No abstract

Sialic acids play important roles in various biological functions. In the brain, evidence suggests that sialylation of glycoproteins and glycolipids affects neural plasticity. While the 18 sialyltransferase isoenzymes (STs) identi®ed to date synthesize individual sialyl-oligosaccharide structures, they each exhibit activity toward more than one substrate and can overlap in their speci®city. Therefore, the distribution of STs is a secondary factor in the study of speci®c sialylation. Here, seven STs; ST3Gal I2IV, ST8Sia IV, ST6Gal I and ST6Gal-NAc II, the expressions of which were identi®ed in the adult hippocampus by RT-PCR, showed diverse localization patterns in the hippocampus on in situ hybridization, suggesting that the individual cells expressed relevant STs. Furthermore, to assay activity-related changes in ST expression, we used amygdaloid-kindling among models of neural plasticity. Differential expression of the STs participating in the kindling, notably, up-regulation of ST3Gal IV and ST6GalNAc II mRNAs, and down-regulation of ST3Gal I and ST8Sia IV mRNAs, were observed in the hippocampus following kindled seizures. These results indicate that ST expressions are regulated by physiological activity and may play a role in neural plasticity. Keywords: epilepsy, hippocampus, in situ hybridization, neural plasticity, RT-PCR, sialyltransferase gene expression. Address correspondence and reprint requests to Keiko Kato, Division of Structural Cell Biology, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara, 630-0101, Japan. E-mail: kato@bs.aist-nara.ac.jp Abbreviations used: CMP, cytidine monophosphate; LTD, long-term depression; LTP, long-term potentiation; N-CAM, neural cell adhesion molecule; PSA, polysialic acid; ST, sialyltransferase isoenzyme; TLE, human temporal lobe epilepsy; UDP, uridine diphosphate; [the nomenclature of sialyltransferase isoenzyme is based on a previous report (Tsuji 1996)] ST3Gal I, Galb1,3GalNAc a-2,3-sialyltransferase (X73523); ST3Gal II, a different type of Galb1,3GalNAc a-2,3-sialyltransferase (X76989); ST3Gal III, Galb(1-3/1-4) GlcNAc a-2,3-sialyltransferase (X84234); ST3Gal IV, a different type of Galb(1-3/1-4) GlcNAc a2,3-sialyltransferase (D28941); ST8Sia IV, PST, N-glycan a-2,8-sialyltransferase (X86000); ST6Gal I, Galb1,4GlcNAc a-2,6-sialyltransferase (AB027197; homolog, to D16106); ST6GalNAc II, Galb1,3GalNAc-speci®c GalNAc a-2,6-sialyltransferase (AB027198; homolog to X93999). Brain areas: 1±6, layers 1±6 of the cerebral cortex; alv, alveus; CA123, sub®elds CA123 of Ammon's horn; cc, corpus callosum; cp, choroid plexus in lateral ventricle; DG, dentate gyrus; ®, ®mbria; G, granular layer of the dentate gyrus; h, hilus; Hb, habenular nucleus; LP, lateral posterior nucleus of thalamus; M, molecular layer of the dentate gyrus; p, polymorphic layer of the dentate gyrus; preS, presubiculum; ori, stratum oriens; rad, stratum radiatum; RS, retrosplenial cortex; S, subgranular zone of the dentate gyrus; sl-m, stratum lacunosum-moleculare; Th, ...

Amyotrophic lateral sclerosis (ALS) involves the progressive degeneration of motor neurons in the spinal cord and the motor cortex. It has been shown that 15–20% of patients with familial ALS (FALS) have defects in the Sod1 gene, which encodes Cu,Zn-superoxide dismutase (SOD). To elucidate the pathological role of mutated Cu,Zn-SOD, we examined the issue of whether mutated Cu,Zn-SOD affects the cell cycle. Mouse neuroblastoma Neuro-2a cells were transfected with human wild-type or mutated (G37R, G93A) Cu,Zn-SOD. Mutated, Cu,Zn-SOD-transfected cells exhibited marked retardation in cell growth and G2/M arrest. They also displayed lower reactivity to phalloidin, indicating that the cytoskeleton was disrupted. Immunoprecipitation, two-dimensional gel electrophoresis, and Western blot analysis indicated that mutated Cu,Zn-SOD associates with actin. Similar results were obtained by in vitro incubation experiments with purified actin and mutated Cu,Zn-SOD (G93A). These results suggest that mutated Cu,Zn-SOD in FALS causes cytoskeletal changes by associating with actin, which subsequently causes G2/M arrest and growth retardation.