Ultrastructural localization of fructose-1,6-bisphosphatase in mouse brain

Fructose-1,6-bisphosphatase has been studied in adult mouse brain of different ages using an antibody directed against the liver isoform. The presence of liver fructose-1,6-bisphosphatase in cerebellum, cerebral cortex, and hippocampus was assayed using Western blot and different immunocytochemical techniques. Immunocytochemistry with peroxidase reaction product was used to locate fructose-1,6-bisphosphatase in both neurons and astrocytes in the same areas, as well as in the rest of the brain, at light and electron microscope levels. Double immunofluorescence with neuronal or astrocytic markers confirmed the neuronal and astrocytic location of fructose-1,6-bisphosphatase in confocal microscope images. At the subcellular level, fructose-1,6-bisphosphatase was located in the nuclear and cytoplasmic compartments of both neurons and astrocytes, at all ages studied. Ultrastructurally, immunostaining appeared as small patches in the nucleus and the cytosol. In addition, immunostaining was present over the outer mitochondrial membrane, the plasma membrane, and the membranes of the rough endoplasmic reticulum and nuclear envelope, but not over Golgi membranes. In the neuropil fructose-1,6-bisphosphatase was located in dendritic spines, as well as in abundant astrocytic processes that, in some cases, surrounded immunopositive synapses. The possible role of fructose-1,6-bisphosphatase in neurons and astrocytes is discussed.