Sequence of raccoon IAPP supports importance of a specific structural motif in the development of pancreatic islet amyloidosis

The amino acid sequence of raccoon islet amyloid polypeptide (IAPP), as predicted by analysis of polymerase chain reaction (PCR)-amplified sequences from genomic DNA, contains the same putative amyloidogenic sequence (GAILS) at residues 24-28 as human and cat IAPP. These findings are consistent with evidence that the occurrence of islet amyloidosis, usually in association with age-associated (type 2) diabetes, is limited to a few unique species (e.g., humans, cats, raccoons) that produce IAPP molecules containing an inherent amyloidogenic structural motif. Although the presence of an intrinsic amyloidogenic structural motif within the IAPP molecule appears to be a prerequisite for the development of this form of amyloidosis, it is increasingly clear that additional factors are importantly involved in the ultimate expression of IAPP fibrillogenesis and deposition as islet amyloid deposits.