Kunitomo, Hirofumi et al. (2015) International Worm Meeting "Dissecting the roles of primary interneurons that regulate memory-dependent salt concentration chemotaxis."

Kunitomo, Hirofumi, Satoh, Yohsuke, Iino, Yuichi, Sato, Hirofumi

[International Worm Meeting, 2015]

Mapping the neuronal components of perception, memory, and motor control is critical in understanding how memory-dependent behavior is encoded by the nervous system. Salt chemotaxis of Caenorhabditis elegans is a memory-dependent navigation behavior: animals are attracted to the salt concentration at which they have been fed, whereas they avoid it if they have been starved (salt concentration chemotaxis). The animals employ a biased random walk strategy (also called the pirouette strategy) to migrate towards preferred directions. In this strategy, the frequency of reorientation depends on the temporal change of salt concentration and this bias is modulated by the differences in salt concentration between the current environment and the memorized one. Interestingly, input from a single sensory neuron, ASER, is required and sufficient for salt concentration chemotaxis under well fed conditions, and ASER is activated by salt concentration decrease irrespective of cultivation salt concentrations. To understand how sensory inputs are translated into behavior, we examined the roles of postsynaptic neurons of ASER by ablating them individually or in combination. ASER densely synapses on three pairs of interneurons, AIA, AIB and AIY. Loss of AIY or mutations in ttx-3 resulted in impaired chemotaxis to low salt but not to high salt. On the other hand, AIA-ablated animals showed a weak but significant defect in chemotaxis to high salt. Ablating both AIY and AIA disrupted chemotaxis to both directions. Quantitative analyses of locomotion revealed that these chemotaxis defects were concomitant with altered properties of the pirouette strategy: upon salt concentration decreases, AIY-abated animals showed a defect in suppression of turning after cultivation at low salt, whereas AIA-ablated animals showed a defect in activation of turning after cultivation at high salt. Ablation of AIB interneurons did not cause discernible effect on salt concentration chemotaxis, although these neurons were involved in the regulation of ASER-evoked reorientation. These results indicate that although both AIY and AIA are involved in the regulation of turning frequency upon salt concentration decreases, they differently mediate transmission of sensory information after cultivation at distinct salt concentrations.

Hirabayashi J et al. (1992) J Biol Chem "Evidence that Caenorhabditis elegans 32-kDa beta-galactoside-binding protein is homologous to vertebrate beta-galactoside-binding lectins. cDNA cloning and deduced amino acid sequence."

Hirabayashi J, Satoh M, Kasai K-I

[J Biol Chem, 1992]

We have cloned a full-length cDNA for a beta-galactoside-binding protein with a relative molecular mass of 32 kDa (32-kDa GBP), recently purified from a nematode, Caenorhabditis elegans (Hirabayashi, J., Satoh, M., Ohyama, Y., and Kasai, K. (1992) J. Biochem. 111, 553-555). The clone contained a single open reading frame encoding 279 amino acids, including the initiator methionine. Significant sequence homology to metal-independent beta-galactoside-binding lectins (25-30% identities), which had previously been found only in vertebrates, was observed. Moreover, the nematode 32-kDa GBP proved to have a unique polypeptide architecture; that is, it is composed of two tandemly repeated homologous domains, each consisting of about 140 amino acids. The internal homology was about 32%. Thus, this protein is constructed with a duplicated fundamental unit which is similar to the subunit of vertebrate 14-kDa lectins. In spite of the extreme phylogenic distance between nematodes and vertebrates (divergence greater than 6 x 10(8) years ago), both of the two repeated domains of the nematode 32-kDa GBP retained most of the amino acid residues conserved in vertebrate lectins. This means that members of the metal-independent animal lectin family are distributed much more widely than had been believed: from nematodes to vertebrates. The implication is that proteins belonging to this family have fundamental roles which are not restricted to vertebrates but are common to almost all animals.

Arata Y et al. (1997) J Biol Chem "Structure of the 32-kDa galectin gene of the nematode Caenorhabditis elegans."

Hirabayashi J, Arata Y, Kasai K-I

[J Biol Chem, 1997]

Galectins are a family of soluble beta-galactoside-binding lectins distributed in both vertebrates and invertebrates and, more recently, found also in fungus. The 32-kDa galectin isolated from the nematode Caenorhabditis elegans (Hirabayashi, J., Satoh, M., and Kasai, K. (1992) J. Biol. Chem. 267, 15485-15490) was the first "tandem repeat-type" galectin, containing two homologous carbohydrate-binding sites. Here, we report the structure of the nematode 32-kDa galectin gene. Physical mapping by yeast artificial chromosome polytene filter hybridization revealed that the 32-kDa galectin gene is located on chromosome II. Analysis of the transcript (1.4 kilobases) showed the presence at its 5'-end of a 22-nucleotide trans-spliced leader sequence (SL1). The entire genomic structure spanning >5 kilobase pairs (kbp), including the 5'-noncoding region, two intervening sequences (introns 1 and 2), and the 3'-noncoding region, was completely determined by the combination of genomic polymerase chain reaction and conventional colony hybridization. Intron 1 was relatively long (2.4 kbp) and was found to be inserted after the ninth codon (TAC) from the initiation codon. This position proved to be almost homologous to the conserved first intron insertion position in the vertebrate galectin genes (i. e. genes of mammalian galectin-1, -2, and -3 and chick 14-kDa galectin). On the other hand, intron 2 was much shorter (0.6 kbp), and it was inserted into the central region of the second carbohydrate-binding site. Although such an insertion pattern has never been observed in the vertebrate galectin genes, it seems to be common in C. elegans tandem repeat-type galectin genes, as predicted by the C. elegans genome project (Coulson, A., and the C. elegans Genome Consortium (1996) Biochem. Soc. Trans. 24, 289-291). Based on extensive sequence comparison, the origin and molecular evolution of the tandem repeat-type galectins are discussed.

Hirabayashi J et al. (1996) J Biol Chem "Purification and molecular characterization of a novel 16-kDa galectin from the nematode Caenorhabditis elegans."

Kasai K-I, Ubukata T, Hirabayashi J

[J Biol Chem, 1996]

In our previous study (Hirabayashi, J., Satoh, M., Ohyama, Y., and Kasai, K. (1992) J. Biochem. (Tokyo) 111, 553-555), two beta-galactoside-binding lectins (apparent subunit molecular masses, 16 and 32 kDa, respectively) were identified in the nematode Caenorhabditis elegans. The subsequent study revealed that the 32-kDa lectin is a member of the galectin family. Since the 32-kDa galectin was found to consist of two homologous domains (similar to 16 kDa), 16-kDa lectin was thought to be a degradation product of the 32-kDa galectin. To clarify this, the 16-kDa lectin was purified by an improved procedure employing extraction with a calcium-supplemented buffer. The purified 16-kDa lectin was found to exist as a dimer (similar to 30 kDa) and showed hemagglutinating activity toward trypsinized rabbit erythrocytes, which was inhibited by lactose. Almost the whole sequence of the 16-kDa polypeptide (approximately 95%, 135 amino acids) was determined after digestion with various proteases. Based on the obtained information, a full-length cDNA was cloned with the aid of RNA-polymerase chain reaction. The clone encoded 146 amino acids including initiator methionine (calculated molecular mass, 15,928 Da). Based on these results, it was concluded that the 16-kDa lectin is a novel member of the galectin family, but not a degradation product of the 32-kDa galectin as had previously thought. However, the 16-kDa galectin showed relatively low sequence similarities to both the N-terminal and the C-terminal domains of the 32-kDa galectin (28% and 27% identities, respectively) and to various vertebrate galectins (14-27%). Nonetheless, all of the critical amino acids involved in carbohydrate binding were conserved. These observations suggest that, in spite of phylogenic distance between nematodes and vertebrates, both the 16-kDa and 32-kDa nematode isolectins have conserved essentially the same function(s) as those of vertebrate galectins, probably through recognition of a key disaccharide moiety,