At axon initial segments and nodes of Ranvier in neurons, the spectrin membrane skeleton plays roles in physically stabilizing the plasma membrane integrity and in clustering voltage-gated sodium channels for proper conduction of the action potential. ␤IV-Spectrin, an essential component of the membrane skeleton at these sites, has an N-terminal-truncated isoform, ⌺6, which is expressed at much higher levels than the full-length isoform ⌺1. To investigate the role of ␤IV-spectrin ⌺6, we generated ⌺1-deficient mice with a normal level of ⌺6 expression (⌺1 ؊/؊ mice), and compared their phenotypes with those of previously generated mice lacking both ⌺1 and ⌺6 (⌺1⌺6 ؊/؊ mice). The gross neurological defects observed in ⌺1⌺6 ؊/؊ mice, such as hindleg contraction, were apparently ameliorated in ⌺1 ؊/؊ mice. At cellular levels, ⌺1⌺6 ؊/؊ and ⌺1 ؊/؊ neurons similarly exhibited waving and swelling of the plasma membrane at axon initial segments and nodes of Ranvier. By contrast, the levels of ankyrin G and voltage-gated sodium channels at these sites, which are significantly reduced in ⌺1⌺6 ؊/؊ mice, were substantially recovered in ⌺1 ؊/؊ mice. We conclude that the truncated ␤IV-spectrin isoform ⌺6 plays a specific role in clustering voltage-gated sodium channels, whereas it is dispensable for membrane stabilization at axon initial segments and nodes of Ranvier.The spectrin membrane skeleton is a polygonal cytoskeletal meshwork attached to the cytoplasmic face of the plasma membrane (1). The basic unit of the spectrin skeleton is a heterotetramer of two ␣-spectrin and two ␤-spectrin proteins. ␤-Spectrin has an N-terminal actin-binding domain, and the spectrin tetramers are bound to one another indirectly via short actin filaments to form the meshwork. ␤-Spectrin also binds to a membrane adaptor protein ankyrin via the spectrin repeat 15 (2), thereby allowing the attachment of the spectrin-actin meshwork to the plasma membrane. Two major roles are known for the spectrin skeleton. One is to physically stabilize the plasma membrane integrity. In hereditary diseases with mutations in the erythrocyte-specific ␣I-and ␤I-spectrin genes, the erythrocyte membrane becomes fragile, resulting in elliptocytosis and spherocytosis, and eventually hemolytic anemia (3). The second role is to cluster specific integral membrane proteins at high density in specialized regions of the plasma membrane. For example, ␣II-and ␤II-spectrins stabilize the clustering of Na ϩ /K ϩ -ATPase at cell-cell contact sites in polarized epithelial cells through ankyrin B-mediated interaction with Na ϩ /K ϩ

O-α-d-Rhamnopyranosyl-(1→3)-O-α-d-rhamnopyranosyl-(1→2)-d-rhamnopyranose, a repeating trisaccharide of the O-specific polysaccharides (OPSs) of Pseudomonades, and O-α-d-tyvelopyranosyl-(1→3)-O-α-d-mannopyranosyl-(1→4)-l-rhamnopyranose, a trisaccharide composing the OPSs of Salmonella typhi, were synthesized by in-situ activating glycosylation reactions using hemiacetal sugar derivatives. Allyl 2,4-di-O-benzyl-α-d-rhamnopyranoside was prepared via the direct ditritylation of allyl α-d-mannopyranoside. 3-O-Acetyl-2,4-di-O-benzyl-d-rhamnopyranose was used as a precursor for the moiety of d-tyvelose (3,6-dideoxy-d-arabino-hexose, 3,6-dideoxy-d-mannopyranose, 3-deoxy-d-rhamnose) of the salmonella trisaccharide.