Cytoplasmic microtubules Microtubules are essential cytoskeletal polymers that are made of repeatingalpha/beta- Tubulin heterodimers and are present in all eukaryotic cells , , . Cytoplasmic microtubules are vital forintracellular trafficking of proteins, vesicles and organelles. They also affect cellshape and cell motility , , . All ofthese functions involve the interaction of microtubules with a large number ofmicrotubule-associated proteins ( MAP2, MAP4, Tau ), which areimportant for the regulation and distribution of microtubules in the cell, microtubuleassembly/disassembly and stability . Microtubules are highly dynamic andtheir dynamic instability is based on the binding and hydrolysis of GTP by tubulinsubunits. Only dimers with GTP can polymerize . Microtubule-associated molecular motors such as Kinesin s, Dynein s andMyosin s are involved in a variety of biological movements, e.g. axoplasmictransport and secretion , , . The Dynactin complex regulates protein trafficking, movement of lysosomes andendosomes and axonogenesis , , .