A variant of prealbumin from amyloid fibrils in familial polyneuropathy of Jewish origin

Multidisciplinary Approaches for Transthyretin Amyloidosis

Amyloidosis caused by systemic deposition of transthyretin (TTR) is called ATTR amyloidosis and mainly includes hereditary ATTR (ATTRv) amyloidosis and wild-type ATTR (ATTRwt) amyloidosis. Until recently, ATTRv amyloidosis had been considered a disease in the field of neurology because neuropathic symptoms predominated in patients described in early reports, whereas advances in diagnostic techniques and increased recognition of this disease revealed the presence of patients with cardiomyopathy as a predominant feature. In contrast, ATTRwt amyloidosis has been considered a disease in the field of cardiology. However, recent studies have suggested that some of the patients with ATTRwt amyloidosis present tenosynovial tissue complications, particularly carpal tunnel syndrome, as an initial manifestation of amyloidosis, necessitating an awareness of this disease among neurologists and orthopedists. Although histopathological confirmation of amyloid deposits has traditionally been considered mandatory for the diagnosis of ATTR amyloidosis, the development of noninvasive imaging techniques in the field of cardiology, such as echocardiography, magnetic resonance imaging, and nuclear imaging, enabled nonbiopsy diagnosis of this disease. The mechanisms underlying characteristic cardiac imaging findings have been deciphered by histopathological studies. Novel disease-modifying therapies for ATTR amyloidosis, such as TTR stabilizers, short interfering RNA, and antisense oligonucleotides, were initially approved for ATTRv amyloidosis patients with polyneuropathy. However, the indications for the use of these disease-modifying therapies gradually widened to include ATTRv and ATTRwt amyloidosis patients with cardiomyopathy. Since the coronavirus disease 2019 (COVID-19) pandemic, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, occurred, the minimization of hospital visits and telemedicine have become increasingly important. As older age and cardiovascular disease are major factors associated with increased disease severity and mortality of COVID-19, many ATTR amyloidosis patients are at increased risk of disease aggravation when they are infected with SARS-CoV-2. From this viewpoint, close interspecialty communication to determine the optimal interval of evaluation is needed for the management of patients with ATTR amyloidosis.

Amyloid fibrils containing fragmented ATTR may be the standard fibril composition in ATTR amyloidosis

Abstract The clinical phenotype of familial ATTR amyloidosis depends to some extent on the particular mutation, but differences exist also within mutations. We have previously described that two types of amyloid fibril compositions exist among Swedish ATTRV30M amyloidosis patients, one consisting of a mixture of intact and fragmented ATTR (type A) and one consisting of mainly intact ATTR (type B). The fibril types are correlated to phenotypic differences. Patients with ATTR fragments have a late onset and develop cardiomyopathy, while patients without fragments have an early onset and less myocardial involvement. The present study aimed to determine whether this correlation between fibril type and phenotype is valid for familial ATTR amyloidosis in general. Cardiac or adipose tissues from 63 patients carrying 29 different TTR non-V30M mutations as well as 13 Japanese ATTRV30M patients were examined. Fibril type was determined by western blotting and compared to the patients' age of onset and degree of cardiomyopathy. All ATTR non-V30M patients had a fibril composition with ATTR fragments, except two ATTRY114C patients. No clear conclusions could be drawn about a phenotype to fibril type correlation among ATTR non-V30M patients. In contrast, Japanese ATTRV30M patients showed a similar correlation as previously described for Swedish ATTRV30M patients. This study shows that a fibril composition with fragmented ATTR is very common in ATTR amyloidosis, and suggests that fibrils composed of only full-length ATTR is an exception found only in a subset of patients.

Amyloid deposits in transthyretin-derived amyloidosis: cleaved transthyretin is associated with distinct amyloid morphology

The pathological fibrillar deposits found in the heart and other organs of patients with senile systemic amyloidosis (SSA) and Swedish familial amyloidotic polyneuropathy (FAP) contain wild-type (wt) and a mutant form of transthyretin (TTR), respectively. Previously, it was reported that these two forms of amyloid have different molecular features and it was thus postulated that the mechanism responsible for TTR fibrillogenesis in SSA and FAP may differ. To document further the nature of the amyloid in these entities, detailed morphological, histochemical, immunological, and structural analyses of specimens obtained from 14 individuals with SSA and 11 Swedish FAP patients have been performed. Two distinct patterns of amyloid deposition (designated A and B) were evident. In pattern A, found in all SSA and five of 11 FAP cases, the amyloid had a homogeneous but patchy distribution within the sub-endocardium, sub-epicardium, and myocardium; exhibited weak congophilia and green birefringence; and was composed of tightly packed, short, unorientated fibrils. This material contained mainly approximately 79-residue C-terminal fragments of the amyloidogenic precursor protein. In pattern B, seen in the six other FAP patients, the amyloid appeared as thin streaks throughout the cardiac tissue; often surrounded individual muscle cells; was strongly congophilic and birefringent; had long fibrils arranged in parallel bundles, often penetrating into myocytes; and was composed of virtually intact TTR molecules. These findings provide substantive evidence for the morphological and structural heterogeneity of TTR fibrils and suggest that the two types of deposition may reflect fundamental differences in the pathogenesis of the TTR-associated amyloidoses.

Vitreous amyloidosis in familial amyloidotic polyneuropathy. Report of a case with the Val30Met transthyretin mutation

We present a clinical pathological review of vitreous amyloidosis in a case of familial amyloidotic polyneuropathy, type I. Vitreous opacification was the first manifestation of disease in the proband, who was successfully treated with vitrectomy. The eyes were obtained at autopsy after the patient died from an unrelated cause, and the histopathology is presented here. Analysis of DNA from the pathology specimen revealed the most commonly reported transthyretin mutation, Val30Met. The classification of systemic and ocular amyloidosis as well as the genetics of familial amyloidotic polyneuropathy are briefly reviewed.

Ocular amyloidosis, with special reference to the hereditary forms with vitreous involvement

The complex of diseases referred to as amyloidosis is characterized by the deposition of amyloid substance in various tissues. The amyloid protein differs in the various forms of amyloidosis. This variation is the basis of the differences in affected tissues and subsequent clinical dissimilarities. Vitreous involvement in amyloidosis seems to be especially linked to some of the hereditary neuropathies associated with the amyloid protein transthyretin. Characterization of the amyloid proteins during recent decades has allowed a chemical and immunologic classification of amyloid fibrils. This paper presents the basis for classification of amyloidosis, reviews the literature on ocular amyloidosis, with special reference to vitreous involvement, and summarizes clinical findings and frequency of vitreous amyloid involvement in Swedish patients with familial amyloidotic polyneuropathy.

Amyloid fibrils in Gerstmann-Sträussler-Scheinker disease (Indiana and Swedish kindreds) express only PrP peptides encoded by the mutant allele

Gerstmann-Sträussler-Scheinker (GSS) disease is a cerebral amyloidosis linked to mutations of the PRNP gene. We previously reported that the amyloid protein in the Indiana kindred of GSS is an internal fragment of prion protein (PrP). To investigate whether this fragment originates only from mutant or from both mutant and wild-type PrP, we have characterized amyloid proteins purified from patients of the Indiana and Swedish GSS families. These patients were heterozygous for the Met-Val polymorphism at PRNP codon 129 and carried a mutation at PRNP codon 198 (Phe-->Ser) and codon 217 (Gln-->Arg), respectively. The smallest amyloid subunit was a 7 kDa peptide spanning residues approximately 81 to approximately 150 in the Indiana patient and approximately 81 to approximately 146 in the Swedish patient. In both patients, only Val was present at position 129. Since Val-129 was in coupling phase with Ser-198 and Arg-217, our findings indicate that only the mutant PrP is involved in amyloid formation in both kindreds.

Isolation and purification of amyloid protein A by sodium dodecyl sulphate polyacrylamide gel electrophoresis and reversed-phase high-performance liquid chromatography

Sodium dodecyl sulphate polyacrylamide gel electrophoresis and reversed-phase high-performance liquid chromatography (HPLC) were used consecutively for the isolation of amyloid protein A (protein AA) from amyloid fibrils. Highly purified protein AA was obtained and determined by electrophoretic and amino acid analyses. The heterogeneity of protein AA was shown by HPLC. The isoforms of protein AA had different hydrophobicities, although they were equal in size and similar in amino acid composition. Compared with the conventional amyloid separation procedure (gel permeation chromatography), this technique is rapid, requires only small amounts of amyloid fibrils and may provide new information on amyloid proteins.

Gelsolin-related amyloidosis. Identification of the amyloid protein in Finnish hereditary amyloidosis as a fragment of variant gelsolin

The Finnish type of familial amyloidosis is a systemic disease characterized by progressive cranial neuropathy, corneal lattice dystrophy, and distal sensimotor neuropathy. Amyloid fibrils were isolated from the kidney and heart of a patient with Finnish amyloidosis. After solubilization, the amyloid proteins were fractionated by gel filtration and purified by reverse-phase HPLC. Complete amino acid sequence analyses show that the two amyloid components obtained are fragments of gelsolin, an actin-modulating protein occurring in plasma and the cytoskeleton. The larger component represents residues 173-243 and the minor component residues 173-225, respectively, of mature gelsolin. When compared with the predicted primary structure of human gelsolin a single amino acid substitution is present in amyloid: at position 15 of the amyloid proteins an asparagine is found instead of an aspartic acid residue at the corresponding position (187) in gelsolin. Antibodies to a dodecapeptide of the amyloidogenic region of gelsolin specifically stain the tissue amyloid deposits in Finnish hereditary amyloidosis. The results show that the amyloid subunit protein in Finnish hereditary amyloidosis represents a new type of amyloid that is derived from an actin filament-binding region of a variant gelsolin molecule by limited proteolysis.

Amyloidosis of the nervous system

Various types of amyloid fibril deposits occur in the nervous system with unique clinical characteristics and pathogeneses. Genetic mutations cause the familial amyloidotic polyneuropathies and acquired polyneuropathies occurring particularly in patients suffering from hypernephromas and myelomas also result from the production of abnormal proteins. Amyloid fibril deposits in cerebral plaques and vessels consisting of beta-protein are seen in acquired and familial Alzheimer's disease and in Down's syndrome individuals over 40 years of age. This amyloid fibril deposition could result from a mutational, transcriptional or post-translational alteration in these pathologic processes with most evidence supporting the latter. Other diseases including hereditary cerebral hemorrhage of the Dutch type and Batten's disease involve beta-amyloid deposition. The features of the familial and transmissible forms of the spongiform encephalopathies are associated with the prion protein which comprises the amyloid fibril deposits in these conditions. This wide variety of nervous system disorders having amyloid deposits as their primary or subsidiary characteristic make studies of these conditions intriguing models for research workers in clinical, pathologic and molecular biologic fields.

Type I familial amyloid polyneuropathy in a Chinese family

A Chinese family with at least 3 members having the typical clinical picture of type I familial amyloid polyneuropathy is presented. The pathological features, including the immunohistochemical typing of the amyloid deposits, are described and the literature is briefly reviewed.

Systemic senile amyloidosis. Identification of a new prealbumin (transthyretin) variant in cardiac tissue: immunologic and biochemical similarity to one form of familial amyloidotic polyneuropathy

Isolated amyloid fibrils from three cases of systemic senile amyloidosis (SSA) contained subunit proteins with molecular masses of 14 (10-20%), 10-12 (60-80%), and 5-6 kD (5-10%) when fractionated under reducing and dissociating conditions. This grouping was identical to that seen in SKO, a case of familial amyloidotic polyneuropathy (FAP) studied earlier. Amino acid sequencing confirmed that SSA subunit proteins were in fact prealbumin (transthyretin). Complete sequence analysis of one SSA preparation revealed the presence of a new variant Pa (TTr) molecule with a single amino acid substitution of isoleucine for valine at position 122. Further studies used an antiserum specific for SKO IV, a subunit protein of SKO previously shown to correspond to carboxy-terminal 78 residues (positions 49-127) of (TTr). Anti-SKO IV reacted with SSA in tissue at equivalent dilutions to anti-Pa (TTr) and with the 10-12-kD fraction of SSA on Western blots; reactivity was blocked by SKO IV, but not by Pa (TTr). SSA is a form of systemic amyloidosis caused by tissue deposition of Pa (TTr) and its fragments, with shared conformational or subunit antigenicity to at least one form of FAP. Identification of a new variant Pa (TTr) molecule in one case suggests further that SSA may be a genetically determined disease expressed late in life.

Reduced prealbumin (transthyretin) in CSF of severely demented patients with Alzheimer's disease

Prealbumin (transthyretin) quantified in CSF was negatively correlated with degree of dementia in 24 patients with dementia of Alzheimer type (DAT). There was neither a significant correlation between prealbumin in serum and degree of dementia nor between prealbumin in CSF and number of T lymphocytes in serum. There was no such relationship in 7 patients with multi-infarct dementia. Prealbumin was also quantified in 4 non-demented control groups, one consisting of 14 age- and sex-matched neurological patients, 17 with MS, 6 with ALS and 10 patients who had had a subarachnoid hemorrhage. Prealbumin was significantly lower in the last group. The study suggests that there may be a relationship between prealbumin levels in cerebrospinal fluid and degree of dementia. It is suggested that this may be caused by affection of the choroid plexus.

Familial amyloidotic polyneuropathy: transthyretin (prealbumin) variants in kindreds of Italian origin

As part of an epidemiological study that aims to characterize chemically the mutation(s) in transthyretin (TTR) related to familial amyloidotic polyneuropathy (FAP) of different ethnic origins, studies were carried out on TTR from two FAP kindreds of Italian origin. Two different criteria were employed in the characterization of TTR from these kindreds: (1) immunoblotting of cyanogen bromide fragments for screening of TTR(Met30) and (2) isoelectric focusing. TTR(Met30) was not detected but other substitutions were demonstrated using isoelectric focusing techniques. One of the variants found is a basic TTR variant. The substitutions occurring in the variant TTRs of these two kindreds are not known and are presently under study.

The clinical and biochemical spectrum of hereditary amyloidosis

Familial amyloidosis, once described as a puzzling and highly unusual form of polyneuropathy, is now recognized to be a collection of familial diseases with usually autosomal-dominant inheritance and widespread ethnic distribution. Familial amyloidosis occurs throughout the world and encompasses an extremely broad spectrum of clinical manifestations. In some families, progressive peripheral neuropathy dominates the illness, while in others, renal failure, ocular amyloid deposits, cardiac decompensation, or intracranial hemorrhage is the most significant clinical feature. The Portuguese (type I) and the Iowa (type III) neuropathies characteristically begin with lower limb involvement, while in the Indiana (type II) form, upper limb neuropathy is seen first; in the Japanese families with familial amyloid polyneuropathy, symptoms first become evident around age 40, whereas in the Texas family, onset is in the seventh decade. The prognosis for the different families is highly variable. Current classification of the familial amyloid polyneuropathy syndromes is based on their characteristic clinical presentations, but ongoing biochemical identification of the protein composition of amyloid substance in each form will make a more rational nosology feasible in the near future. To date, no therapy has been shown to arrest or reverse the progressive accumulation of amyloid deposits in most forms of familial amyloidosis. Familial Mediterranean fever is a major exception, and the incidence of amyloidosis associated with this disease has been dramatically reduced by the widespread prophylactic use of colchicine. Technology currently available permits the reliable identification of asymptomatic relatives at risk for developing amyloid neuropathy as well as the prenatal identification of carriers of the mutant transthyretin gene. These strategies can be used in genetic counseling aimed at reducing the continued propagation of the mutant gene.

Transthyretin is synthesized in the mammalian eye

Transthyretin (TTR, prealbumin) is a 55 kDa protein which plays an important role in the plasma transport of thyroxine and retinol. Although the liver and choroid plexus are the two major known sites of TTR synthesis, several lines of evidence suggest the possibility of a separate ocular source of TTR. We report the presence of TTR mRNA in rat and bovine eye and of TTR in rat eye. Preliminary immunohistochemical data indicate that the retinal pigment epithelium is a major site of TTR immunoreactivity in the rat. While the functional significance of ocular TTR synthesis is unclear, TTR may be involved in the ocular translocation and processing of retinol. The finding of TTR synthesis in the eye may explain ocular involvement in the familial amyloidotic polyneuropathies.

Metabolism of senile amyloid precursor and amyloidogenesis. Age-related acceleration of apolipoprotein A-II clearance in the senescence accelerated mouse

Serum clearance kinetics of murine senile amyloid-related high-density lipoprotein (HDL) apoprotein A-II (apo A-II) was examined in the senescence-accelerated mouse, prone (SAM-P/1) and resistant (SAM-R/1), with 125I-HDL purified from both strains. In SAM-R/1, with 125I-HDL purified from both strains. In SAM-R/1, the serum half-life of apo A-II was not altered with increasing age and was practically identical to that of apo A-I. In 2-month old SAM-P/1, the serum half-life of both apo A-I and apo A-II was generally the same as observed in SAM-R/1. However, at age 6 and 12 months, in SAM-P/1, the serum half-life of apo A-II decreased significantly and was less than that of apo A-I. These age-related changes in apo A-II clearance kinetics were observed regardless of the HDL donor. The authors also examined the tissue distribution of injected apo A-II, using 125I-apo A-II reconstituted HDL, and found that several organs trapped more 125I radioactivity in old SAM-P/1 than in young mice. This evidence strongly suggests that age-related changes in the metabolic environment of apo A-II might affect senile amyloidogenesis in SAM-P/1.

A new prealbumin variant in familial amyloid cardiomyopathy of Danish origin

A C-terminal fragment of a prealbumin variant was isolated from amyloid material obtained from the myocardium of a patient (Han) with familial amyloid cardiomyopathy of Danish origin. The prealbumin variant fragment was shown to have a methionine for leucine substitution in position 111.

Degradation and deposition of amyloid AA fibrils are tissue specific

The complete amino acid sequences of two related AA proteins (Mr 9700 and 5300) derived from thyroid tissue from a patient, NOR, with the autosomal recessive disease familial Mediterranean fever were determined. Heterogeneity found at position 52 indicates these proteins are fragments of two allelic or isotypic SAA precursor molecules similarly degraded at unusual sites and deposited in the thyroid. Degradation appears to be tissue and/or enzyme(s) specific since the carboxy terminus of both fragments is Ala-Ala and is different from other AA amyloid fibrils extracted from various tissues in different patients. Electron micrographic studies reveal these fragments retain the characteristics of native amyloid fibrils under physiological conditions even after exposure to dissociating agents.

Hereditary cystatin C (gamma-trace) amyloid angiopathy of the CNS causing cerebral hemorrhage

Hereditary CNS amyloid angiopathy occurring in Icelanders is the first human disorder known to be caused by deposition of cystatin C amyloid fibrils in the walls of the brain arteries leading to single or or multiple strokes with fatal outcome. One or more affected members have been verified by histological examination in 8 families containing 127 affected. These originated from the same geographic area. Abnormally low value of cystatin C found in the cerebrospinal fluid of those affected can be used to support or make diagnosis of this disease, also in asymptomatic relatives. By amino acid sequence analysis the amyloid fibrils in the patients are found to be a variant of cystatin C (gamma-trace), a major cysteine proteinase inhibitor. The variant protein has an amino acid substitution (glutamine for leucine) at position 58 in the amyloid molecule. It is postulated that a point mutation has occurred leading to production of amyloidogenic protein causing the disorder.

Onset in the seventh decade and lack of symptoms in heterozygotes for the TTRMet30 mutation in hereditary amyloid neuropathy-type I (Portuguese, Andrade)

In a Portuguese-American family with hereditary amyloid neuropathy (familial amyloidotic polyneuropathy), onset was in the seventh decade in all affected relatives. Another unusual characteristic was their origin from the Portuguese island of Madeira. In spite of this, the mutant transthyretin (TTRMet30) (the same variant prealbumin that is the circulating precursor of AFP protein in the classic Portuguese patients) could be found in the propositus' plasma. In addition, three other asymptomatic relatives (ages 90, 73, and 48) were shown to carry the mutation. Late onset and incomplete penetrance, at a clinical level, raise problems for presymptomatic detection of mutant TTR, as these tend to cluster in families. When counseling asymptomatic heterozygotes, we must consider intra-familial correlation in age-of-onset, and the distribution of age-of-onset including age of unaffected heterozygotes. This family poses interesting questions regarding pathogenesis of this degenerative process and the influence of other genetic factors, such as modifiers, epistasis, and polymorphism of the TTR genes or their regulators. A cis-effect of a gene linked to the mutant gene, decreasing the synthesis of the mutant TTR and keeping a sufficient amount of the normal one in circulation, or producing some cofactor for TTR, could also explain late onset and apparently incomplete penetrance; the occasional finding of classic forms in these families would be the result of recombinatory events.

Pars plana vitrectomy for vitreous amyloidosis

Thirty-six pars plana vitrectomies were performed on 30 eyes of 17 patients with biopsy-proven vitreous amyloidosis. Reopacification of the retrolental vitreous was the most common reason for vitrectomy revision, required in 24% of patients. Complications of amyloid or vitrectomy included retinal detachment requiring scleral buckling in 17% of eyes and glaucoma requiring filtering surgery in 17% of eyes. After a mean 35-month post-vitrectomy follow-up, 48% of eyes had visual acuities of 20/40 or better, and 32% of eyes had visual acuities between 20/50 and 20/100. Twenty percent of eyes had visual acuities of 20/200 or worse due either to persistent retinal detachment, open angle glaucoma, or residual opacification of the vitreous.

Preparative fractionation of amyloid proteins on a microgram scale by high-performance liquid chromatography and polyacrylamide gel electrophoresis

Preparative separation of amyloid proteins on a microgram scale is presented. Amyloid fibrils solubilized in aqueous 50% acetonitrile containing 0.1% trifluoroacetic acid, are fractionated by reverse-phase high-performance liquid chromatography. Fractionation of amyloids obtained from patients with familial Mediterranean fever allowed isolation of a protein identical with a conventionally isolated AA-protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis is used for preparative separation of AL-proteins. Two protein extraction procedures from Coomassie Blue stained gels are applied using elution in 0.1% sodium dodecyl sulfate containing buffer and 6 mol/l guanidine-HCl solution. The eluted proteins are concentrated and sodium dodecyl sulfate and dye are removed by acetonitrile precipitation of sample.

Hereditary amyloidosis: description of a new American kindred with late onset cardiomyopathy. Appalachian amyloid

A family with hereditary amyloidosis characterized by peripheral neuropathy and cardiomyopathy is described. Lack of eye involvement sets their disease apart from the Indiana/Swiss familial amyloidotic polyneuropathy type II. The disease is of late onset; affected members die of cardiomyopathy after age 60. The late onset and lack of clinically significant neuropathy in several family members has led to misdiagnosis of the cardiomyopathy. Immunohistochemistry using antiprealbumin antiserum showed staining of amyloid deposits in nerve and heart.

Prealbumin: its association with amyloid

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.

Immuno-enhancing activity of the amino-terminal domain of human prealbumin: isolation, characterization and synthesis

A decapeptide isolated from highly purified preparations of human prealbumin was able to restore azathioprine (Az) sensitivity, a property of a sub-class of T-lymphocytes, to the spleen rosette-forming cells (RFC) of adult thymectomized (ATx) mice in vitro. The peptide was sequenced by the Edman method and shown to correspond to the ten amino-terminal residues of prealbumin, Gly-Pro-Thr-Gly-Thr-Gly-Glu-Ser-Lys-Cys. Synthesis of this peptide by solid phase methodology confirmed its activity both in vitro and in vivo. Synthesis of a number of structural analogues indicated that the amino-terminal deca, undeca and dodecapeptides of prealbumin as well as some of their derivatives were also able to restore Az sensitivity to RFC in vitro and in vivo. The Cys10 residue and the Glu7 residues both contributed significantly to potency in vitro. Removal of up to three amino acids from the N-terminus of the decapeptide led to a progressive loss of activity. The data indicates that the ability of human prealbumin to restore the Az sensitivity to the RFC of adult Tx mice is intrinsic to the protein and resides in the amino-terminal domain of the molecule.

Characterization of a transthyretin (prealbumin) variant associated with familial amyloidotic polyneuropathy type II (Indiana/Swiss)

Amyloid fibrils were isolated from cardiac tissue of two brothers who died from familial amyloidotic polyneuropathy (FAP) type II. Sequence analysis on peptides derived from proteolytic cleavage with trypsin and fragmentation with cyanogen bromide reveal that the fibril subunit protein is derived from plasma transthyretin (prealbumin). About two-thirds of the fibril subunit protein was found to contain an amino acid substitution at position 84 where the normal isoleucine residue has been replaced by serine. Sequence analysis of the plasma transthyretin (prealbumin) from the two brothers as well as two clinically diagnosed FAP type II family members and two of four children of affected individuals showed the presence of serine at position 84. The presence of this substitution also correlates with low serum levels of retinol-binding protein and thus transthyretin (prealbumin) position 84 may be involved with the interaction of these two proteins.

Biochemical and molecular genetic characterization of a new variant prealbumin associated with hereditary amyloidosis

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant late-onset disorder characterized by the extracellular deposition of amyloid fibrils. In all cases studied these fibrils have been found to be composed of plasma prealbumin (transthyretin) containing a single amino acid substitution. Biochemical studies were conducted on amyloid from one patient and plasma prealbumin from his affected brother, both part of a large kindred from the Appalachian region of the United States. Sequence analysis of the amyloid subunit protein showed it to be prealbumin with about two-thirds of the molecules containing a substitution of alanine for threonine at position 60. Studies of the plasma prealbumin showed that the same substitution was present in 40-45% of the protein. Based on this substitution and the prealbumin cDNA sequence, a Pvu II restriction fragment length DNA polymorphism (RFLP) was predicted and demonstrated in DNA of both patients as well as other family members. This RFLP confirms the predicted DNA mutation responsible for the protein variant, and represents an accurate method for detection of this gene.

Characterization of amyloid protein AA and its serum precursor SAA in the horse

Amyloid was extracted from the liver of a horse that had developed amyloidosis after being used for several years for the production of antibodies to bacterial antigens. The amyloid fibrils were shown to be of the AA type. Two AA proteins with molecular weights of 9000 and 11,000 and with identical partial N-terminal amino acid sequences were identified. Marked structural homology with AA from other species including man was seen, although clear species-related antigenic specificity was observed. SAA isolated from an acute phase (septic abortion) horse serum was identical to AA with respect to antigenicity and the 10 first N-terminal amino acid residues that have been studied up to now. The bulk of SAA was present in the high-density lipoprotein complex in serum. Also SAA was heterogeneous with respect to size, most molecules having a molecular weight of 11,000, and a minority 9000.

Polymorphism in a kappa I primary (AL) amyloid protein (BAN)

In an attempt to understand the relationship of amino acid sequence to the formation of primary or multiple myeloma-related amyloid (AL amyloid), we have determined the complete amino acid sequence of amyloid protein BAN. This protein belongs to the kappa I immunoglobulin light chain subgroup and has a polypeptide chain length of 126 amino acids. It encompasses the entire variable region, the joining segment and the first tryptic peptide of the constant region. This protein has two unique features. First, the molecule is glycosylated. At position 61 the usual arginine residue has been replaced by an asparagine with the generation of the signal sequence Asn-Phe-Thr, to which a glucosamine-containing carbohydrate unit is attached. Secondly, the protein is not monoclonal but consists of two chains which have the same variable region but different J-segments. Comparison of the BAN sequence with other amyloid and nonamyloid kappa I proteins reveals a systematic difference between the two groups. In the amyloid proteins, several hydrophilic framework residues have been replaced by hydrophobic residues. These substitutions may provide the nucleation sites for self-aggregation and fibril formation.

Characterization of amyloid deposits in biopsies of 15 with "sporadic" (non-familial or plasma cell dyscrasia amyloid polyneuropathy

Review of the clinical and laboratory findings of 39 patients with amyloid polyneuropathy (AP) showed 12 cases to be hereditary and 12 to be associated with plasma cell dyscrasia (PCD). The remaining 15, termed "sporadic" AP, had neuropathy clinically indistinguishable from the other two groups but without a clinicopathologically identified PCD or positive family history. In an attempt to identify the type of amyloid in "sporadic" AP, the immunoreactivity of amyloid deposits was investigated using specific antisera raised against the following different chemical types of amyloid fibril proteins: variable regions of amyloid light chains kappa (A kappa) and lambda (A lambda), amyloid protein AA, and prealbumin. It was found that the amyloid in "sporadic" AP had A lambda antigenic determinants in ten cases, A kappa in one and prealbumin in three; in one case, the A lambda nature of amyloid was confirmed biochemically on the extracted amyloid fibrills. Thus, the most common type of AP in our population appears to be the "sporadic" form. In "sporadic" AP, the amyloid is most commonly of immunoglobulin light chain origin, even in the absence of overt PCD, and it can be rapidly categorized immunocytochemically to determine therapeutic directions or provide genetic guidance.

Amino acid sequence of a lambda VI primary (AL) amyloid protein (WLT)

It has been observed that monoclonal immunoglobulin proteins of the lambda VI subgroup have a high propensity to form amyloid deposits. To ascertain whether lambda VI proteins have unique structure determinants that would account for self association and resultant fibril formation, we have determined the complete amino acid sequence of the AL amyloid protein WLT. This protein, isolated from the spleen of a patient with AL amyloid, has 134 amino acid residues and contains the entire variable region, the joining segment, and the first tryptic peptide of the constant region. Comparison of the structure of this protein with the 3 completely sequenced lambda VI proteins reveals that they are highly homologous and contain a 2-residue insertion at positions 68 and 69. Phylogenetic comparisons of the variable domain of all lambda VI proteins reveal that the 3 amyloid proteins WLT, SUT, and AR are all more closely related to each other than to the myeloma protein NIG48. Separating the variable domains into framework (FR) and complementarity-determining regions (CD) and recalculating the phylogenetic comparisons, we identify major substitutions in the FR regions of NIG48 in relation to the amyloid proteins. This supports the hypothesis that the formation of AL amyloid is a result of the secondary structure of the FR regions of the precursor molecules.

Familial amyloid polyneuropathy

Amyloid fibrils were isolated from the myocardium of two patients with familial amyloid polyneuropathy. The solubilized amyloid fibril whole protein shared immunologic determinants with normal human serum prealbumin (transthyretin), but revealed subtle differences on immunoelectrophoresis and radial immunodiffusion. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, amyloid fibril whole protein was resolved into numerous bands that reacted with antitransthyretin on immunoblots. The whole protein also contained peptide fragments of fibronectin, but was devoid of amyloid P protein. An antiserum raised against the whole protein was suitable for immunocytochemistry of amyloid in paraffin sections. In contrast, commercial antitransthyretin, raised against the intact tetrameric protein failed to react with tissue amyloid. Immunochemical and immunocytochemical results support the concept that familial amyloid polyneuropathy with cardiomyopathy is due to infiltration of susceptible tissues by an anomalous transthyretin.

Amyloid fibrils derived from V-region together with C-region fragments from a lambda II-immunoglobulin light chain (HAR)

Amyloid fibril proteins were isolated from the spleen of a patient with IgD(lambda)-plasmocytoma by extraction and gel filtration in 5M guanidine hydrochloride. The molecular mass of the predominant polypeptide chain was approximately 5000 Da. Its complete amino-acid sequence was elucidated by stepwise automated degradation of the carboxymethylated polypeptide chain and by structural studies of tryptic and thermolysinolytic cleavage products. The length of the polypeptide chain was 58 to 59 residues and it was homologous to the amino acids in positions 8 through 65 of the variable part of an lambda-type immunoglobulin light chain, which was most closely related to the lambda II subgroup. The N-terminal sequence of this amyloid fibril protein proved to be heterogeneous, indicating cleavage after the amino acids in positions 7 and 8. Peptides from the constant part of the lambda-chain were unexpectedly found in the tryptic digest of the denatured amyloid protein HAR. One polypeptide derived from the constant region was separated from the main component by high performance liquid chromatography. Its amino-acid sequence commenced at position 111 and could be traced in 41 steps. In this case, at least two constant region fragments were shown to be constituents of the amyloid fibril protein. The association of fragments from the variable as well as the constant region is discussed with respect to amyloid formation.

The amyloid in familial amyloid cardiomyopathy of Danish origin is related to pre-albumin

Amyloid obtained from the myocardium of a patient (Han) with familial amyloid cardiomyopathy of Danish origin was studied. Gel filtration and electrophoresis of purified and denatured amyloid fibrils Han revealed various fractions ranging in mol. wt from 40,000 to 8,000 daltons. Amyloid Han and fractions reacted with an antiserum against amyloid Han showing a reaction of identity with each other; partial identity between Han and human pre-albumin was observed, while no reaction was seen with AA or AL proteins. Cardiac tissue sections from Han showed reactivity with antisera to amyloid Han, pre-albumin and protein AP, but not with anti-AA or anti-AL in indirect immunofluorescence. Amino acid composition and sequence studies of a protein fraction of amyloid Han with mol. wt 15,000 daltons confirmed the structural relationship with pre-albumin.

Lowered prealbumin levels in patients with familial amyloid polyneuropathy (FAP) and their non-affected but at risk relatives

Amyloid fibrils in familial amyloid polyneuropathy, the familial (AF) form of systemic amyloidosis, are composed of the monomeric unit (14,000 MW) of prealbumin molecules. By radioimmunoassay, the serum level of prealbumin was measured in 25 patients from 12 different kinships with this dominantly inherited form of amyloidosis and 56 unaffected, but at risk, relatives from two of the kinships. Results were compared to prealbumin levels in normal individuals and patients with primary (AL) and secondary (AA) forms of systemic amyloidosis. Significantly lowered prealbumin levels were found in the AF patients (149.2 micrograms/ml) and their at risk relatives (169.0 micrograms/ml) when compared to normal individuals (232.9 micrograms/ml), AL patients (221.9 micrograms/ml) and AA patients (211.7 micrograms/ml). No abnormality was found in levels of retinol binding protein (RBP), which is carried by prealbumin, in the serum of either the AF patients or their relatives. The depressed prealbumin levels may indicate a structural variant molecular form, an extra hepatic synthesis or an abnormality in catabolism of this protein that is present prior to the clinical or histopathologic onset of the AF disease.

Identification of carriers of a variant plasma prealbumin (transthyretin) associated with familial amyloidotic polyneuropathy type I

A method is described for detecting carriers of a variant plasma prealbumin that is associated with familial amyloidotic polyneuropathy (FAP) type I. It is based on the finding of an extra methionine in the variant prealbumin, at position 30 from the amino terminals. Since normal prealbumin has only one methionine (position 13), treatment with cyanogen bromide (CNBr), which cleaves only at methionines, results in two peptides. CNBr treatment of the variant prealbumin gives three peptides. The extra can then be detected in two ways: by HPLC using a reverse phase C18 column, and by sequential Edman degradation. Each method can detect as little as 1% variant prealbumin in isolated plasma prealbumin, and therefore, can identify carriers of the gene for the variant protein. Since FAP type I usually is not manifest until after the childbearing years, this method to identify carriers of the gene offers a new approach for genetic counseling of families with this disease. To date, kindreds with hereditary amyloidosis that could benefit from these studies include those with FAP type I of Swedish, Japanese, and Portuguese origins.

Family studies of the genetic abnormality in transthyretin (prealbumin) in Portuguese patients with familial amyloidotic polyneuropathy

Amyloid deposits in several heredofamilial forms of amyloidosis are chemically related to transthyretin (TTR, the protein usually referred to as prealbumin). A genetically abnormal TTR may be involved. Studies were conducted on TTR isolated from sera of patients with familial amyloidotic polyneuropathy (FAP), and on amyloid fibril protein (AFp) isolated from tissues of two Portuguese patients who died with FAP. AFp, purified by affinity chromatography on retinol-binding protein (RBP), resembled plasma TTR in forming a stable tetrameric structure, and in its binding affinities for both thyroxine and RBP. Purified AFp was found to comprise a TTR variant with a methionine for valine substitution at position 30. This conclusion was based upon studies that included: (i) comparative peptide mapping by reverse-phase high-performance liquid chromatography after trypsin digestion; (ii) cyanogen bromide (CNBr) cleavage studies; and (iii) amino acid microsequence analysis of selected tryptic and CNBr peptides. The variant TTR was also found to be present in serum samples from FAP patients, along with larger amounts of normal TTR. An effective, small-scale procedure was developed to determine whether or not the variant TTR was present in the plasma of an individual subject. This procedure involved isolation of TTR by affinity chromatography on RBP, followed by CNBr cleavage, and analysis for the presence of specific aberrant CNBr peptides. Studies with six kindreds, including 21 asymptomatic children of 6 patients with FAP, showed that the "abnormal" TTR can be detected and used as a preclinical marker of the disease in affected children of patients with FAP. It is likely that the variant TTR represents a point mutation within the TTR structural gene, and that the normal and mutant genes act as co-dominant alleles at a single locus in FAP. The distribution of the mutant TTR within the six families was consistent with the autosomal dominant mode of inheritance of FAP. The mutant TTR apparently selectively deposits in tissues as the amyloid characteristic of the disease.

Lack of evidence for protein AA reactivity in amyloid deposits of lattice corneal dystrophy and amyloid corneal degeneration

Amyloid fibrils occurring in primary and myeloma-associated (AL), secondary (AA), and certain neuropathic hereditary forms of systemic amyloidosis can be distinguished biochemically or immunohistologically as being composed of immunoglobulin light chain, protein AA, or prealbumin respectively. All types of systemic and several localized forms of amyloidosis contain amyloid P component (protein AP). We studied formalin-fixed tissue from eight cases of lattice corneal dystrophy by the immunoperoxidase method using antisera to proteins AA and AP, to normal serum prealbumin and prealbumin isolated from a case of hereditary amyloidosis, and to light-chain determinants; additional cases were examined by indirect immunofluorescence of fresh-frozen material. We found weak (1:10 dilution) staining with anti-AP, but no reactivity with other antisera. Congo red staining was resistant to pretreatment of sections with potassium permanganate, a characteristic of non-AA amyloid. Two-dimensional gels of solubilized proteins from frozen tissue from two cases of lattice corneal dystrophy resembled those obtained from normal human cornea. Western blots of two cases of polymorphous amyloid degeneration and solubilized protein from normal cornea did not react with radioactive iodine-labeled anti-AA or anti-AP with purified protein AP and unfixed protein AA amyloid tissue as controls. We were unable to corroborate the presence of protein AA in the amyloid deposits of lattice corneal dystrophy. Although staining with antiserum to protein AP was demonstrable, the molecular configuration of this protein in stromal deposits remains to be defined.

Amyloid fibril protein in familial amyloidotic polyneuropathy, Portuguese type. Definition of molecular abnormality in transthyretin (prealbumin)

Amyloid fibril protein in patients with familial amyloidotic polyneuropathy is known to be chemically related to transthyretin (TTR), the plasma protein that is usually referred to as prealbumin. A genetically abnormal TTR may be involved in this disease. Studies were conducted on amyloid fibril protein (AFp) isolated from tissues of two Portuguese patients who died with familial amyloidosis, and on TTR isolated from sera of patients with this disease. AFp, purified by affinity chromatography on retinol-binding protein linked to Sepharose, resembled plasma TTR in forming a stable tetrameric structure, and in its binding affinities for both thyroxine and retinol-binding protein. The structural studies included: (a) comparative peptide mappings by reverse-phase high performance liquid chromatography (HPLC) after trypsin digestion; (b) cyanogen bromide cleavage studies; and (c) amino acid microsequence analysis of selected tryptic and CNBr peptides. On the basis of the known amino acid sequence of TTR, comparative tryptic peptide maps showed the presence of a single aberrant tryptic peptide (peptide 4, residues 22-34) in AFp as compared with TTR. This aberrant peptide contained a methionine residue, not present in normal tryptic peptide 4. CNBr cleavage of AFp produced two extra peptide fragments, which were demonstrated, respectively, by HPLC analysis and by sodium dodecyl sulfate-gel electrophoresis. Sequence analyses indicated the presence of a methionine-for-valine substitution at position 30 in AFp as compared with TTR. Thus, the purified amyloid fibril protein comprised a TTR variant with a methionine-forvaline substitution at position 30. A single nucleotide change in a possible codon for valine 30 could explain the substitution. The variant TTR was also present in the TTR isolated from the pooled sera of amyloidoses patients, together with larger (four- to six-fold) amounts of the normal TTR. Thus, in these patients, the variant TTR was circulating in plasma, along with larger amounts of normal TTR. We suggest that the variant TTR represents the specific biochemical cause of the disease, and that this abnormal form of TTR selectively deposits in tissues as the amyloid characteristic of the disease.

Immunocytochemical demonstration of prealbumin in the vitreous in heredofamilial amyloidosis

Vitreous material obtained at pars plana vitrectomy from a patient with heredofamilial amyloidosis with vitreous involvement and control vitreous from a patient without amyloidosis were subjected to immunocytochemical studies. P component (AP), a minor constituent of all amyloid deposits, was found in trace amounts in the familial amyloid vitreous, but other amyloid proteins, which occur in secondary amyloidosis or in primary amyloidosis, were not found. The major amyloid protein in the vitreous in heredofamilial amyloidosis (but not control vitreous) was found to be prealbumin.

Primary structure of an amyloid prealbumin and its plasma precursor in a heredofamilial polyneuropathy of Swedish origin

Prealbumin from an individual with heredofamilial amyloid polyneuropathy of Swedish origin was isolated from plasma by using a three-step procedure involving ion exchange, Affi-gel Blue affinity chromatography, and gel filtration. This prealbumin and its associated amyloid fibril subunit protein were digested with trypsin and the resulting peptides were separated by high performance liquid chromatography. Comparison with normal prealbumin peptides showed that an amino acid substitution of a methionine for a valine had occurred at position 30. In the plasma prealbumin, the abnormal residue accounted for 1/3rd of the material while in the amyloid fibrils it accounted for 2/3rds. From this sequence information and the known three-dimensional structure of the prealbumin molecule, a mechanism for the amyloid formation is proposed. It involves formation of the amyloid fibrils by addition of prealbumin dimers or tetramers to the aggregate. Each dimer must contain at least one variant peptide chain while the tetramer must contain at least two abnormal chains. Either of these models can account for the observed amount of normal prealbumin in amyloid fibrils. No proteolytic processing of this molecule is required because the entire undegraded prealbumin molecule is found in the fibrils.

Familial amyloid polyneuropathy. Demonstration of prealbumin in a kinship of German/English ancestry with onset in the seventh decade

A family with autosomal dominant transmitted familial amyloid polyneuropathy residing in Texas is described. Clinically, the prominent sensory and severe autonomic nervous system involvement resembles the Andrade (Portuguese) type I familial amyloid polyneuropathy but is unique in that the age of onset is in the seventh decade in all family members affected to date. Using an immunoperoxidase technique, prealbumin was demonstrated in the amyloid deposits. This finding suggests that this family shares biochemical as well as clinical characteristics consistent with similar kinships with type I familial amyloid polyneuropathy of diverse geographic origin.

Prealbumin and retinol binding protein serum concentrations in the Indiana type hereditary amyloidosis

Serum prealbumin and retinol binding protein (RBP) concentrations were determined for 68 members of a kindred in Indiana with a familial type of systemic amyloidosis. Immunohistochemical studies on rectal and muscle biopsy material from individuals with this type of amyloidosis revealed staining of amyloid deposits with anti-prealbumin. Both the serum prealbumin and RBP concentrations were significantly depressed in 9 patients with amyloidosis when compared with normal controls and unaffected kin. In addition, the mean RBP serum concentration of 21 offspring of the patients with amyloidosis was significantly depressed. A more significant finding was that on the basis of the serum RBP concentrations, the offspring could be divided into 2 distinct groups. One group represented approximately 50% of the children and had serum prealbumin and RBP concentrations not significantly different from their afflicted parents. The second group had serum prealbumin and RBP concentrations not significantly different from those of normal controls and non-affected kin. These findings show that prealbumin and RBP serum concentrations are depressed in patients with the Indiana type of hereditary amyloidosis and that these serum abnormalities may be present long before development of clinical disease. They suggest that individuals with this genetic abnormality may be identified prior to clinical expression of the disease.

Amyloid fibril in hereditary cerebral hemorrhage with amyloidosis (HCHWA) is related to the gastroentero-pancreatic neuroendocrine protein, gamma trace

Amyloid fibrils were isolated from the leptomeningeal blood vessels obtained at autopsy from three Icelandic patients dying of Hereditary Cerebral Hemorrhage with Amyloidosis (HCHWA) and verified by Congo red staining and electron microscopy. Gel filtration on Sephadex and Ultrogel columns yielded predominantly one component (molecular weight 11,500 daltons) and also another minor component (molecular weight 15,800 daltons). Automated amino terminal sequencing showed these proteins to be similar (36 residues) to a recently described human protein, gamma trace, beginning at its eleventh amino terminal residue. The amyloid deposits in all three patients stained with rabbit anti-gamma trace antiserum. Although the function of gamma trace is not known, it appears to have structural homology with several hormones and has been localized to the brain, pancreas and pituitary. The amyloid fibril subunits seem to have polymerized after cleavage of the amino terminal decapeptide from gamma trace-related proteins. Therefore, HCHWA appears to be the first genetically determined disease related to the gastroenteropancreatic neuroendocrine system.