BACKGROUND: Alkaptonuria (AKU) is an ultra-rare inborn error of metabolism characterized by homogentisic acid (HGA) accumulation due to a deficient activity of the homogentisate 1.2-dioxygenase (HGD) enzyme. This leads to the production of dark pigments that are deposited onto connective tissues, a condition named 'ochronosis' and whose mechanisms are not completely clear. Recently, the potential role of hitherto unidentified proteins in the ochronotic process was hypothesized, and the presence of serum amyloid A (SAA) in alkaptonuric tissues was reported, allowing the classification of AKU as a novel secondary amyloidosis. METHODS: Gel electrophoresis, Western Blot, Congo Red- based assays and electron microscopy were used to investigate the effects of HGA on the aggregation and fibrillation propensity of amyloidogenic proteins and peptides [Aβ(1-42), transthyretin, atrial natriuretic peptide, α-synuclein and SAA]. LC/MS and in silico analyses were undertaken to identify possible binding sites for HGA (or its oxidative metabolite, a benzoquinone acetate or BQA) in SAA. RESULTS: We found that HGA might act as an amyloid aggregation enhancer in vitro for all the tested proteins and peptides in a time- and dose- dependent fashion, and identified a small crevice at the interface between two HGD subunits as a candidate binding site for HGA/BQA. CONCLUSIONS: HGA might be an important amyloid co- component playing significant roles in AKU amyloidosis. GENERAL SIGNIFICANCE: Our results provide a possible explanation for the clinically verified onset of amyloidotic processes in AKU and might lay the basis to setup proper pharmacological approaches to alkaptonuric ochronosis, which are still lacking.

Braconi, D., Millucci, L., Bernini, A., Spiga, O., Lupetti, P., Marzocchi, B., et al. (2017). Homogentisic acid induces aggregation and fibrillation of amyloidogenic proteins. BIOCHIMICA ET BIOPHYSICA ACTA. GENERAL SUBJECTS, 1861(2), 135-146 [10.1016/j.bbagen.2016.11.026].

Homogentisic acid induces aggregation and fibrillation of amyloidogenic proteins

BRACONI, DANIELA;MILLUCCI, LIA;BERNINI, ANDREA;SPIGA, OTTAVIA;LUPETTI, PIETRO;MARZOCCHI, BARBARA;NICCOLAI, NERI;BERNARDINI, GIULIA;SANTUCCI, ANNALISA
2017-01-01

Abstract

BACKGROUND: Alkaptonuria (AKU) is an ultra-rare inborn error of metabolism characterized by homogentisic acid (HGA) accumulation due to a deficient activity of the homogentisate 1.2-dioxygenase (HGD) enzyme. This leads to the production of dark pigments that are deposited onto connective tissues, a condition named 'ochronosis' and whose mechanisms are not completely clear. Recently, the potential role of hitherto unidentified proteins in the ochronotic process was hypothesized, and the presence of serum amyloid A (SAA) in alkaptonuric tissues was reported, allowing the classification of AKU as a novel secondary amyloidosis. METHODS: Gel electrophoresis, Western Blot, Congo Red- based assays and electron microscopy were used to investigate the effects of HGA on the aggregation and fibrillation propensity of amyloidogenic proteins and peptides [Aβ(1-42), transthyretin, atrial natriuretic peptide, α-synuclein and SAA]. LC/MS and in silico analyses were undertaken to identify possible binding sites for HGA (or its oxidative metabolite, a benzoquinone acetate or BQA) in SAA. RESULTS: We found that HGA might act as an amyloid aggregation enhancer in vitro for all the tested proteins and peptides in a time- and dose- dependent fashion, and identified a small crevice at the interface between two HGD subunits as a candidate binding site for HGA/BQA. CONCLUSIONS: HGA might be an important amyloid co- component playing significant roles in AKU amyloidosis. GENERAL SIGNIFICANCE: Our results provide a possible explanation for the clinically verified onset of amyloidotic processes in AKU and might lay the basis to setup proper pharmacological approaches to alkaptonuric ochronosis, which are still lacking.
2017
Braconi, D., Millucci, L., Bernini, A., Spiga, O., Lupetti, P., Marzocchi, B., et al. (2017). Homogentisic acid induces aggregation and fibrillation of amyloidogenic proteins. BIOCHIMICA ET BIOPHYSICA ACTA. GENERAL SUBJECTS, 1861(2), 135-146 [10.1016/j.bbagen.2016.11.026].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/1000037