Species-specific and heterogeneous distribution of sialoglycoconjugates in the primary olfactory center of three species of Asian salamanders (Cynops)

Sialic acids (Sia) are terminal components of glycoconjugates that are involved in molecular and cellular interactions in the olfactory system. Diverse glycoconjugates are expressed in the salamander olfactory projection; however, their sialylation and the linkage of Sia to underlying sugars remain largely unknown. The present study aimed to determine the expression of Sia linked to galactose (Gal)-N-acetylglucosamine and N-acetylgalactosamine (GalNAc) in the olfactory bulbs of three species of salamanders using lectin binding. Abundant distribution of sialoglycoconjugates was observed in the salamander olfactory bulb by lectins, Sambucus sieboldiana (SSA) and Maackia amurensis (MAM). Moreover, SSA and MAM showed heterogeneous bindings in the primary olfactory projection of Cynops pyrrhogaster and C. orientalis. Lectin reactivities obviously decreased in all layers of the olfactory bulb after sialidase digestion, indicating selective binding to sialoglycoconjugates. Next, we examined the expression of the subterminal sugar residues, Gal and GalNAc, after terminal Sia removal. Desialylation in the olfactory bulb enhanced the reactivity of Jacalin and Vicia villosa (VVA) lectins that recognize Gal and GalNAc respectively. Together with the binding of SSA and MAM, Sia linked to Gal and GalNAc might be a major component of sialoglycoconjugates in the salamander olfactory projection.

Keywords: Galactose; Glycoconjugate; Lectin; N-acetylgalactosamine; Olfactory bulb; Sialic acid.