Stathmin is a ubiquitous, cytosolic 19-kDa protein, which is phosphorylated on up to four sites in response to many regulatory signals within cells. Its molecular characterization indicates a functional organization including an N-terminal regulatory domain that bears the phosphorylation sites, linked to a putative alpha-helical binding domain predicted to participate in coiled-coil, protein-protein interactions. In addtion to the protein kinases that phospjhorylate Stathmin such as CaMK, MAPK, p34cdc2, PKA, a few other proteins have been suggested to interact with stathmin in vivo. One of them was identified as BiP, a member of the hsp70 heat-shock protein family. Another is a previously unidentified, putative serine/threonine kinase, KIS, which might be regulated by stathmin or, more likely, be part of the kinases controlling its phosphorylation state. Finally, two proteins, CC1 and CC2, predicted to form alpha-helices participating in coiled-coil interacting structures. It has been also suggest that the action of antimicrotubule drugs can be affected by stathmin in at least two ways: (a) altered drug binding; and (b) growth arrest at the G2 to M boundary. Mutant p53 breast cancers exhibiting high levels of stathmin may be resistant to antimicrotubule agents.

Contributor: Kosi Gramatikoff, PhD

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