Abeta immunoreactive material is present in several intracellular compartments in transfected, neuronally...

Processing of the amyloid beta-protein precursor is believed to play a critical role in the development of Alzheimer's disease neuropathology. The localization of the human Abeta epitope within mature neuroectodermally differentiated embryonal carcinoma (P19) cells, stably transfected with the cDNA coding for a wild form human amyloid beta-protein precursor (AbetaPP 751) was investigated. For this, we applied high resolution electron microscopy and immunocytochemistry with a newly developed, highly specfic monoclonal antibody (McSA1). We observed immunoreactive signals in a number of subcellular organelles such as early endosomes, the trans-Golgi network and in the dilated rough endoplasmic reticulum, but not in lysosomes. Occasionally Abeta immunoreactivity was associated with microtubules and filaments, with the outer mitochondrial membrane, and with the nuclear envelope. These observations expand on current data regarding intracellular trafficking of AbetaPP fragments and provoke further questions regarding the role of intracellular Abeta peptides in basal conditions and pathological states.