Expression of beta-amyloid precursor protein (APP) in human dorsal root ganglia

The present study reports the occurrence and localization of beta-amyloid precursor protein (APP) immunoreactivity (IR) in human lumbar dorsal root ganglia of healthy adult subjects (age range 25-43 years). To ascertain that ganglionic cells displayed APP IR, neurofilament (NFP) and S-100 proteins (S100P) were studied in parallel. Immunoblotting revealed four or five major proteins with apparent molecular masses between 100-125 kDa, which corresponded with the different full-length APP isoforms. Moreover, an additional protein of approximately 55 kDa was detected. Selective APP IR was observed restricted to the satellite glial cell cytoplasms whereas neuron cell bodies resulted unlabeled. Moreover, some intraganglionic nerve fibers also displayed APP IR, apparently labelling Schwann cells. No individual differences among subjects were observed neither in the pattern of APP IR distribution, nor in the intensity of APP IR. Although it remains to be demonstrated whether or not human primary sensory neurons express APP, present results strongly suggest that supporting glial cells may be a primary source of APP or any related peptide, at least in adult healthy people. The functional and clinical relevance of these findings, if any, remain to be clarified.