Altered Expression of M2, the Class II -Tubulin Isotype, in a Murine J774.2 Cell Line with a High Level of Taxol Resistance

doi:10.1074/jbc.270.52.31269

Altered Expression of M2, the Class II -Tubulin Isotype, in a Murine J774.2 Cell Line with a High Level of Taxol Resistance (*)

From the (1)Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 and the
(2)Children's Leukaemia and Cancer Research Centre, Prince of Wales Children's Hospital, High Street, Randwick, Sydney, New South Wales 2031, Australia

^¶To whom reprint requests should be addressed:
Dept. of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461.
Tel.: 718-430-2163; Fax: 718-430-8922.

Abstract

A series of taxol- and taxotere-resistant J774.2 cell lines has been characterized with respect to altered expression of β-tubulin, the cellular target for these drugs. Vertebrates have six classes of β-tubulin isotypes, each displaying a distinct pattern of expression. Although the functional significance of multiple β-tubulins has not been fully defined, there is evidence that the individual isotypes contribute to differences in microtubule dynamics and drug binding. To determine if alterations in the expression of β-tubulin isotypes play a role in taxol resistance, a PCR-based methodology was developed that permits highly specific amplification of each of the six known murine β-tubulin isotypes. Two isotypes, Mβ5 and Mβ3, were expressed abundantly in the drug-sensitive parental J774.2 cells. Although expressed at an extremely low level in the parental cells, expression of the Mβ2 isotype was increased 21-fold (<0.005) in the cell line most resistant to taxol. These findings suggest that a cell can alter its relative tubulin isotype composition in response to an external stress and specifically imply that altered expression of Mβ2, the class II β-tubulin isotype, may contribute to the development of high resistance to taxol.

Footnotes

↵^§ Supported by National Institute of General Medical Sciences Training Program in Pharmacological Sciences Grant 5T32 GM07260.
↵* This research was supported in part by United States Public Health Service Grants CA39821 and CA66183 and a Cancer Core Support Grant CA13330 (to S. B. H.), the National Health & Medical Research Council, Australia (to M. H. and M. D. N.), the Children's Leukaemia and Cancer Foundation Inc., Australia, and an International Union against Cancer Technology Transfer (ICRETT) Fellowship (to M. H.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵⁽¹⁾ The abbreviations used are:

PCR

polymerase chain reaction

UTR

untranslated region

MAP

microtubule-associated protein.
↵⁽²⁾ S. Lewis, personal communication.
↵⁽³⁾ N. Cowan and S. Lewis, personal communication.
↵⁽⁴⁾ S. Horwitz, unpublished observations.
↵⁽⁵⁾ S. Rao and S. Horwitz, unpublished observations.
- Received July 11, 1995.
- Revision received October 14, 1995.