MICROTUBULE-ASSOCIATED PROTEIN FUNCTION - LESSONS FROM EXPRESSION IN SPODOPTERA-FRUGIPERDA CELLS

The phenotypes induced by the expression of neuronal microtubule-assoc iated proteins (MAPs) in Sf9 cells have provided data on the in situ f unction of these proteins. Both MAP2 and tau can induce long processes in Sf9 cells, and the processes contain bundles of microtubules. In b oth cases the microtubules are aligned with their plus ends distal. Ta u expression usually induces a single process that is unbranched and o f uniform caliber. Processes can form even when the cells are grown in suspension. Microtubules do not extend all the way to the tip; instea d the terminal region contains an actin-rich meshwork. Taxol treatment of Sf9 cells also induces the assembly of microtubules into bundles b ut does not induce process formation in Sf9 cells. Therefore the in vi tro properties of tau as a molecule capable of assembling, stabilizing , and bundling microtubules do not fully account for the in vivo abili ty of tau alone to transduce microtubule assembly into a change in cel l shape. The morphological features of the processes induced by MAP2 d iffer in highly informative ways. (C) 1994 Wiley-Liss, Inc.