A novel tyrosine kinase-independent function of Drosophila abl correlates with proper subcellular localization

The axonal localization of the Drosophila abl protein and its genetic interactions with the disabled and fasciclin I genes implicate this cytoplasmic tyrosine kinase in the process of axonal pathfinding. Several changes at the amino terminus of abl permitted proper function and localization of the altered proteins. In contrast, the presence of human c-abl type 1a amino-terminal sequences or the murine c-abl carboxy-terminal domain interfered with function and axonal locallzation. Rescue of phenotypes caused by mutations in abl alone did not require tyrosine kinase activity, indicating a novel kinase-independent function for the properly localizaed abl protein. However, abl kinase activity was required to rescue the mutant phenotypes in genetic backgrounds also mutant for disabled.