Journal of Neuroscience, Vol 6, 3103-3111, Copyright © 1986 by Society for Neuroscience
Distribution of calpains I and II in rat brain
T Hamakubo, R Kannagi, T Murachi and A Matus
Calpains I and II are calcium-dependent proteases that have been implicated
in several aspects of brain function, including neurofilament turnover,
Wallerian degeneration, and excitatory synaptic transmission. In this
study, specific affinity-purified antibodies against each of the enzymes
were used to determine their cellular distribution in rat brain.
Differences between the two were found throughout the brain, with calpain I
being located primarily in neurons, whereas calpain II was more prominent
in glial cells. In myelinated axons, calpain II was present at low levels
but calpain I was not detectable. In all brain areas, both enzymes were
concentrated in cell bodies, with lesser amounts in neuronal and glial
processes. Calpain I was only detectable proximally in dendrites and was
not found in spiny branchlets of either pyramidal or Purkinje cells. These
results suggest that calpain II is the likely form of the enzyme involved
in calcium-activated proteolytic phenomena in axons. They do not support
the existence of a role for calpain at excitatory axospinous synapses.