The current presence of a methionine residue within this peptide sequence is further confirmed with the observation of the peak using a 17.002 Da mass increment in the mutant peptide (m/z 1414.726, which corresponds towards the oxidation Harmaline from the methionine thioester. is certainly a conformational pathology seen as a the extracellular development of amyloid deposits and the progressive impairment of the peripheral nervous system. Point mutations in this tetrameric plasma protein decrease its stability and are linked to disease onset and progression. Since non-mutated transthyretin also forms amyloid in systemic senile amyloidosis and some mutation bearers are asymptomatic throughout their lives, non-genetic factors must also be involved in transthyretin amyloidosis. We discovered, using a differential proteomics approach, that extracellular chaperones such as fibrinogen, clusterin, haptoglobin, alpha-1-anti-trypsin and 2-macroglobulin are overrepresented in transthyretin amyloidosis. Our data shows that a complex network of extracellular chaperones are over represented in human plasma and we speculate that they act synergistically to cope with amyloid prone proteins. Proteostasis may thus be as important as point mutations in transthyretin amyloidosis. Introduction Transthyretin amyloidosis (ATTR) is an autosomal dominant degenerative disease characterized Harmaline by the formation of amyloid fibril deposits, mainly composed of Harmaline transthyretin (TTR), in different organs and tissues [1, 2]. These amyloid deposits hinder organ function, lead to their failure and, ultimately, death. ATTR has been associated, mainly by studies [3], with single amino acid substitutions in TTR, a plasma protein responsible for the transport of thyroxine and retinol in the blood, the latter via the association with the retinol-binding protein [4]. The only effective therapeutic option for ATTR is liver transplantation from cadaveric donors since plasma TTR is produced mainly in the liver. Moreover, domino liver transplant from ATTR patients, a practice recently introduced to obviate the shortage of livers available for transplantation, introduces TTR mutated forms in circulation, increasing the risk of ATTR development [5]. The main hypothesis for ATTR pathogenesis considers the tetramer instability favoring the dissociation to non-native monomeric species with the ability to self-associate. These soluble aggregates evolve to insoluble aggregates and amyloid fibers with the characteristic -cross sheet structure found in several neurodegenerative disorders such as Alzheimers and Parkinsons diseases [6]. This model, however, fails to explain two crucial aspects of amyloid formation. First, non-mutated TTR also forms amyloid, causing systemic senile amyloidosis [7]. Mutations only accelerate the intrinsic amyloidotic behavior of Harmaline this protein. Second, time to disease onset varies by decades for different patients bearing the same mutation, and individuals transplanted with liver from transthyretin amyloidotic individuals present an amyloidotic behavior much faster that individual bearing amyloidogenic mutations [8]. Discordant disease progression in homozygote twins From Sweden and Harmaline Spain was reported. In a case, one of the twins underwent liver transplantation, whereas the other is completely healthy, showing no symptoms 8 years after the onset of his brother disease [9, 10, 11]. It is also important to note that, homozygous ATTR V30M patients appear not to Pfkp develop a more aggressive disease than heterozygous ones [12]. Genetic factors alone do not explain all the process for amyloid formation and other factors should be taken in consideration. These questions point to the involvement of multiple factors in ATTR development. Moreover, several studies described structural transient states [13,14,15] during fibrillation that under the correct circumstances, do not further convert into amyloid fibrils [16,17]. Proteome analysis in different biological samples is being increasingly used for clinical diagnosis and identification of protein biomarkers for the disease onset of various pathologies. 2-DE is still a promising research area for markers discovery [18]: the most important advantage of plasma proteomics is the prospect of a noninvasive and easy sampling system of diagnosis, which might reduce the need of any kind of biopsy. The practical utility of 2-DE for studies of the high abundance plasma proteome has been substantial. Because the first dimension of the procedure (isoelectric focusing) is exquisitely sensitive to molecular charge and the second dimension (SDS.