Nuclear and cytoplasmic lectin receptor sites in rat Py1a osteoblasts

The intracellular distribution of lectin receptor sites was studied in the rat Pyla osteoblasts using immunofluorescence at the confocal microscopy le vel. This immortalized cell line was found to represent a satisfactory mode l to study the occurrence and distribution of sugar moieties. Our data show ed distinct affinity patterns of lectins recognizing different terminal or internal sugar residues. For some lectins, the binding patterns appeared to be cell cycle-independent, whereas for PNA the cell cycle greatly influenc ed the nuclear binding. By combining lectin affinity with sialidase degrada tion and alcoholic saponification the sialic acid acceptor sugars and deriv atives were also visualized. In particular, glycoconjugates with sialic aci ds linked to beta-galactose, and mainly C-4 acetylated, were located in the cytoplasm, while glycoconjugates characterized by sialic acids linked to a lpha-N-acetylgalactosamine, and devoid of acetyl groups at C-4, were almost exclusively found in the nucleus. The comparison of lectin affinities, wit h and without prior glycosidase digestions, allowed us to gain further insi ght into the chemical composition of glycoconjugates that act as the lectin receptor sites that appeared to belong to O- and N-linked glycoconjugates. The use of additional enzymatic treatments were useful to better establish the localization of nuclear receptor sites and results were compared with previous studies about endogenous and exogenous lectins in an attempt to re concile the association of lectins and sugars within the nucleus and their possible involvement in modulation of cell proliferation and/or response to chemical signals. The above digestions also provided information about the cytoplasmic binding patterns.