Microtubule-targeting drugs induce bcl-2 phosphorylation and association with Pin1

• Published in: Neoplasia (New York, N.Y.) N.Y.), 2001-11, Vol.3 (6), p.550-559
• Main Authors: Pathan, N, Aime-Sempe, C, Kitada, S, Basu, A, Haldar, S, Reed, J C
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents - pharmacology; Apoptosis - drug effects; CDC2 Protein Kinase - metabolism; Cell Line - drug effects; Cell Line - metabolism; Enzyme Inhibitors - pharmacology; Erratum; Flavonoids - pharmacology; Humans; Imidazoles - pharmacology; Indoles - pharmacology; Jurkat Cells - drug effects; Jurkat Cells - metabolism; Kidney; Maleimides - pharmacology; Metaphase; Microtubules - drug effects; Mitosis - drug effects; Mutagenesis, Site-Directed; NIMA-Interacting Peptidylprolyl Isomerase; Nocodazole - pharmacology; Peptidylprolyl Isomerase - metabolism; Phosphorylation; Piperidines - pharmacology; Proline - chemistry; Protein Interaction Mapping; Protein Kinase Inhibitors; Protein Processing, Post-Translational - drug effects; Proto-Oncogene Proteins c-bcl-2 - metabolism; Pyridines - pharmacology; Structure-Activity Relationship; Transfection
• ISSN: 1522-8002; 1476-5586
• DOI: 10.1038/sj.neo.7900213

Bcl-2 is a critical suppressor of apoptosis that is overproduced in many types of cancer. Phosphorylation of the Bcl-2 protein is induced on serine residues in tumor cells arrested by microtubule-targeting drugs (paclitaxel, vincristine, nocodazole) and has been associated with inactivation of antiapoptotic function through an unknown mechanism. Comparison of a variety of pharmacological inhibitors of serine/threonine-specific protein kinases demonstrated that the cyclin-dependent kinase inhibitor, flavopiridol, selectively blocks Bcl-2 phosphorylation induced by antimicrotubule drugs. Bcl-2 could also be coimmunoprecipitated with the kinase Cdc2 in M-phase-arrested cells, suggesting that Cdc2 may be responsible for phosphorylation of Bcl-2 in cells treated with microtubule-targeting drugs. Examination of several serine-->alanine substitution mutants of Bcl-2 suggested that serine 70 and serine 87 represent major sites of Bcl-2 phosphorylation induced in response to microtubule-targeting drugs. Both these serines are within sequence contexts suitable for proline-directed kinases such as Cdc2. Phosphorylated Bcl-2 protein was discovered to associate in M-phase-arrested cells with Pin1, a mitotic peptidyl prolyl isomerase (PPIase) known to interact with substrates of Cdc2 during mitosis. In contrast, phosphorylation of Bcl-2 induced by microtubule-targeting drugs did not alter its ability to associate with Bcl-2 (homodimerization), Bax, BAG1, or other Bcl-2-binding proteins. Since the region in Bcl-2 containing serine 70 and serine 87 represents a proline-rich loop that has been associated with autorepression of its antiapoptotic activity, the discovery of Pin1 interactions with phosphorylated Bcl-2 raises the possibility that Pin1 alters the conformation of Bcl-2 and thereby modulates its function in cells arrested with antimicrotubule drugs.