Epitopes of gap junctional proteins localized to neuronal subsurface cisterns.

Several lines of evidence indicate the existence of channels that mediate the movement of calcium from the extracellular space directly into some intracellular calcium storage compartment and from one intracellular membrane-bounded compartment to another. The possibility that such channels resemble intercellular communication pathways formed by gap junction proteins (connexins) was investigated in rat brain. Antibodies against a rat liver gap junction protein (connexin32) were found to recognize several distinct proteins on Western blots of brain homogenates. In motoneurons these antibodies immunohistochemically labelled portions of neuronal endoplasmic reticulum membranes that form subsurface cisterns (SSCs) adjacent to the plasma membrane. These results suggest that SSCs and connexin-like proteins may be involved in the process of calcium mobilization in neurons.