Expression and Localization of C-APP and N-APP in Peripheral Neurons of Rats and Crayfish After Axotomy

Nerve injury induces a cascade of molecular-cellular events, leading to neuronal death or survival, where amyloid precursor protein (APP) and its proteolytic products play an important role. We studied the localization and expression of C-APP and N-APP in rat dorsal root ganglia (DRG) with transected sciatic nerve, axotomized crayfish stretch receptor neuron (SRN) and ventral nerve cord (VNC) ganglia with transected connectives. C-APP and N-APP localized predominantly in neurons, not in glial cells. Axotomy increased C-APP and N-APP expression in rat and crayfish neurons. The expression of APP in crustaceans confirms its conservative nature. In DRG, C-APP level was higher in neuronal nuclei than in cytoplasm in 24 hours post-axotomy. N-APP accumulation was not observed in DRG and crayfish neuronal nuclei. SRN axotomy resulted in C-APP and N-APP accumulation in 4–8 hours in perikaryon and its extensions, but only С-APP accumulated in nuclei. This indicates that not the whole APP, but its C-terminal product, AICD, enters the nucleus. Also, there was high level of C-APP in SRN nucleolus, suggesting possible AICD involvement in rRNA synthesis and ribosome formation. The APP accumulation in transected axons confirms its involvement in injury-induced axonal events.

Mechanoreceptors and touch

“Mechanoreceptors and touch” is the fifth chapter of the book Sensory Transduction and describes general mechanisms of touch sensitivity in animals. It begins with a review of mechanoreception in the single-celled protozoan Paramecium and transduction of touch in the round worm Caenorhabditis elegans. A thorough treatment is next given of the crayfish stretch receptor and insect mechanoreceptors, including a description of NOMPC channels in Drosophila. The chapter then reviews the anatomy and physiology of mechanoreceptors and touch in mammals, both in glabrous and hairy skin. It concludes with recent discoveries of the molecular biology and physiology of Merkel cells, known to be responsible for much of mammalian touch sensation.