Immunolocalization of Kinetodesmal Fibers with an Anti-Laminin Antibody in Tetrahymena thermophila

Netrin, a protein in the laminin family, is a pleiotropic signal that guides axonal development as well as angiogenesis in animals. Axonal guidance via netrins is dependent upon the ability of netrin to act both as a chemorepellent and a chemoattractant, depending upon the cell type and the netrin concentration. Tetrahymena thermophila are unicellular eukaryotic protists that can sometimes be used as a model system for neurons, due to the fact that both are excitable cells. Our previous studies have shown that netrin-1-peptide, netrin-3-peptides, and netrin-4 are all chemorepellents in Tetrahymena, and that netrin-like proteins may be isolated from Tetrahymena by Western blotting. Because netrins are part of the laminin family, we used immunofluorescence to investigate whether an anti-laminin antibody would bind to proteins in Tetrahymena. We hypothesized that an anti-laminin antibody should colocalize with an anti-netrin-1 antibody. Instead, we found that our anti-laminin antibody preferentially stained kinetodesmal fibers on the cell membrane, suggesting a structural role for a laminin-like protein in Tetrahymena