CLONING AND IN-SITU LOCALIZATION OF A BRAIN-DERIVED PORIN THAT CONSTITUTES A LARGE-CONDUCTANCE ANION CHANNEL IN ASTROCYTIC PLASMA-MEMBRANES

We have cloned a protein from bovine brain, brain-derived voltage-depe ndent anion channel 1 (BR1-VDAC), that is identical to a recently sequ enced plasmalemmal-bound porin from human lymphocytes. mRNA hybridizat ion indicates that BR1-VDAC is widely distributed throughout nervous a nd nonnervous tissues. In situ localization substantiated that the BR1 -VDAC is associated with the plasmalemma of astrocytes. A monoclonal a ntibody that recognizes the N terminus of the BR1-VDAC protein complet ely blocks an astrocytic high-conductance anion channel that has elect rophysiological similarities with the mitochondrial VDAC. Since the hi gh-conductance anion channel in astrocytes has been shown to respond t o hypoosmotic solutions, its molecular identification provides the bas is for a better understanding of volume regulation in brain tissue.