Characterization of microtubule-associated proteins in teleosts

Although microtubules are known to play an important role in many cellular processes, they have been virtually neglected in fish. In this report, micr otubule-associated proteins (MAPs) in fish (teleost) were characterized usi ng antibodies (Abs) directed against the mammalian MAPs tau, MAP1A and B, a nd MAP2. Two different populations of tau-like proteins (TLPs) were found i n fish brain using the anti-tau Abs Tau-l, Tau-2, tau5', and tau3'. The TLP s that were recognized by Tau-l, Tau-2, and tau5' were (1) heat-stable; (2) the same molecular weight as mammalian TLPs: 59-62 kDa; (3) not enriched i n microtubules prepared from catfish brain; and (4) localized to the cell b ody of neurons in fish brains. While the TLPs recognized by tau3' Abs were (1) heat-stable; (2) lower molecular weight than mammalian TLPs: 32-55 vs. 50-65 kDa; (3) enriched in microtubule fractions prepared from catfish brai n, and (4) localized to the axons of neurons. These results are consistent with two different populations of TLPs being present in fish brains. While MAP:! was found to be approximately the same molecular weight, 250 kDa, in zebrafish and goldfish as in mammals and to be distributed to dendrites in the fish brain, both MAP1A and MAP1B were found to be about 25% the mass of their mammalian homologs. These results suggest that MAPS in fish have som e characteristics similar to their mammalian counterparts, but also possess some unique properties that: require further study to elucidate their func tion. (C) 1999 Wiley-Liss, Inc.