Amyloidoma of a spinal root.

A unique case of amyloidoma presenting as a dumbbell-shaped tumor of a spinal root without bony erosion is described. Amyloid was also present in the facial nerve. DNA analysis for transthyretin was negative. Isolated amyloid fibers contained lambda light chains, and although plasma and urine immunoelectrophoresis performed by immunofixation was normal, it is possible the tumor may have been derived from an isolated plasmacytoma.

Renal amyloidosis caused by a novel stop-codon mutation in the apolipoprotein A-II gene.

BACKGROUND: Although apolipoprotein A-II (apoA-II) associated amyloidosis has been described in the senescent accelerated mouse (SAM) model of aging, so far there has been no report of human apoA-II amyloidosis except for a recent report of renal amyloidosis resulting from a stop-codon to glycine mutation of apoA-II. The mechanisms of amyloid formation in human apoA-II amyloidosis are not clear. METHODS: A 46-year-old Caucasian male with proteinuria noted at 42 years of age was studied. Renal biopsy revealed amyloid deposition in glomeruli. DNA analysis of genes known to be associated with hereditary renal amyloidosis revealed no abnormalities. To elucidate the type of his amyloidosis, apoA-II gene and plasma apoA-II were examined. RESULTS: DNA analysis revealed heterozygosity for a G to C transversion at the second position of the stop-codon of apoA-II gene, suggesting a stop to serine substitution at codon 78. Western blot analysis and amino acid sequence analysis of the patient's plasma apoA-II showed both normal apoA-II and variant apoA-II with a 21-amino acid residue extension at the C-terminus. CONCLUSIONS: These results indicate that the patient's amyloid fibrils were derived from apoA-II and the amyloidogenesis is likely to be closely linked to the peptide extension at the C-terminus of variant apoA-II. The pathogenesis of human apoA-II amyloidosis is different from that of SAM.

Shoulder-pad sign of amyloidosis: structure of an Ig kappa III protein.

While amyloid infiltration of articular structures is rare, the 'shoulder-pad' sign resulting from periarticular soft tissue amyloid deposition is essentially pathognomonic for immunogloblin (Ig) (AL) amyloidosis. We report the characterization of an amyloid protein (GRA) which produced articular amyloid deposits and the shoulder-pad sign. Amyloid fibrils were isolated from soft tissue shoulder mass of a patient with systemic AL amyloidosis. The fibrils were solubilized in guanidine HCl and proteins separated by Sepharose chromatography. Amino acid sequence of fractionated protein was determined after tryptic digestion. Sequence analysis of the major amyloid protein yielded a kappa III Ig light chain structure. The entire variable region (VL) plus the constant region (CL) to residue 207 was identified; but lesser amounts of CL than VL were present. A number of amino acid residues previously not observed in kappa III VL proteins, plus a two amino acid insert (95A, 95B), were identified. Kappa III VL amyloid proteins are rare and may show an increased predilection for soft tissue deposition. While several unique amino acid residues that were identified in protein GRA may contribute to soft tissue amyloid deposition, no definite pattern is obvious from comparison with other reported kappa III amyloid proteins.

Prion proteins with different conformations accumulate in Gerstmann-Sträussler-Scheinker disease caused by A117V and F198S mutations.

Gerstmann-Sträussler-Scheinker disease (GSS) is characterized by the accumulation of proteinase K (PK)-resistant prion protein fragments (PrP(sc)) of approximately 7 to 15 kd in the brain. Purified GSS amyloid is composed primarily of approximately 7-kd PrP peptides, whose N terminus corresponds to residues W(81) and G(88) to G(90) in patients with the A117V mutation and to residue W(81) in patients with the F198S mutation. The aim of this study was to characterize PrP in brain extracts, microsomal preparations, and purified fractions from A117V patients and to determine the N terminus of PrP(sc) species in both GSS A117V and F198S. In all GSS A117V patients, the approximately 7-kd PrP(sc) fragment isolated from nondigested and PK-digested samples had the major N terminus at residue G(88) and G(90), respectively. Conversely, in all patients with GSS F198S, an approximately 8-kd PrP(sc) fragment was isolated having the major N terminus start at residue G(74). It is possible that a further degradation of this fragment generates the amyloid subunit starting at W(81). The finding that patients with GSS A117V and F198S accumulate PrP(sc) fragments of different size and N-terminal sequence, suggests that these mutations generate two distinct PrP conformers.

A new human hereditary amyloidosis: the result of a stop-codon mutation in the apolipoprotein AII gene.

Hereditary systemic amyloidosis may be caused by mutations in a number of plasma proteins including transthyretin, apolipoprotein AI, fibrinogen Aalpha-chain, lysozyme, and gelsolin. Each type of amyloidosis is inherited as an autosomal dominant disease and is associated with a structurally altered protein that aggregates to form amyloid fibrils. Here we report that the amyloid protein in a family with previously uncharacterized hereditary renal amyloidosis is apolipoprotein AII (apoAII) with a 21-residue peptide extension on the carboxyl terminus. Sequence analysis of the apoAII gene of affected individuals showed heterozygosity for a single base substitution in the apoAII stop codon. The mutation results in extension of translation to the next in-frame stop codon 60 nucleotides downstream and is predicted to give a 21-residue C-terminal extension of the apoAII protein identical to that found in the amyloid. This mutation produces a novel BstNI restriction site that can be used to identify individuals with this gene by restriction fragment length polymorphism analysis. This is the first report of apoAII amyloid in humans and the first mutation identified in apoAII protein. Amyloid fibril formation from apoAII suggests that this lipoprotein, which is predicted to have an amphipathic helical structure, must undergo a transition to a beta-pleated sheet by a mechanism shared by other lipoproteins that form amyloid.

Binding, trafficking and accumulation of serum amyloid A in peritoneal macrophages.

Murine serum amyloid A1.1 (SAA1.1) has been conjugated with the fluorophore Texas Red (TxR), and its interaction with peritoneal macrophages has been visualized by scanning confocal microscopy. Binding of TxR-SAA to cell surfaces was inhibited by an excess of unlabelled SAA indicating the involvement of saturable receptors. Internalized TxR-SAA was seen initially as small punctate signals which in some cells evolved into a fine fluorescent network, a pattern typical of tubular endosomes. Colocalization of TxR-SAA with Cy5-labelled low density lipoprotein (LDL) but not with Oregon Green-labelled transferrin suggested that SAA trafficked through endosomes and lysosomes for degradation rather than through recycling compartments. Consistent with this catabolic pathway, macrophages loaded with TxR-SAA lost fluorescence within several days after being shifted to a fluorophore-free medium. In sharp contrast to this, cells maintained under amyloid-forming conditions, i.e. in the presence of unlabelled SAA and amyloid-enhancing factor (AEF) before and after treatment with TxR-SAA, remained brightly fluorescent over the course of 5 days. Immunocytochemistry verified the accumulation of SAA within macrophages. These findings support the hypothesis that a decreased catabolism of internalized SAA plays a role in AA amyloid pathogenesis.

Biochemical characterization of a neuroserpin variant associated with hereditary dementia.

Neuroserpin isolated from inclusion bodies in the brain of a patient with a neurodegenerative disease was characterized biochemically. The protein consisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was heterogeneous ending at residues 405, 407, 409, and 410. Arg was present at position 52. No normal Ser52 was found indicating that only mutant neuroserpin was present in the inclusion bodies. The three potential Asn glycosylation sites all contained carbohydrate. DNA sequence analysis of exons 2 to 9 of the neuroserpin gene in the proband showed the published normal neuroserpin sequence except for the presence of both adenine and cytosine at the first position of codon 52, that indicates heterozygosity for both the normal Ser(AGT) and variant Arg(CGT) at this position in the expressed protein. Restriction fragment length polymorphism analysis of a polymerase chain reaction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls were negative. Chemical characterization of the variant neuroserpin will significantly enhance the understanding of this protein in both normal physiology and neurodegenerative diseases.

Protein aging hypothesis of Alzheimer disease.

Alzheimer disease (AD), the most common form of aging-related neurodegenerative disorders, is associated with formation of fibrillar deposits of amyloid beta-protein (Abeta). While the direct involvement of Abeta in AD has been well documented, the relations between Abeta production, amyloid formation, and neurodegeneration remain unknown. We propose that AD is initiated by a protein aging-related structural transformation in soluble Abeta. We hypothesize that spontaneous chemical modification of aspartyl residues in Abeta to transient succinimide induces a non-native conformation in a fraction of soluble Abeta, rendering it amyloidogenic and neurotoxic. Conformationally altered Abeta is characterized by increased stability in solution and the presence of a non-native beta-turn that determines folding of Abeta in solution and the structure of Abeta subunits incorporated into amyloid fibrils. While the soluble 'non-native' Abeta is both the factor triggering the neurodegenerative cascade and the precursor of amyloid plaques, these two events result from interaction of Abeta with different sets of cellular components and need not coincide in space and time. Extensive literature data and experimental evidence are provided in support of this hypothesis.

Expression of SAA and amyloidogenesis in congenic mice of CE/J and C57BL/6 strains.

Inbred strains of mice display different susceptibilities to experimental induction of reactive amyloidosis. CBA/J, C57BL/6, and ICR are among the most susceptible strains, while CE/J mice appear to be totally resistant. In contrast to amyloidogenic strains which express two major acute phase serum amyloid A proteins (SAA1 and SAA2), CE/J mice produce only a single isoform, designated SAA2.2. Studies indicate that CE/J x CBA/J hybrid mice expressing both SAA2.2 and SAA1.1/SAA2.1 are amyloid resistant, and this has led to the hypothesis that SAA2.2 may protect mice against amyloid formation even in the presence of fibrillogenic SAA1.1. We have tested this hypothesis in mice derived from CE/J and C57BL/6 strains. CE/J mice were mated with C57BL/6 mice to produce F1 hybrids. Congenic mice were then produced by backcrossing each successive generation to C57BL/6 mice. Representative mice from F2 and F3 generations were analyzed to determine SAA genotype and susceptibility to amyloid induction by repeated casein injections. All F2 and F3 mice examined, including those which carried the SAA2.2 gene, developed extensive splenic AA amyloid. Expression of SAA2.2 in mice testing positive for the SAA2.2 gene was confirmed by sequence analysis of HDL-associated SAA proteins. These results demonstrate that the presence of SAA2.2 is not sufficient to protect CE/J x C57BL/6 hybrid mice from amyloid development. This is consistent with our observation that macrophage cultures, derived from C57BL/6, CBA/J, or CE/J mice, undergo amyloid deposition when treated with SAA1.1 alone or with equal amounts of SAA1.1 and SAA2.2, but show no deposition when treated solely with SAA2.2. We conclude from these studies that while SAA2.2 is non-fibrillogenic, its physical presence is not sufficient for protection against amyloid formation.

A cell culture system for the study of amyloid pathogenesis. Amyloid formation by peritoneal macrophages cultured with recombinant serum amyloid A.

A murine macrophage culture system that is both easy to employ and amenable to manipulation has been developed to study the cellular processes involved in AA amyloid formation. Amyloid deposition, as identified by Congo red-positive, green birefringent material, is achieved by providing cultures with recombinant serum amyloid A2 (rSAA2), a defined, readily produced, and highly amyloidogenic protein. In contrast to fibril formation, which can occur in vitro with very high concentrations of SAA and low pH, amyloid deposition in culture is dependent on metabolically active macrophages maintained in neutral pH medium containing rSAA2 at a concentration typical of that seen in acute phase serum. Although amyloid-enhancing factor is not required, its addition to culture medium results in larger and more numerous amyloid deposits. Amyloid formation in culture is accompanied by C-terminal processing of SAA and the generation of an 8.5-kd fragment analogous to amyloid A protein produced in vivo. Consistent with the possibility that impaired catabolism of SAA plays a role in AA amyloid pathogenesis, treatment of macrophages with pepstatin, an aspartic protease inhibitor, results in increased amyloid deposition. Finally, the amyloidogenicity exhibited by SAA proteins in macrophage cultures parallels that seen in vivo, eg, SAA2 is highly amyloidogenic, whereas CE/J SAA is nonamyloidogenic. The macrophage culture model presented here offers a new approach to the study of AA amyloid pathogenesis.

Identification of a novel substitution in the constant region of a gene coding for an amyloidogenic kappa1 light chain.

Current concepts regarding the association between immunoglobulin (Ig) light chain structure and AL amyloidosis (AL) emphasize Ig variable region amino acid substitutions because the majority of light chain amyloid fibrils that have been sequenced contain amino termini of the variable region with only small amounts of the constant region. In this report, we describe a patient with rapidly progressive AL whose amyloid deposits contained primarily monoclonal kappa light chain constant region fragments. We sequenced and analyzed this AL protein, determining that it was an O18-O8 kappa1 variant and that the constant region possessed an unusual Ser-->Asn substitution at position 177. Using pre-mortem bone marrow cells, we cloned and sequenced the cDNA for this AL protein (HCAK1) and, using DNA from post-mortem somatic tissue, we cloned and sequenced the patient's kappa germline O18-O8 donor and kappa constant region (Ckappa) gene segments. The cDNA that coded for HCAK1 contained a variable region that was derived from O18-O8, showing 96.1% homology to germline, and a Ckappa that had a nucleotide substitution (AGC to AAC), resulting in the 177Ser-->Asn replacement. Two Ckappa genes were cloned from somatic tissue DNA, one identical to a known Ckappa sequence and another containing this substitution which likely is a new Ckappa allotype. Our findings indicate that further investigation is warranted into the contributions genetic polymorphisms and light chain constant regions may make to amyloidogenesis.

Organ-specific (localized) synthesis of Ig light chain amyloid.

Ig amyloidosis is usually a systemic disease with multisystem involvement. However, in a significant number of cases amyloid deposition is limited to one specific organ. It has not been determined if the Ig light chain (LC) amyloid precursor protein in localized amyloidosis is synthesized by circulating plasma cells with targeting of the amyloid fibril-forming process to one specific organ, or whether the synthesis of Ig LC and fibril formation occurs entirely as a localized process. In the present study local synthesis of an amyloid fibril precursor LC was investigated. Amyloid fibrils were isolated from a ureter that was obstructed by extensive infiltration of the wall with amyloid. Amino acid sequence analysis of the isolated fibril subunit protein proved it to be derived from a lambdaII Ig LC. Plasma cells within the lesion stained positively with labeled anti-lambda Ab and by in situ hybridization using an oligonucleotide probe specific for lambda-LC mRNA. RT-PCR of mRNA extracted from the tumor and direct DNA sequencing gave the nucleotide sequence coding specifically for the lambdaII amyloid subunit protein, thus confirming local synthesis of the LC protein.

A novel apolipoprotein A-1 variant, Arg173Pro, associated with cardiac and cutaneous amyloidosis.

An American kindred was found to have hereditary amyloidosis with cutaneous and cardiac involvement. Characterization of fibrils isolated from skin identified the amyloid protein as the N-terminal 90 to 100 residues of apolipoprotein A-1. Sequence of the apolipoprotein A-1 gene was normal except for a G/C transversion at position 1638 which predicts an Arg to Pro substitution at residue 173. This mutation, unlike previously described amyloidogenic mutations is not in the N-terminal fragment which is incorporated into the fibril. The mutation is at the same residue as in apolipoprotein A-1 Milano (Arg173Cys) which does not result in amyloid formation. Decreased plasma HDL cholesterol levels in carriers of the Arg173Pro mutation suggest an increased rate of catabolism as has been shown for the amyloidogenic Gly26Arg mutation. This suggests that altered metabolism caused by the mutation may be a significant factor in apolipoprotein A-1 fibrillogenesis.

Hereditary amyloid cardiomyopathy caused by a variant apolipoprotein A1.

Autosomal dominant hereditary amyloidosis with a unique cutaneous and cardiac presentation and death from heart failure by the sixth or seventh decade was found to be associated with a previously unreported point mutation (thymine to cytosine, nt 1389) in exon 4 of the apolipoprotein A1 (apoA1) gene. The predicted substitution of proline for leucine at amino acid position 90 was confirmed by structural analysis of amyloid protein isolated from cardiac deposits of amyloid. The subunit protein is composed exclusively of NH2-terminal fragments of the variant apoA1 with the longest ending at residue 94 in the wild-type sequence. Amyloid fibrils derived from four previously described apoA1 variants are composed of similar fragments with carboxyl-terminal heterogeneity, but contrary to those variants, which all carry one extra positive charge, the substitution Leu90Pro does not result in any charge modification. It is unlikely, therefore, that amyloid fibril formation is related to change of charge for a specific residue of the precursor protein. This is in agreement with studies on transthyretin amyloidosis in which no unifying factor such as change of charge for amino acid residues has been noted.

Fibrinogen A alpha chain Leu 554: an African-American kindred with late onset renal amyloidosis.

An African-American kindred with renal amyloidosis is described. Four members in two generations developed nephropathy in the sixth to eighth decade of life. Kidney biopsy and subcutaneous fat aspirate biopsy of one patient revealed amyloid deposits. DNA analysis showed that patients were heterozygous for a mutation in the fibrinogen A alpha chain gene with a guanine to thymine transversion at the second base of codon 554, predicting a leucine for arginine substitution. Peptide sequence analysis of isolated plasma fibrinogen showed normal peptide as well as variant peptide with leucine replacing arginine at position 554, as predicted by the DNA sequence. The ratio between normal and variant peptides was approximately 1:1 in one patient and 3:2 in another. Although this African-American kindred has the exact same mutation as a previously described Peruvian-Mexican kindred, the onset age in this kindred is much later than in the Peruvian-Mexican kindred. This finding may indicate the existence of additional factor(s) beside the primary causative genetic mutation, which affect the expression of the disease.

Local synthesis of amyloid fibril precursor in AL amyloidosis of the urinary tract.

An amyloid tumor localized to the urethra was resected and shown by immunohistochemistry to contain fibril deposits that stained with antisera specific for lambda VI immunoglobulin light chain. The amino acid sequence of the fibril protein was homologous to lambda VI Positive staining of subepithelial plasma cells with lambda VI specific monoclonal antibody was consistent with the hypothesis that the fibril precursor light chain protein is synthesized and processed locally to give this type of localized amyloidosis.

A trinucleotide deletion in the transthyretin gene (delta V 122) in a kindred with familial amyloidotic polyneuropathy.

A 63-year-old white man of Ecuadorian origin had a subarachnoid hemorrhage at age 57 followed by numbness and paresthesia in his lower extremities. He subsequently developed sexual impotence, alternating constipation and diarrhea, urinary frequency, and difficulty in walking. Rectal biopsy revealed amyloid deposits immunohistochemically reactive with antitransthyretin antisera. Direct DNA sequencing of the transthyretin gene of the patient showed a trinucleotide deletion in exon 4. This deletion resulted in the loss of one of two valines at position 121 or 122. DNA analysis on 11 family members at risk revealed four mutant gene carriers. Plasma transthyretin levels in the mutant gene carriers measured by nephelometry were very low. Peptide sequence analysis revealed that most of plasma transthyretin was normal with only a small amount of variant protein. This is the first report of a DNA deletion in the transthyretin gene. We speculate that the loss of valine in the carboxyl terminal region of the transthyretin monomer alters stability of the tetrameric protein, which leads to rapid clearance from the plasma and amyloid deposition in the tissue.