Shigeko Araki

Acidic sphingoglycolipids in invertebrate nervous tissue: Presence of several kinds of sphingophosphonoglycolipids in the nervous tissue of Aplysia kurodai, a sea gastropod

Several hitherto unknown sphingophosphonoglycolipids were identified in the lipid extract from the nervous tissue, nerve fibers and ganglia of Aplysia kurodai, which has only a small amount of gangliosides, if any. The most abundant sphingophosphonoglycolipids of the nerve fiber (FGL-VII) and ganglion (GGL-V) are ceramide bis(2-aminoethylphosphono)-pentaosides. Their oligosaccharide moieties consist of 1 mol each of glucose, 3-O-methylgalactose and galactosamine and 2 mol of galactose. Another main glycolipid (FGL-II) may be ceramide mono(2-aminoethylphosphono)-pentaoside which contains 1 mol each of glucose, galactosamine and fucose and 2 mol of galactose as its oligosaccharide moiety.

Glycolipids Isolated from Aplysia kurodaiCan Activate Cyclic Adenosine 3′, 5′‐Monophosphate‐Dependent Protein Kinase from Rat Brain

Abstract: Cyclic AMP (cAMP)‐dependent protein kinase (cAMP‐kinase) partially purified from the membrane fractions of rat brains was stimulated by novel phosphonogly‐cosphingolipids (glycolipids) derived from the skin and nerve fibers of Aplysia kurodai. Among various glycolipids tested, a major glycolipid from the skin, 3‐O‐MeGalβ 1→3GalNAcα 1→3 [6′‐O‐(2‐aminoethylphosphonyl) Galα1→2] (2‐aminoethylphosphonyl→6) Glcβ 1→4GICβ1→1ceramide (SGL‐II), was most potent, giving half‐maximal activation at 32.2 μM. Activation of cAMP‐kinase was maximal with 250 μM SGL‐II using kemptide as substrate. The effect of SGL‐II was additive on kinase activity at submaximal concentrations of cAMP. The kinase activity activated with SGL‐II was inhibited by the addition of protein kinase inhibitor peptide, a specific peptide inhibitor for cAMP‐kinase. Its inhibitory pattern was similar to that for the catalytic subunit. Of the various substrates tested, the glycolipid‐stimulated cAMP‐kinase could phosphorylate microtubule‐associated protein 2, synapsin I, and myelin basic protein but not histone H1 and casein. The regulatory subunit strongly inhibited the activity of purified catalytic subunit of cAMP‐kinase. This inhibition was reversed by addition of SGL‐II, as observed for cAMP. SGL‐II was capable of partially dissociating cAMP‐kinase, which was observed by gel filtration column chromatography. However, the binding activity of cAMP to the holoenzyme was not inhibited with SGL‐II. These results demonstrate that the glycolipids can directly activate cAMP‐kinase in a manner similar, but not identical, to that of cAMP.

Immunohistochemical localization of phosphonoglycosphingolipids in the nervous tissue ofAplysia

A group of novel phosphonoglycosphingolipids was isolated from the tissues of Aplysia. In the present experiment, antiserum was raised against total phosphonoglycosphingolipids isolated from the ganglia. This antiserum seems specific to the oligosaccharide moiety of the glycolipids. It did not react with gangliosides isolated from mammalian brain. Of the total phosphonoglycosphingolipids of the ganglion. GGL-V was strongly reactive, but GGL-I was hardly reactive with the antiserum. The indirect immunoperoxidase method in combination with light microscopy revealed staining of fibrous structures in the neuropil of ganglia, connective tracts and peripheral nerves. These fibrous structures often interconnected with supporting cells (glia cells). However, the neuron and its processes were stained not distinctly. Thus our results indicate that some of the major glycolipids isolated from the ganglion are mainly present in extraneuronal components in the nervous tissues of Aplysia.