A study of cytokeratin profiles in localized cutaneous amyloids

Fibril structures of TFG protein mutants validate the identification of TFG as a disease-related amyloid protein by the IMPAcT method

We previously presented a bioinformatic method for identifying diseases that arise from a mutation in a protein's low-complexity domain that drives the protein into pathogenic amyloid fibrils. One protein so identified was the tropomyosin-receptor kinase-fused gene protein (TRK-fused gene protein or TFG). Mutations in TFG are associated with degenerative neurological conditions. Here, we present experimental evidence that confirms our prediction that these conditions are amyloid-related. We find that the low-complexity domain of TFG containing the disease-related mutations G269V or P285L forms amyloid fibrils, and we determine their structures using cryo-electron microscopy (cryo-EM). These structures are unmistakably amyloid in nature and confirm the propensity of the mutant TFG low-complexity domain to form amyloid fibrils. Also, despite resulting from a pathogenic mutation, the fibril structures bear some similarities to other amyloid structures that are thought to be nonpathogenic and even functional, but there are other factors that support these structures' relevance to disease, including an increased propensity to form amyloid compared with the wild-type sequence, structure-stabilizing influence from the mutant residues themselves, and double-protofilament amyloid cores. Our findings elucidate two potentially disease-relevant structures of a previously unknown amyloid and also show how the structural features of pathogenic amyloid fibrils may not conform to the features commonly associated with pathogenicity.

Keratinic amyloid deposition in canine hair follicle tumors

Keratinic primary localized cutaneous amyloidosis is a disease in humans; however, no similar condition has been reported in animals. This study aimed to investigate cutaneous keratinic amyloid deposition in dogs and elucidate its etiology. Canine hair follicle tumor tissues were histopathologically analyzed. Immunohistochemistry and mass spectrometry-based proteomic analyses were performed to identify precursor protein candidates. Structural prediction and in vitro fibrillization analyses were conducted to determine the amyloidogenic region and gene sequencing analysis was performed to assess mutations. Of the 266 samples, 16 had amyloid deposition. Amyloid deposits were found in the stroma of tumors and in the margins of keratin debris and around normal hair follicles. Cytokeratin 5 (CK5) was identified as a precursor protein candidate. C-terminal truncation of CK5 was observed in amyloid deposits, and the truncation sites varied depending on the deposition pattern. There was a significantly higher incidence of amyloid deposition in Shiba dogs, and CK5 amino acid polymorphisms were identified in these dogs. A part of the C-terminal region of both canine and human CK5 exhibited highly amyloidogenic properties in vitro. This study revealed the existence of cutaneous keratinic amyloid deposition in animals and identified CK5 as an amyloid precursor protein, providing novel insights into understanding the etiology of cutaneous amyloidosis.

Fibulin-4 accelerates amyloid formation through binding with a keratin 5 peptide fragment

Keratins are the major amyloid fibril component in localized cutaneous amyloidosis. We analyzed the amyloid components in the skin of patients with localized cutaneous amyloidosis by immunohistochemical staining using antisera against extracellular matrix proteins and keratin 5 (K5). Fibulin-4 and K5 colocalized in the amyloid deposits. Using 14 synthetic peptides, we screened for amyloidogenic sequences in the C-terminal region of K5, including the α-helical rod domain and the tail domain. Two peptides stained with thioflavin T possessed a β-sheet structure and formed amyloid-like fibrils. Among the amyloidogenic peptides, a peptide KT5-6 (YQELMNTKLALDVEIATYRKLLEGE) derived from the α-helical rod domain of K5 specifically bound to fibulin-4. In addition, amyloid formation of KT5-6 was accelerated by fibulin-4. These results suggest that degraded fragments of K5 containing the KT5-6 sequence form amyloid fibrils with fibulin-4. The data further suggest that degraded fragments of K5 and fibulin-4 have the potential to initiate cutaneous amyloidosis.

Comparison of Immunostaining with Hematoxylin-Eosin and Special Stains in the Diagnosis of Cutaneous Macular Amyloidosis

Background

Although macular amyloidosis is a relatively rare disease, it is a common cutaneous disease in Asia and the Middle East. On hematoxylin and eosin (H&E) stained slides, early lesions could easily be missed without the use of special stains and/or immunohistochemistry.

Methods

We enrolled 42 patients with the clinical impression of macular amyloidosis who had undergone two 4-mm punch biopsies from 2015 to 2016 at a dermatology clinic affiliated to Shiraz University. Besides, 14 cases with a clinical diagnosis other than macular amyloidosis were selected as the negative control group. Congo red, crystal violet, and immunohistochemical (IHC) staining of CK5 and high molecular weight keratin (HMWK) were performed for each specimen.

Results

H&E slides showed globular depositions in 15 (35.7%) out of 42 patients. None of the patients showed apple-green birefringence with Congo red stain. Evaluation of crystal violet stained sections revealed purplish violet amyloid deposits in 15 (35.7%) patients. IHC study showed expression of CK5 in 52.4% and HMWK in 50% of the patients, which was not a significant difference (p = 0.715). The findings of both IHC markers had a significant difference with H&E stains (p = 0.039) and crystal violet (p = 0.008). Additionally, we found that two punch biopsies from two sites in the involved area did not have a significant preference over one punch biopsy. All of the cases in the control group were negative for amyloid deposition in H&E, special stains, and IHC stained slides as expected.

Conclusions

IHC evaluation using CK5 and HMWK might be a useful tool for diagnosing macular amyloidosis.

Amyloid and hyaline globules in undifferentiated nasopharyngeal carcinoma

We characterize the clinicopathological features of two patients (one 38 year old woman and one 42 year old man, both of Chinese ethnicity) with Epstein Barr Virus positive non-keratinizing nasopharyngeal carcinoma from an endemic region with prominent presence of amyloid and one case with both amyloid and abundant intracytoplasmic hyaline globules. The amyloid material was positive for Congo red and showed apple green birefringence when examined under polarized light. The amyloid was immunoreactive for cytokeratins and was located both intra- and extracellularly. Frequently the amyloid had a light microscopical spherical appearance and displayed peripheral radiating fibrils from a central homogenous core. One of the patients had a unique presentation of nasopharyngeal carcinoma with perceived hemoptysis and coughing up two pieces of tumor tissue. In reality, the nasopharyngeal tumor was polypoid and the two fragments were pinched of from the main tumor mass.

Bilateral Limbal Keratin-Associated Amyloidosis

Conjunctival amyloid is usually of the immunoglobulin light chain (AL) variety. The authors report an exceptional case of bilateral limbal amyloid deposits that were identified by mass spectrometry as keratin-related specifically regarding to basal keratinocyte keratins 5 and 14. Cytokeratin-related amyloid has been described by immunohistochemical analysis of formalin-fixed cutaneous and mucous membrane lesions but not ocular tissues. The conjunctival lesion in the right eye contained intraepithelial dyskeratotic cells that extended to the surface, causing a lacy leukoplakia on clinical examination. The authors excluded the diagnosis of hereditary benign intraepithelial dyskeratosis in this patient. Collection of patient data and all protected patient health information was compliant with the Health Insurance Portability and Accountability Act.

Comparative proteomics analysis of primary cutaneous amyloidosis

Primary cutaneous amyloidosis (PCA) is a localized skin disorder that is characterized by the abnormal deposition of amyloid in the extracellular matrix (ECM) of the dermis. The pathogenesis of PCA is poorly understood. The objective of the present study was to survey proteome changes in PCA lesions in order to gain insight into the molecular basis and pathogenesis of PCA. Total protein from PCA lesions and normal skin tissue samples were extracted and analyzed using the isobaric tags for relative and absolute quantitation technique. The function of differentially expressed proteins in PCA were analyzed by gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interaction analysis. The proteins that were most upregulated in PCA lesions were further analyzed by immunohistochemistry. A total of 1,032 proteins were identified in PCA lesions and control skin samples, with 51 proteins differentially expressed in PCA lesions, of which 27 were upregulated. In PCA lesions, the upregulated proteins were primarily extracellulary located. In addition, GO analysis indicated that the upregulated proteins were significantly enriched in the biological processes of epidermal development, collagen fiber organization and response to wounding (adjusted P<0.001). KEGG analysis indicated that the upregulated proteins were significantly enriched in the signaling pathways of cell communication, ECM receptor interaction and focal adhesion (adjusted P<0.001). Furthermore, the upregulated proteins were enriched in the molecular function of calcium ion binding, and the calcium binding proteins calmodulin-like protein 5, S100 calcium-binding protein A7 (S100A7)/fatty-acid binding protein and S100A8/A9 exhibited the highest levels of upregulation in PCA. This analysis of differentially expressed proteins in PCA suggests that increased focal adhesion, differentiation and wound healing is associated with the pathogenesis of PCA.

Functional amyloids in the mouse sperm acrosome

The acrosomal matrix (AM) is an insoluble structure within the sperm acrosome that serves as a scaffold controlling the release of AM-associated proteins during the sperm acrosome reaction. The AM also interacts with the zona pellucida (ZP) that surrounds the oocyte, suggesting a remarkable stability that allows its survival despite being surrounded by proteolytic and hydrolytic enzymes released during the acrosome reaction. To date, the mechanism responsible for the stability of the AM is not known. Our studies demonstrate that amyloids are present within the sperm AM and contribute to the formation of an SDS- and formic-acid-resistant core. The AM core contained several known amyloidogenic proteins, as well as many proteins predicted to form amyloid, including several ZP binding proteins, suggesting a functional role for the amyloid core in sperm-ZP interactions. While stable at pH 3, at pH 7, the sperm AM rapidly destabilized. The pH-dependent dispersion of the AM correlated with a change in amyloid structure leading to a loss of mature forms and a gain of immature forms, suggesting that the reversal of amyloid is integral to AM dispersion.

Primary cutaneous amyloidosis of the glans penis. Two case reports and a review of the literature

BACKGROUND

Primary cutaneous amyloidosis of the penis is a rare entity.

OBJECTIVES

We describe two cases of primary penile cutaneous amyloidosis presenting as localized lesions on the penis and not associated with systemic amyloidosis.

METHODS

A comprehensive literature review of all published cases.

RESULTS

The rarest form of cutaneous amyloidosis, nodular amyloidosis, is the most frequent presentation of penis-limited cutaneous amyloid with a low incidence of systemic disease progression.

CONCLUSIONS

Although primary nodular amyloidosis is a rare entity it seems to be the most frequent presentation of penile-limited cutaneous disease, with a low incidence of systemic involvement.

Cutaneous amyloidosis: a concept review

Concepts and semantics are crucial for good communication between clinicians and pathologists. Amyloidosis was described more than 150 years ago. Therefore, the terminology related to it is abundant, varied, and sometimes complex. In this report, we intend to discuss several terms related to the disease, with special emphasis on cutaneous amyloidosis. We present a review, from Virchow to present, of the concepts related to amyloidosis: its nature, the classification of cutaneous forms of the disease, and the techniques used in its diagnosis.

Primary cutaneous amyloidosis of the external ear: a clinicopathological and immunohistochemical study of 17 cases

Primary cutaneous amyloidosis includes several forms of localized amyloidosis characterized by superficial amyloid deposits occurring at or near the dermal-epidermal junction in the absence of systemic involvement. Primary cutaneous amyloidosis of the auricular concha and external ear represents a rarely described variant. There have been 27 cases reported in the English language literature, and herein we report 17 additional cases. This article demonstrates that the amyloid observed in this context is generally positive for Congo red, crystal violet and thioflavin T. It also expresses cytokeratin 34ßE12 via immunohistochemistry. Our immunohistochemical results and review of the literature suggest that the amyloid in amyloidosis of the external ear is the result of basal keratinocyte degeneration and does not signify deposition from a systemic or generalized process.

Primary localized cutaneous amyloidosis intermingled with papulopustular lesions in a patient with Behçet's disease

Primary localized cutaneous amyloidosis (PLCA) sometimes shows overlapping with collagen vascular diseases; however, association with Behçet's disease (BD) is rare. We herein report a case of PLCA developing intermingled with papulopustular lesions associated with BD. A 57-year-old woman visited our hospital, complaining of recalcitrant multiple oral aphthae. Further detailed physical examination revealed folliculitis-like small pustules with surrounding erythema on the upper back. Also, she stated past histories of genital ulcers 10 years ago and erythema nodosum on the lower legs 4 years ago. A biopsy specimen from the pustular lesion on the back showed neutrophilic abscess in the epidermis with a number of perivascular inflammatory cells in the upper dermis. Congo-red and Dylon stain revealed amyloid deposition in the papillary dermis. Although association of systemic amyloidosis with BD is occasionally found in the literature, co-occurrence of cutaneous amyloidosis and papulopustular lesions of BD is extremely rare.

Ultrastructural analysis of amyloidoma

Amyloidomas are localized mass-forming deposits of amyloid that occur with or without association with systemic amyloidosis. The ultrastructural findings in 3 amyloidomas from 2 autopsy patients with primary systemic AL amyloidosis are described. By transmission electron microscopy, there were randomly oriented nonbranching fibrils showing some unusual curvilinear forms and considerable variability in fibril diameter (two subsets of fibrils, one 12-14 nm and another 28-30 nm in diameter). The larger fibrils showed features of microtubule formation. Scanning electron microscopy demonstrated complex 3-dimensional tangles of fibrils. These findings add to the current ultrastructural and morphologic spectrum of paraprotein deposition disease.

[Hereditary and non-hereditary cutaneous amyloidoses]

Amyloid and amyloidosis describes a heterogeneous group of diseases which are characterized by the pathological extracellular deposition of autologous proteins. Basically, amyloidoses can be divided into systemic or organ-limited (e.g. cutaneous) forms and can be acquired or hereditary in nature. The subclassification discriminates between primary amyloidosis (in the absence of an obvious predisposing disease) and secondary amyloidosis (if caused by a certain underlying disease). The subclassification of amyloidoses is based on the main protein constituent and therefore on the chemical composition of the amyloid fibrils. However, the exact etiopathogenesis of amyloid formation remains unclear. In addition to the clinical presentation, histology, electron microscopy and biochemical-immunological differentiation are also decisive for a proper diagnosis. In cutaneous amyloidosis the deposition of amyloid either occurs along reticulin fibers and the basal membrane (perireticulary amyloidoses) or along collagen fibers (pericollagenous amyloidosis). The purpose of this article is to provide an up-to-date overview on the different kinds of cutaneous amyloidoses.

Primary cutaneous amyloidosis of the auricular concha: case report and review of published work

A 70-year-old Japanese female developed tiny papules on her bilateral ears 2 years previously. A histological study of a biopsy specimen revealed that amorphous materials were present in the widened dermal papillae. Because these materials were positive for both Congo red and Dylon, we diagnosed the lesion as primary cutaneous amyloidosis of the auricular concha. Immunohistochemically, the amyloid substance stained positively with 34betaE12 (cytokeratin 1/5/10/14), suggesting that it had an epidermal origin. Seven reported cases of this unique disorder were also reviewed.

Keratin 16 Expression in Epidermal Melanocytes of Normal Human Skin

Although the prevailing dogma states that keratin filaments are the hallmark of keratinocytes and other epithelial cells, recent publications suggest that they may be expressed by a variety of normal and malignant cells of different embryonic origin. Keratin expression has been reported in fibroblasts and endothelial cells as well as in various sarcomas. Also, some human melanomas express keratins in addition to the traditional diagnostic markers of differentiation, such as S-100 and melanocyte-specific antigens. Many studies have shown that cultured cells obtained from various melanomas express keratin. Most recently, keratin expression has also been shown in cultured melanocytes of normal skin. We now report that normal human melanocytes in vivo express keratin 16 (K16) but not keratins 1, 5, 8, 10, 14, or even keratin 6, the type II partner that is normally expressed with K16 in keratinocytes. Similarly, melanocytes in vitro express K16 but not K6. Keratin 16 expression in vivo was present in basal melanocytes in specimens derived from donors (0-77 years) and from different anatomic locations, suggesting that keratin 16 is constitutively expressed by all melanocytes. It appears that keratin expression may be more prevalent than previously assumed, and that these cytoskeletal filaments may play important roles in tissues and cells other than epithelia.

Cytokeratin contents of basal cell carcinoma, epidermis overlying tumour, and associated stromal amyloidosis: an immunohistochemical study

Cytokeratins (CKs) are expressed specifically in the cytoplasm of epithelial cells. We investigated the expression of CKs immunohistochemically in basal cell carcinomas (BCCs), epidermis overlying tumour, and skin tumor-associated amyloidosis (STA). Twenty cases of BCC, 11 of which had STA were included to the study. The primary antibodies of CK1-8 (AE3), CK10 (DEK-10), CK14 (LL002), CK17 (E3), CK18 (DC10), CK19 (KS19.1), CK 5/6/18 (LP34), CK8/18 (5D3) were applied to the section immunohistochemically. In BCCs without STA, CK1-8, CK14 and CK17 antibodies were expressed by tumour tissue in all biopsy specimens. In the BCCs with STA, tumour tissue was immunoreactive always with CK1-8 and CK17 antibodies, and commonly immunoreactive with anti-CK 14 antibody. In the epidermis overlying tumour tissue, there was positive immunoreactivity with anti-CK 1-8, CK 5/6/18, CK 10 and CK 14 antibodies in all biopsy specimens. Anti-CK 17 antibody was also positive in 17 biopsy specimens. STA is immunoreactive with anti-CK1-8 in all specimens. There was mild staining with anti-CK5/6/18 and with anti-CK19 whereas no immunoreactivity with anti-CK10 and CK18 antibodies was found. In conclusion, we could not find a significant CK expression difference between BCCs with and without STA. Weak positivity and a few number of CKs were shown in STA when compared with those of BCC and epidermis overlying tumour tissue expressing the more variable CKs. Interestingly, although CKs coexpressed in pairs consisting of one basic and one acidic CK, we detected predominantly basic CKs in STA.