A number of studies have examined the potential role of caspases in
neurotrophin withdrawal-induced neuronal cell death. In a seminal study,
Yuan and co-workers164 injected chicken dorsal root ganglion neurons with
a control vector or a vector containing a cDNA encoding crm A, a cowpox
virus polypeptide that selectively inhibits a number of different
caspases.22,165,166 Within 3 days of NGF withdrawal, ~80% of control neurons
exhibited apoptotic morphology, whereas only 25% of crmA-expressing neurons
were apoptotic.164 Expression of the baculovirus protein p35, another
caspase inhibitor,125 has likewise been shown to protect rat superior cervical
ganglion neurons from NGF withdrawal-induced apoptosis.167