Amyloid/Melanin distinctive mark in invertebrate immunity

Protostomes and Deuterostomes show the same nexus between melanin production, and amyloid
fibril production, i.e., the presence of melanin is indissolubly linked to amyloid scaffold that, in turn, is
conditioned by the redox status/cytoplasmic pH modification, pro-protein cleavage presence,
adrenocorticotropin hormone (ACTH), melanocyte-stimulating hormone (α-MSH), and neutral
endopeptidase (NEP) overexpressions. These events represent the crucial component of immune
response in invertebrates, while in vertebrates these series of occurrences could be interpreted as a
modest and very restricted innate immune response. On the whole, it emerges that the mechanisms
involving amyloid fibrils/pigment synthesis in phylogenetically distant metazoan (viz, cnidaria,
molluscs, annelids, insects, ascidians and vertebrates) are evolutionary conserved. Furthermore, our
data show the relationship between immune and neuroendocrine systems in amyloid/melanin
synthesis. Indeed the process is closely associated to ACTH-α-MSH production, and their role in
stress responses leading to pigment production reflects and confirms again their ancient phylogeny.