Subcellular distribution of calponin and caldesmon in rat hippocampus

Caldesmon and calponin are two actin- and calmodulin-binding proteins involved in the ‘actin-linked’ regulation of smooth muscle and non-muscle Mg 2+-actin-activated myosin II ATPase activity. In the present report we show that caldesmon and calponin are present in the post-synaptic side of symmetric synapses and accumulate in the post-synaptic densities of asymmetric synapses. Caldesmon- and calponin-immunoreactivities are also observed at the plasma membrane of the hippocampal neurones. Finally, while caldesmon seems strictly distributed to neurones, acidic calponin is present in both neurones and astrocytes.