The distribution of gangliosides in subcellular fractions of guinea-pig cerebral cortex

Abstract

Gangliosides occurred mainly in the microsomal fraction of homogenates of guinea-pig cerebral cortex separated by usual differential-centrifuging techniques. Within the microsomal fraction gangliosides were associated with two groups of particles differing considerably in sedimenting properties. Ganglioside-rich particles were found in a subcellular fraction separating as a layer between 0.8 and 1.2 M-sucrose after equilibrium centrifuging in a density gradient. Ox-brain gangliosides added to homogenates were recovered almost completely from the nuclear fraction. Ultrasonic treatment of homogenates after removal of the nuclear fraction caused a shift in gangliosides to subcellular fractions containing smaller particles but did not solubilize them. Much less gangliosides were extracted after ultrasonic treatment of homogenates containing nuclei. The effect of added agents and various treatments to homogenates on the quantity of gangliosides extracted from particulate and supernatant fractions was studied. Addition of protamine or histone completely prevented the . extraction of gangliosides. A comparison of the affinity of subcellular fractions for basic proteins with the content of gangliosides was made. The fractions containing most of the tissue gangliosides showed the greatest affinity for basic proteins except a fraction rich in myelin fragments. The probable localization of gangliosides in cell membranes is discussed.