Biomedical subjects
Publications and source records attributed to P Westermark.
Deposition of amyloid in the atria is exceedingly common in the aging heart. We have extracted amyloid fibrils from atria and purified a major protein which had N-terminal amino acid sequence identical to that of atrial natriuretic peptide (ANP). Antisera to ANP and to the amyloid fibril protein both labelled atrial muscle cells and atrial amyloid in an identical way.
A novel peptide, islet amyloid polypeptide (IAPP), with structural resemblance to calcitonin gene-related peptide has recently been purified from amyloid deposits in an insulinoma and from islets of Langerhans. By immunohistochemical methods, using antisera to a synthetic undecapeptide of IAPP and to insulin, we show that freshly fixed islet B cells in man, guinea pig, rat, mouse and hamster exhibit strong IAPP-immunoreactivity while A cells are unreactive. In human autopsy material, all of 11 non-diabetic individuals had IAPP immunoreactivity of the islets. In comparison 8 of the 13 patients with Type 2 (non-insulin-dependent) diabetes had no IAPP immunoreactive cells. The proportion of islet cells having IAPP immunoreactivity exceeded 10% in only 1 of the 5 remaining diabetic patients while in all 13 patients substantially more than 10% of the islet cells contained immunoreactive insulin. IAPP-positive amyloid deposits were found in 20-99% of the islets in 12 of the Type 2 diabetic patients while 6 of 11 non-diabetic subjects had amyloid in 3-11% of their islets. In islets with IAPP-immunoreactive amyloid, very few IAPP-cells were seen despite a strong reaction of the B cells with antiserum to insulin. This study shows that IAPP is a normal islet B cell component and that IAPP immunoreactivity in B cells is diminished in Type 2 diabetes while IAPP is deposited as amyloid fibrils in the islets of Langerhans. Although the function of IAPP is unknown, its occurrence in the islet B cells and its structural relation to calcitonin gene-related peptide makes a hormonal nature probable.(ABSTRACT TRUNCATED AT 250 WORDS)
Amyloid deposits localized to the islets of Langerhans are typical of non-insulin-dependent human diabetes mellitus and of diabetes mellitus in adult cats. Amyloid deposits also commonly occur in insulin-producing pancreatic tumors. We have purified a major protein--insulinoma or islet amyloid polypeptide (IAPP)--from human and cat islet amyloid and from amyloid of a human insulinoma. IAPP from human insulinoma contained 37 amino acid residues and had a theoretical molecular mass of 3850 Da. The amino acid sequence is unique but has greater than 40% identity with the human calcitonin gene-related peptide. A partial amino acid sequence of cat islet IAPP corresponding to positions 1-27 of human insulinoma IAPP was identical to the human IAPP except for substitutions in three positions. An antiserum raised to a synthetic human insulinoma IAPP-(7-17) undecapeptide showed specific immunohistochemical reactivity with human and cat islet amyloid and with islet B cells. The significance of this pancreatic neuropeptide-like protein is unknown, but it is suggested that it may exert an important endocrine regulatory effect.
In recent years prealbumin has been shown to be a major component of two forms of systemic amyloid, senile systemic amyloid (SSA), and familial amyloidotic polyneuropathy (FAP). Despite the fact that the amyloid fibril proteins associated with these two forms of amyloid, designated ASc1 and AF, respectively, share many similarities the clinical features of the two diseases are remarkably different. To understand better this paradox the clinical, histochemical, immunological and biochemical features of SSA and FAP were reviewed.
Amino-acid sequence analysis of an amyloid fibril protein from a patient with Swedish familial amyloidotic polyneuropathy showed homology with prealbumin but with heterogeneous N-terminal deletions. One-third of the molecules had the same amino acid substitution, methionine for valine in position 30, as in familial amyloidosis of Portuguese, Japanese and Swedish-American type. A protein with the same antigenic properties and size was found in the fibrils of two other patients with Swedish FAP while the amyloid fibrils in two further patients predominantly contained a smaller prealbumin-derived protein. Cyanogen bromide cleavage of this protein revealed no evidence for a methionine residue in position 30.
Amyloid deposition is a very typical alteration in the islets of Langerhans in human Type 2 (non-insulin-dependent) diabetes mellitus and in feline diabetes mellitus. Amyloid infiltration is also commonly found in insulin-producing pancreatic tumors. It was shown recently that amyloid purified from an insulinoma was composed mainly of a novel polypeptide (insulinoma amyloid polypeptide, IAPP), which had partial identity with the neuropeptide calcitonin gene-related peptide (CGRP). Cat islet amyloid contained a similar polypeptide. This finding is verified in the present study, and it is shown that the cat IAPP differs from the human peptide only in two of the 16 elucidated amino acid residues. The authors now also show by N-terminal amino acid sequence analysis that human islet amyloid is of IAPP origin. Although the significance of IAPP is unknown, its occurrence in pancreatic endocrine tissue and partial identity with a known neuropeptide suggests an endocrine regulatory function.
Protein AA, the main fibril protein in secondary systemic amyloidosis, is a mixture of protein fragments (subspecies) of different length, probably arising by enzymatic cleavage of a serum precursor, SAA. We have purified amyloid fibril protein AA from a patient with rheumatoid arthritis and secondary amyloidosis with an unusual amyloid distribution in organs. This protein AA contained two major subspecies of which one consisted of 50 amino acid residues shown by complete amino acid sequence analysis. The other major AA subspecies, characterized by N- and C-terminal sequence analysis and amino acid determination of proteolytic peptides, contained 45 amino acid residues. The pI of these AA-variants differed considerably, 8.1 to 5.5, respectively. Several minor protein AA subspecies were also identified, among them one with a blocked N-terminal. The findings indicate that AA proteins of different length are connected to varying AA amyloid syndromes.
Deposition of amyloid is the most constantly present alteration in the islets of Langerhans in type 2 diabetes mellitus and is also quite common in insulin-producing tumors of the pancreas and it is very likely that these two amyloids are identical. We have isolated amyloid fibrils from an insulin-secreting human tumour and purified the fibrillar protein. N-terminal amino acid sequence of the protein is unique and does not resemble insulin or its precursors. Instead it has about 50% homology with the neuropeptide CGRP (calcitonin gene related peptide).
In lichen amyloidosus (LA) and macular amyloidosis (MA), small amyloid deposits occur in the upper papillary dermis. Previous electron-microscopic studies have indicated an epidermal origin of the amyloid, where degenerating keratinocytes drop into the dermis and undergo transformation to amyloid. While this mechanism seems possible at least in MA, we suggest an alternative pathogenetic pathway in LA, in which amyloid fibrils seem to form on the dermal surface of living basal keratinocytes. It is possible that the different morphology of the amyloid in LA and MA is explained by partially different pathogenetic mechanisms although the amyloid in both conditions may be chemically closely related.
Amyloid-laden renal glomeruli were selectively isolated from a cow with a history of multiple organ inflammatory diseases which terminated in amyloid-induced glomerulopathy and severe proteinuria. Lyophilized amyloid fibrils obtained by water extraction procedures were dissolved in 6M guanidine hydrochloride and gel filtered on Sepharose CL6B and Sephacryl S-300 Superfine columns for slab gel electrophoresis, analytic isoelectric focusing, and amino acid sequence analyses. Electrophoresis of material from the major retarded peak of the elution profile revealed that bovine protein AA moves as one band with an apparent molecular mass of about 14,000 Daltons. Several distinct bands between approximately pH 4.0 and 5.0 were observed when this material was evaluated by analytic isoelectric focusing, thus having a pattern resembling that of human and dog protein AA. A blocked N-terminus was demonstrated when protein from the major retarded peak was subjected to amino acid sequencing, but cyanogen bromide cleavage followed by gel filtration produced 3 peptide fragments for amino acid sequence analysis. These peptides had a high degree of homology with positions 4-14, 18-24 and 25-49 of human protein AA. An apparent complete homology between bovine protein AA and protein AA from other species was apparent at positions 35-45, providing further evidence that this is a functionally significant part of the serum protein AA (SAA) molecule.
Amyloid fibrils were isolated from the vitreous of 9 patients with familial amyloidosis. The material of all patients contained proteins reacting in double immunodiffusion with an antiserum against an amyloid protein which previously has been shown to be prealbumin-related. Two out of five tested vitreous amyloid materials also showed a reaction of identity with antihuman prealbumin. It was shown by electrophoresis that the amyloid subunit consisted of two low molecular weight components, one in size similar to prealbumin and one slightly smaller, which appears to be a degradation product of prealbumin. The proportion between the two components seems to vary. It is concluded that besides the presence of an abnormal prealbumin, other factors are of importance for the formation of amyloid precipitates in the vitreous.
Intracellular neurofibrillary tangles is one of the most characteristic findings in Alzheimer's disease and senile dementia of Alzheimer type. In the present paper the authors show that intracellular accumulation of paired helical filaments is also a constant finding in the epithelial cells of the choroid plexus of aging persons. Like the neurofibrillary tangles, the fibrils of the choroid plexus show staining properties typical of amyloid. The nature of the fibrils could not be clarified by electron microscopy or by immunohistochemistry with the use of antisera to gamma-trace or to amyloid fibril proteins of AA and prealbumin type. Amyloid protein AP, found in all amyloid substances except for neurofibrillary tangles and amyloid of senile plaques in the brain, was not demonstrated in the inclusions of the choroid plexus.
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The amino acid sequence of an amyloid-fibril protein Es492 of immunoglobulin-lambda-light-chain origin (AL) was elucidated. The amyloid fibrils were obtained from the spleen of a patient who died from systemic amyloidosis. The amino acid sequence was elucidated from structural studies of peptides derived from digestion of the protein with trypsin, thermolysin, chymotrypsin and Staphylococcus aureus V8 proteinase and from cleavage of the protein with CNBr and BNPS-skatole. A heterogeneity in the length of the polypeptide was seen in the C-terminal region. The protein was by sequence homology to other lambda-chains shown to be of the V lambda II subgroup. Although an extensive homology was seen, some amino acid residues in positions 26, 31, 32, 40, 44, 93, 97, 98 and 99 have not previously been reported in these positions of V lambda II proteins. The significance of these residues in the fibril formation is unclear. The protein was found to contain carbohydrate, with glycosylation sites in two of the hypervariable regions.
Protein AA was purified from the kidneys of dogs with spontaneous reactive amyloidosis. The protein had a blocked N-terminal. Sequence analysis of a peptide obtained after cyanogen bromide cleavage revealed an amino acid sequence corresponding to positions 24-42 of human AA. This region showed a strong homology to protein AA of other species. Antiserum to both human and dog protein AA reacted immunohistochemically with AA amyloid of human, dog and cow origin.
A prealbumin (PA)-like protein was demonstrated in amyloid fibrils both from a patient with senile systemic amyloidosis (SSA) and from a patient in northern Sweden with familial amyloidotic polyneuropathy (FAP). The investigated properties of this protein were similar in the two types of fibrils. The protein had molecular weight, antigenic determinants, and at least one cysteinyl residue in common with the subunit of normal PA. In contrast to normal PA, it contained disulphide-linked subunits and was to some extent bound to the fibril via the cysteinyl residues. The noncovalent forces between its subunits were weaker than in normal PA. It constituted part of the previously described AScl protein of the SSA fibrils. Proteins with lower molecular weight than the PA monomer were major proteins in both SSA and FAP fibrils. These proteins had similar properties in the two kinds of fibril and may be derived from PA. PA in serum from Swedish patients with FAP and SSA was normal with regard to the isoelectric pH of the monomers and tetramers.
Utilizing islet amyloid-laden pancreatic tissues from six diabetic cats, we demonstrated substantial immunoreactivity (peroxidase-antiperoxidase technique) of the islet amyloid with antiserum to a B chain-rich insulin fraction, but no reactivity with antisera to insulin, glucagon, or somatostatin. Islet amyloid was purified from two cats and a protein unique to the diabetic and islet amyloid-laden cats was separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Immunoreactivity of this protein with antiserum to the B chain-rich insulin fraction was also shown by immunoblotting. Attempts to obtain the amino acid composition of the purified unique protein (represented by a single 25,000 dalton band on gel electrophoresis) were not successful because the amount of protein was too small. These results provide important additional evidence that an insulin-related protein is involved in the formation of islet amyloid. Our study also shows that the diabetic cat provides several advantages for the continued study of the etiopathogenic relationship of islet amyloid and diabetes mellitus.