Novel regulation of chondroitin sulfate glycosaminoglycan modification of amyloid precursor protein and its homologue, APLP2.

Alzheimer's disease is characterized by the presence of parenchymal and cerebrovascular deposits of beta-amyloid (A beta). A beta is derived from larger amyloid precursor proteins (APP), a member of a family of related polypeptides that includes amyloid precursor-like proteins, APLP1 and APLP2. APP and APLP2 isoforms are encoded by several alternatively spliced APP and APLP2 transcripts, respectively. We previously reported that the APLP2-751 isoform is modified by the addition of chondroitin sulfate glycosaminoglycan (CS GAG) at Ser-614. In this report, we demonstrate that the APLP2-763 isoform, which contains an insertion of 12 amino acids immediately N-terminal to Ser-614, is not modified by CS GAG. Finally, we demonstrate that like APLP2-751, APP isoforms that lack sequences encoded by exon 15 (L-APP) are also modified by CS GAG, whereas APP forms containing exon 15 are not. We suggest that CS GAG modification of a subset of APP and APLP2 isoforms represents a means of generating functional diversity for these polypeptides.