Stathmin-1 (STMN1), also known as oncoprotein 18 (Op18), pp17, pp19, metablastin and LAP18, is a ubiquitously conserved phosphoprotein between all vertebrates. Stathmin is well known as a microtubule destabilizing protein (Sobel, Boutterin et al. 1989; Gavet, Ozon et al. 1998). STMN1 contains four phosphorylation sites on serine residues (Ser16, Ser25, Ser38 and Ser63), and these multiple phosphorylation sites suggest a regulatory role for it in regulation of various molecular reactions.
STMN1 shows binding activity to soluble free tubulin subunits with high affinity and this binding prevents molecular interaction of tubulins thereby inhibiting microtubule formation(Rubin and Atweh 2004). Additionally, stathmin is involved in microtubule disassembly with direct catastrophic reaction on microtubules chains (Howell, Deacon et al. 1999).
Microtubules, as important part of cytoskeleton, take part in a variety of cellular functions such as proliferation, cell differentiation, cell mobility, cell signalling, and intracellular transport of organelles. Additionally, a direct correlation between cytoskeleton biosynthesis and exocytosis machinery has been reported (Robinson, Guo et al. 1999; Valentijn, Valentijn et al. 1999; Martin-Verdeaux, Pombo et al. 2003). Cytochalasin D and latrunculin B, which are able to promote actin depolymerization, increase the exocytic response to antigen (Seagrave and Oliver 1990; Frigeri and Apgar 1999). Microtubule-dependent movement of exocytic vesicles has been documented in melanosomes and adipocytes (Fletcher, Welsh et al. 2000).
