyloid P component and one patient had typing of the amyloid fibrils. RESULTS: All the patients had a firm mass in the upper orbit with a predilection for the region of the lacrimal gland. Computed tomography showed a homogeneous mass with thickening and irregularity of the adjacent bone and/or calcification within the mass. None was associated with systemic disease. Scintigraphy with 123I serum amyloid P component demonstrated that the amyloid was confined to the orbit. In one patient the amyloid fibrils were derived from an IgG4 heavy chain constant domain. The lesions were partially excised with subsequent clinical stability over 6 months to 18 years in all but one patient who had continued enlargement of the lesion. CONCLUSION: There is a characteristic clinical and radiological pattern for primary localised amyloidosis of the orbit. The disease process is truly local and not part of a systemic process. A majority respond to simple debulking with subsequent observation.

Adult↗
PubMed1995

Serum amyloid P component prevents proteolysis of the amyloid fibrils of Alzheimer disease and systemic amyloidosis.

Extracellular deposition of amyloid fibrils is responsible for the pathology in the systemic amyloidoses and probably also in Alzheimer disease [Haass, C. & Selkoe, D. J. (1993) Cell 75, 1039-1042] and type II diabetes mellitus [Lorenzo, A., Razzaboni, B., Weir, G. C. & Yankner, B. A. (1994) Nature (London) 368, 756-760]. The fibrils themselves are relatively resistant to proteolysis in vitro but amyloid deposits do regress in vivo, usually with clinical benefit, if new amyloid fibril formation can be halted. Serum amyloid P component (SAP) binds to all types of amyloid fibrils and is a universal constituent of amyloid deposits, including the plaques, amorphous amyloid beta protein deposits and neurofibrillary tangles of Alzheimer disease [Coria, F., Castano, E., Prelli, F., Larrondo-Lillo, M., van Duinen, S., Shelanski, M. L. & Frangione, B. (1988) Lab. Invest. 58, 454-458; Duong, T., Pommier, E. C. & Scheibel, A. B. (1989) Acta Neuropathol. 78, 429-437]. Here we show that SAP prevents proteolysis of the amyloid fibrils of Alzheimer disease, of systemic amyloid A amyloidosis and of systemic monoclonal light chain amyloidosis and may thereby contribute to their persistence in vivo. SAP is not an enzyme inhibitor and is protective only when bound to the fibrils. Interference with binding of SAP to amyloid fibrils in vivo is thus an attractive therapeutic objective, achievement of which should promote regression of the deposits.

Alzheimer Disease↗
PubMed1995

A novel variant of transthyretin, 59Thr-->Lys, associated with autosomal dominant cardiac amyloidosis in an Italian family.

BACKGROUND: Amyloidosis is a disorder of protein metabolism characterized by extracellular accumulation of abnormal protein fibrils. Different proteins form the fibrils in different forms of the disease, and the condition can be acquired or hereditary. Involvement of the heart is quite common, producing a serious and usually fatal cardiomyopathy. Cardiac amyloidosis is often diagnosed late, and cardiac biopsy together with proper histological examination is essential. Contrary to previous perceptions, there is much recent evidence of effective treatment for several different types of systemic and cardiac amyloidosis, including the most common hereditary form caused by mutations in the transthyretin gene. Chemical and genetic typing of amyloid is therefore of considerable clinical importance. METHODS AND RESULTS: Seven members in two generations of an Italian family presented with cardiac disease inherited as an autosomal dominant and were found to have systemic amyloidosis. Angina pectoris-like pain, an unusual feature in cardiac amyloidosis, was a prominent symptom, possibly related to partial obliteration of the distal coronary arteries by amyloid infiltration. There were also cases of sudden cardiac death. Peripheral and autonomic neuropathy, which are the usual features of hereditary amyloidosis, were present in only two cases, and a diagnosis of acquired, immunoglobulin light chain (AL type) amyloidosis was suspected in the index case before the family history emerged. In fact, the amyloid fibrils were composed of transthyretin, and the two affected individuals from whom DNA was available were both heterozygotes for a single base change in exon 3 of the transthyretin gene, encoding substitution of Lys for the wild-type Thr residue at position 59 in the mature protein. This mutation has not previously been reported. CONCLUSIONS: We have identified a novel mutation in the transthyretin gene encoding 59Thr-->Lys associated with autosomal dominant hereditary systemic amyloidosis in an Italian kindred in whom cardiac involvement was the major feature. This family illustrates the difficulty in diagnosis of cardiac amyloid, the variable clinical phenotype in hereditary amyloidosis even within a family, and the importance of precise fibril typing for correct management in this condition.

Amyloidosis↗
PubMed1995

Tolerance and immunity to the inducible self antigen C-reactive protein in transgenic mice.

The understanding of immunological tolerance has been greatly aided by the development of transgenic animal models in which expression of a specific T cell receptor (or B cell receptor) and its cognate self antigen is experimentally controlled. In most cases, expression of the self antigen was constitutive and did not allow for variation of its time- and dose-dependent expression pattern, parameters which are known to influence the balance of tolerance versus immunity. We describe a transgenic model in which expression of human C-reactive protein (hCRP), an acute-phase protein, is tightly controlled at basal levels (female mice express around 10(-9) M and male mice 5 x 10(-7) M circulating hCRP) and is highly inducible (induction factor of 25-500). T cells from C57BL/6 mice recognize two epitopes of hCRP termed A (residues 79-95) and B (residues 87-102). Different efficacies of presentation in vitro and in vivo identify epitope A as sub-dominant and epitope B as dominant. T cells of non-induced hCRP transgenic mice are tolerant to the dominant epitope, but reactive to the subdominant epitope. A hCRP-specific IgG antibody response is detectable in transgenic mice, but is weaker than in littermates. Upon induction of hCRP, both T cell epitopes are presented by thymic and splenic antigen-presenting cells (APC) in vivo. Kinetics of presentation by splenic APC closely match serum kinetics of hCRP, whereas presentation in the thymus is considerably prolonged. This model enables epitope-specific T cell tolerance to be studied as a function of time- and dose-dependent expression of the self antigen.

Amino Acid Sequence↗
PubMed1995

Treatment of amyloidosis.

Amyloidosis is the extracellular deposition of normally soluble autologous protein in a characteristic abnormal fibrillar form. Systemic amyloidosis and some local forms are progressive, cause major morbidity, and are often fatal. No treatment specifically causes the resolution of amyloid deposits, but therapy that reduces the supply of amyloid fibril precursor proteins can improve survival and preserve organ function. Major regression of amyloid occurs in at least a proportion of such cases, suggesting that the clinical improvement reflects mobilization of amyloid. The clearest evidence for regression of amyloid has been obtained in juvenile rheumatoid arthritis patients with AA amyloidosis treated with chlorambucil. This drug suppresses the acute phase production of serum amyloid A protein, the precursor of AA amyloid fibrils, and is associated with remission of proteinuria and greatly improved survival. In many such patients, scintigraphy with serum amyloid P component shows major regression of amyloid over 12 to 36 months and frequently reveals a discrepancy between the local amyloid load and organ dysfunction. Measurement of target organ function is therefore not an adequate method for monitoring treatment aimed at promoting the resolution of amyloid. In monoclonal immunoglobulin light chain (AL) amyloidosis the aim of treatment is to suppress the underlying B-cell clone and, therefore, production of the amyloid fibril precursor protein. This can be difficult to achieve or sustain and, since the prognosis is so poor, many patients die before benefits of therapy are realized. A recent development has been the introduction of liver transplantation as treatment for familial amyloid polyneuropathy caused by transthyretin gene mutations. This leads to the disappearance of variant transthyretin from the plasma and halts progression of the neurologic disease. Features of autonomic neuropathy frequently ameliorate, and improvement in peripheral motor nerve function has been recently reported. Serum amyloid P component scans show regression of associated visceral amyloidosis. This surgical form of gene therapy holds much promise for patients with familial amyloid polyneuropathy and has been widely adopted. The only other form of amyloidosis in which the supply of the fibril precursor protein can be sharply reduced is beta 2M amyloidosis in long-term hemodialysis patients. Renal transplantation lowers the plasma concentration of beta 2M to normal levels and is associated with rapid improvement of the osteoarticular symptoms. Preliminary observations suggest that the beta 2M amyloid deposits also can regress in some patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Amyloidosis↗
PubMed1995

Transthyretin gene analysis in European patients with suspected familial amyloid polyneuropathy.

We investigated 99 patients from 64 European families (51 French, 11 British, one Italian and one Spanish) with suspected familial amyloid polyneuropathy (FAP) for transthyretin (TTR) gene mutations. Thirty-nine families were found to have point mutations causing the following amino acid substitutions: Met30 (28 families), Tyr77 (five), Arg 50 (one), Ala49 (one), Gln89 (one), Ala60 (one) and one each with previously undescribed mutations at Asn35 and Gys54. The clinical picture in the patients with new and known mutations were typical of FAP, without any specific features for a particular mutation. Onset of symptoms was late (over 50 years) in many French and British patients with the Met30 and Tyr77 mutations, and only 30% of all index cases had affected relatives. We propose an approach to molecular diagnosis in European patients with FAP, apart from members of families with known mutations, based on the frequency of TTR mutations observed in this and and other studies of FAP in Europe. It is logical to screen for the Met30 and Tyr77 mutations and Ala60 in the UK, using restriction enzyme analysis. If these are absent, the TTR gene should be sequenced directly to detect less common or unknown mutations.

Adult↗
PubMed1994

Comparative analyses of pentraxins: implications for protomer assembly and ligand binding.

BACKGROUND: Pentraxins are a family of plasma proteins characterized by their pentameric assembly and calcium-dependent ligand binding. The recent determination of the crystal structure for a member of this family, human serum amyloid P component (SAP), provides a basis for the comparative analysis of the pentraxin family. RESULTS: We have compared the sequences, tertiary structures and quaternary arrangements of SAP with human C-reactive protein (CRP), Syrian hamster SAP (HSAP) and Limulus polyphemus CRP (LIM). These proteins can adopt a beta-jelly roll topology and a hydrophobic core similar to that seen in SAP. Only minor differences are observed in the positions of residues involved in coordinating calcium ions. CONCLUSIONS: Calcium-mediated ligand binding by CRP, HSAP and LIM is similar to that defined by the crystal structure of SAP, but sequence differences in the hydrophobic pocket explain the differential ligand specificities exhibited by the homologous proteins. Differences elsewhere, including insertions and deletions, account for the different (hexameric) quaternary structure of LIM.

Amino Acid Sequence↗
PubMed1994

The prognostic value of C-reactive protein and serum amyloid a protein in severe unstable angina.

BACKGROUND: The pathogenesis of unstable angina is poorly understood, and predicting the prognosis at the time of hospital admission is problematic. Recent evidence suggests that there may be active inflammation, possibly in the coronary arteries, in this syndrome. We therefore studied the prognostic value of measurements of the circulating acute-phase reactants C-reactive protein and serum amyloid A protein, which are sensitive indicators of inflammation. METHODS: We measured C-reactive protein, serum amyloid A protein, creatine kinase, and cardiac troponin T in 32 patients with chronic stable angina, 31 patients with severe unstable angina, and 29 patients with acute myocardial infarction. RESULTS: At the time of hospital admission, creatine kinase and cardiac troponin T levels were normal in all the patients, but the levels of C-reactive protein and serum amyloid A protein were > or = 0.3 mg per deciliter (exceeding the 90th percentile of the normal distribution) in 4 of the patients with stable angina (13 percent), 20 of the patients with unstable angina (65 percent), and 22 of the patients with acute myocardial infarction (76 percent). The 20 patients with unstable angina who had levels of C-reactive protein and serum amyloid A protein > or = 0.3 mg per deciliter had more ischemic episodes in the hospital than those with levels < 0.3 mg per deciliter (mean [+/- SD] number of episodes per patient, 4.8 +/- 2.5 vs. 1.8 +/- 2.4; P = 0.004); 5 patients subsequently had a myocardial infarction, 2 died, and 12 required immediate coronary revascularization. In contrast, no deaths or myocardial infarction occurred among the 11 patients with levels of C-reactive protein and serum amyloid A protein < 0.3 mg per deciliter, and only 2 of them required coronary revascularization. Among the patients admitted with a diagnosis of acute myocardial infarction, unstable angina preceded infarction in 14 of the 22 patients (64 percent) with levels of C-reactive protein and serum amyloid A protein > or = 0.3 mg per deciliter but in none of the 7 patients with levels < 0.3 mg per deciliter. CONCLUSIONS: Elevation of the sensitive acute-phase proteins C-reactive protein and serum amyloid A protein at the time of hospital admission predicts a poor outcome in patients with unstable angina and may reflect an important inflammatory component in the pathogenesis of this condition.

Angina Pectoris↗
PubMed1994

Concentration of serum amyloid P component in the CSF as a possible marker of cerebral amyloid deposits in Alzheimer's disease.

Serum amyloid P component (SAP) is a normal plasma protein produced in the liver and co-deposited with amyloid fibrils in all types of amyloidosis, including cerebral beta-protein amyloid deposits associated with Alzheimer's disease (AD). We have measured its concentration and those of alpha 2-macroglobulin, IgG and albumin in the CSF of 51 patients with AD and 50 healthy and disease control subjects. The mean levels of SAP were 12.8 ng/ml in AD and 8.5 ng/ml in controls (P < 0.0125); there was no difference in the levels of the other proteins studied. The observed concentrations of SAP were much lower than expected for a protein of molecular weight 254620. The difference between AD and controls suggests that the concentration of SAP in the CSF may be affected by the presence of cerebral amyloidosis.

Aged↗
PubMed1994

Human serum amyloid P component is an invariant constituent of amyloid deposits and has a uniquely homogeneous glycostructure.

Human serum amyloid P component (SAP) is a normal plasma protein and the precursor of amyloid P component (AP), a universal constituent of the abnormal tissue deposits in amyloidosis, including Alzheimer disease. We show here that its single N-linked biantennary oligosaccharide does not display the microheterogeneity usually characteristic of glycoproteins. The protein and the glycan structures of AP were also invariant, their resistance to degradation suggesting a role in persistence of amyloid deposits. Asialo-SAP was rapidly cleared from the circulation in mice by a mechanism dependent on terminal galactose residues and was catabolized in hepatocytes. However blockade of this pathway did not affect the clearance of native SAP. Rapid hepatic uptake and catabolism of human asialo-SAP in man were also directly demonstrated. The protein and glycan homogeneity of SAP and the integrity of AP suggest that the complete glycoprotein structure is important for the normal and the pathophysiological functions of this molecule.

Amyloid↗
PubMed1994

Structure of pentameric human serum amyloid P component.

The three-dimensional structure of pentameric human serum amyloid P component at high resolution, the first reported for a pentraxin, reveals that the tertiary fold is remarkably similar to that of the legume lectins. Carboxylate and phosphate compounds bind directly to two calcium ions; interactions with a carboxyethylidene ring are mediated by Asn 59 and Gln 148 ligands of the calcium ions. These X-ray results indicate the probable modes of binding of the biologically important ligands, DNA and amyloid fibrils.

Amino Acid Sequence↗
PubMed1994

Primary localized orbital amyloidosis composed of the immunoglobulin gamma heavy chain CH3 domain.

1. Primary orbital amyloidosis is a rare form of localized amyloidosis in which the precursor protein has not previously been identified. We report here the first extraction of amyloid fibrils from a tissue biopsy containing orbital amyloid, and characterization of the fibril protein. 2. The N-terminal nine residues were identical with residues 278-286 and 275-283 of the third constant (CH3) domains of IgG1 and IgG4 gamma heavy chains, respectively. The mass of the fibril subunit protein was 6125Da by time-of-flight mass spectrometry, compared with the expected masses of 6169.9Da and 6214.9Da for the CH3 domains of gamma 1 from residue 278 and gamma 4 from residue 275, respectively. The fibril protein thus appeared to consist exclusively of an immunoglobulin heavy chain constant domain. 3. Only two examples of immunoglobulin heavy chain derived amyloid have been reported previously and both of these, as well as all published cases of the usual immunoglobulin light chain derived amyloid, contained variable domain sequence. The present case therefore represents a form of local, presumably clonal, B-cell/plasma-cell disorder characterized uniquely by deposition of an amyloidogenic immunoglobulin heavy chain constant domain fragment.

Aged↗
PubMed1994

Binding of pentraxins to different nuclear structures: C-reactive protein binds to small nuclear ribonucleoprotein particles, serum amyloid P component binds to chromatin and nucleoli.

Binding of the human pentraxin plasma proteins, C-reactive protein (CRP) and serum amyloid P component (SAP), to the nuclei of human cells was studied using whole acute phase serum as the source of the proteins and confocal immunofluorescence microscopy. CRP and SAP clearly bound to distinct, different structures. Double staining with MoAbs to the Sm D and Sm B/B' components of small nuclear ribonucleoproteins confirmed that CRP bound exclusively to these particles. As expected, SAP bound to chromatin and, in addition, binding to the nucleolus was observed for the first time. These interactions demonstrated under relatively physiological conditions, with native pentraxins unseparated from serum and with nuclear constituents in situ, are likely to be of functional importance in vivo.

Animals↗