A ROLE FOR CYCLIN-DEPENDENT KINASE(S) IN THE MODULATION OF FAST ANTEROGRADE AXONAL-TRANSPORT - EFFECTS DEFINED BY OLOMOUCINE AND THE APC TUMOR-SUPPRESSOR PROTEIN

Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility w ere evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034-2844) reduced only anterograde movements, whereas APC2 (aa 1034-2130) or APC3 (aa 2 130-2844) reduced both anterograde and retrograde transport. NF1 had n o effect on organelle movement in either direction. Because APC contai ns multiple cyclin-dependent kinase (CDK) consensus phosphorylation mo tifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 mu M), it reduced retrograde movement were both affected at concentrations a t which other kinases are inhibited as well (50 mu M). Both anterograd e and retrograde transport also were inhibited by histone H1 and KSPXK peptides, substrates for proline-directed kinases, including CDKs. Ou r data suggest that CDK-like axonal kinases modulate fast anterograde transport and that other axonal kinases may be involved in modulating retrograde transport. The specific effect of APC4 on anterograde trans port suggests a model in which the binding of APC to microtubules may limit the activity of axonal CDK kinase or kinases in restricted domai ns, thereby affecting organelle transport.