Notable peer-reviewed articles–identification of amyloidogenic proteins (amyloidosis diagnostics) using MS-based proteomics methods.
Articles of note
Amyloidosis is a heterogeneous group of diseases caused by deposition of misfolded proteins, which usually leads to organ dysfunction. Accurate typing of amyloid deposits is of paramount importance because organ involvements and disease prognosis differ widely among different subtypes, and its treatments are type specific. Correct identification of amyloidogenic protein is crucial to proper treatment. Traditional antibody-based diagnostic methods such as immunohistochemistry and immunofluorescence are helpful in amyloid typing, but limitations of those approaches including antibody availability and serum protein contamination impair sensitivity and specificity of diagnosis. Learn more ›
Classification of amyloidosis by laser microdissection and mass spectrometry-based proteomic analysis in clinical biopsy specimens
The clinical management of amyloidosis is based on the treatment of the underlying etiology, and accurate identification of the protein causing the amyloidosis is of paramount importance. Current methods used for typing of amyloidosis such as immunohistochemistry have low specificity and sensitivity. In this study, we report the development of a highly specific and sensitive novel test for the typing of amyloidosis in routine clinical biopsy specimens. Our approach combines specific sampling by laser microdissection (LMD) and analytical power of tandem mass spectrometry (MS)-based proteomic analysis. We studied 50 cases of amyloidosis that were well-characterized by gold standard clinicopathologic criteria (training set) and an independent validation set comprising 41 cases of cardiac amyloidosis. Learn more ›
The human systemic (noncerebral) amyloidoses represent a heterogeneous group of disorders characterized by the widespread deposition of proteins as fibrils in organs or tissues throughout the body. The unequivocal identification of the type of amyloid deposited is critical to the correct diagnosis and treatment of patients with these illnesses. Heretofore, this information was inferred from clinical data, ancillary laboratory tests, and results of immunohistochemical, as well as genetic, analyses. However, to establish definitively the type of amyloid present, the chemical composition of the fibrillar components must be determined. Learn more ›
Amyloidoses are characterized by deposition of misfolded proteins as β-pleated sheet fibrils in organs. Despite the similar morphologic appearance of fibrils, at least 28 different proteins have been identified as causative agents of amyloidosis in humans, 14 of which responsible for systemic forms. Correct identification of the amyloidogenic proteins in each patient is crucial for clinical management, in order to avoid misdiagnosis, inappropriate treatment, and to assess the prognosis. Amyloidosis, being essentially a protein deposition disorder, is an attractive venue for the application of proteomics methodologies; among the different possible analytic goals, the most important is the unequivocal diagnosis and typing of the amyloid deposits. Learn more ›
Exploring the amyloid proteome in immunoglobulin-derived lymph node amyloidosis using laser microdissection/tandem mass spectrometry
Amyloidosis affecting lymph nodes (LN) may occur in the setting of systemic amyloidosis or as an entity localized to the site of production (peritumoral). Why some LN amyloid remains peritumoral is unknown. We speculated that the composition of amyloid in these two presentations differs. We analyzed the amyloid proteome in LN amyloid samples to identify differences between the systemic and peritumoral subtypes. In immunoglobulin-derived LN amyloidosis (N = 26), 70% had heavy chain amyloid (AH or mixed AH/AL). True localized LN amyloidosis was rare, with only 2 patients without a monoclonal protein component. Nineteen patients (73%) had typical amyloid syndromes (100% of AL vs 67% of AH/AL, P = 0.02). A trend to improved survival for the AH/AL group in comparison to AL (median 5-year survival 48 vs. 19 months, P = 0.06) was seen. Mass spectrometric amyloid analysis is a powerful tool for characterizing amyloid and may provide additional prognostic information. Learn more ›
Insights into the role of the beta-2 microglobulin D-strand in amyloid propensity revealed by mass spectrometry
In vivo beta-2 microglobulin (β2m) forms amyloid fibrils that are associated with the disease dialysis-related amyloidosis. Here, electrospray ionisation-ion mobility spectrometry-mass spectrometry has been used to compare the oligomers formed from wild-type β2m with those formed from a variant of the protein containing a single point mutation in the D strand, H51A, during in vitro fibril assembly. Using the amyloid-binding fluorescent dye, Thioflavin T, to monitor fibrillation kinetics, H51A was shown to exhibit a two-fold increase in the lag-time of fibril formation. Despite this, comparison of the oligomeric species observed during the lag-time of self-aggregation indicated that H51A had a higher population of oligomers, and formed oligomers of higher order, than wild-type β2m. Learn more ›
Laser microdissection and proteomic analysis of amyloidosis, cryoglobulinemic GN, fibrillary GN, and immunotactoid glomerulopathy
BACKGROUND AND OBJECTIVES: Organized deposits are present in amyloidosis, fibrillary GN, and immunotactoid glomerulopathy. However, the constituents of the deposits are not known.
DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Laser microdissection of glomeruli followed by mass spectrometry was performed to determine the composition of the deposits. The results were compared with cryoglobulinemic GN.
RESULTS: The results are divided into four major groups: amyloidogenic proteins, structural/other proteins, complement proteins, and Igs. With regards to amyloidogenic proteins, large spectra numbers of apolipoprotein E are noted in amyloidosis (41.8±20.9) compared with fibrillary (15.6±12.5) and immunotactoid (12.3±12) glomerulopathy. Learn more ›
Leukocyte cell-derived chemotaxin 2 (LECT2)-associated amyloidosis is a frequent cause of hepatic amyloidosis in the United States
Using laser microdissection and mass spectrometry (MS)-based proteomics, we subtyped amyloid deposits from 130 cases of hepatic amyloidosis. Although we confirmed that immunoglobulin light chain amyloidosis was the most frequent cause of hepatic amyloidosis, leukocyte cell-derived chemotaxin 2 (LECT2) amyloidosis (ALect2) accounted for 25% of cases. This novel finding was associated with Hispanic ancestry, incidental discovery of amyloid in liver specimens sampled for other unrelated conditions, and a characteristic pattern of hepatic amyloid deposition. Although ALect2 patients had a common LECT2 polymorphism, pathogenic mutations were not discovered, suggesting that constitutive or compensatory LECT2 overexpression led to ALect2 deposition. Learn more ›
On typing amyloidosis using immunohistochemistry. Detailled illustrations, review and a note on mass spectrometry
Every amyloid disease needs to be assessed for chemical composition of its amyloid because amyloid is pathogenetically diverse and each of the chemical amyloid types requires a different therapy. Basically four different approaches are being applied for typing of amyloid using immunohistochemistry, immunochemistry, mass spectrometry and chemistry. It is shown here how an easy immunohistochemical procedure has been developed over the years that can be used to classify specifically amyloid proteins for clinico-pathologic routine use. A larger number of tissues with chemically or immunochemically typed amyloids served as prototypes for developing a set of validated amyloid antibodies. Learn more ›
Shotgun proteomics technology has matured in the research laboratories and is poised to enter clinical laboratories. However, the road to this transition is sprinkled with major technical unknowns such as long-term stability of the platform, reproducibility of the technology and clinical utility over traditional antibody-based platforms. Further, regulatory bodies that oversee the clinical laboratory operations are unfamiliar with this new technology. As a result, diagnostic laboratories have avoided using shotgun proteomics for routine diagnostics. In this perspectives article, we describe the clinical implementation of a shotgun proteomics assay for amyloid subtyping, with a special emphasis on standardizing the platform for better quality control and earning clinical acceptance. Learn more ›