Abstract
This chapter discusses biological functions of the amyloid β-protein precursor (APP). APP has evolved from being the precursor of a pathological peptide (Aβ) into a molecule with potentially diverse biological functions. The initial cloning of a cDNA encoding APP revealed primary structural homology to a single membrane-spanning cell surface receptor. In vitro translation studies with human, dog and rat brain polysomes followed by immunoprecipitation with domain-specific antipeptide antisera capable of differentiating between KPI-containing and KPI-lacking APP isoforms revealed significant differences in isoform expression patterns between these species. Examination of several peripheral tissues revealed APP immunoreactivity in ganglia and proximal nerves of the intestinal tract, adenohypophysis, dorsal root and trigeminal ganglia, cardiac muscle and megakaryocytes. Antibodies specific for the KPI-containing APP isoforms have been utilized to compare expression patterns in various tissues. Brain and cerebrospinal fluid (CSF) have been shown to contain soluble derivatives of APP isoforms, which both contain and lack the KPI domain. It is found that the neuroprotective activities of secreted APP isoforms, which apparently result from their ability to control intracellular calcium ion concentrations, are analogous to effects elicited by other neuronal growth factors, such as nerve growth factor and basic fibroblast growth factor.
Published Version
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