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J. Cell Biol.,
Volume 139, Number 4, November 17, 1997 963-973
Cardiology Section of the Department of Medicine and the Department of Physiology, Gazes Cardiac Research Institute,
Medical University of South Carolina and the Veterans Administration Medical Center, Charleston, South Carolina 29401
Increased microtubule density, for which microtubule stabilization is one potential mechanism,
causes contractile dysfunction in cardiac hypertrophy.
After microtubule assembly, 
-tubulin undergoes two,
likely sequential, time-dependent posttranslational changes: reversible carboxy-terminal detyrosination
(Tyr-tubulin 
Glu-tubulin) and then irreversible deglutamination (Glu-tubulin 
2-tubulin), such that
Glu- and 2-tubulin are markers for long-lived, stable
microtubules. Therefore, we generated antibodies for
Tyr-, Glu-, and 2-tubulin and used them for staining
of right and left ventricular cardiocytes from control
cats and cats with right ventricular hypertrophy. Tyr-
tubulin microtubule staining was equal in right and left
ventricular cardiocytes of control cats, but Glu-tubulin
and 2-tubulin staining were insignificant, i.e., the microtubules were labile. However, Glu- and 2-tubulin
were conspicuous in microtubules of right ventricular
cardiocytes from pressure overloaded cats, i.e., the microtubules were stable. This finding was confirmed in
terms of increased microtubule drug and cold stability
in the hypertrophied cells. In further studies, we found
an increase in a microtubule binding protein, microtubule-associated protein 4, on both mRNA and protein
levels in pressure-hypertrophied myocardium. Thus,
microtubule stabilization, likely facilitated by binding
of a microtubule-associated protein, may be a mechanism for the increased microtubule density characteristic of pressure overload cardiac hypertrophy.
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