J Biol Chem, Vol. 274, Issue 50, 35686-35692, December 10, 1999
The Microtubule Binding of Tau and High Molecular Weight Tau
in Apoptotic PC12 Cells Is Impaired because of Altered
Phosphorylation*
Penny K.
Davis and
Gail V. W.
Johnson
From the Departments of Pharmacology and Psychiatry, University of
Alabama at Birmingham, Birmingham, Alabama 35294-0017
Although the importance of the microtubule
network throughout cell life is well established, the dynamics of
microtubules during apoptosis, a regulated cell death process, is
unclear. In a previous study (Davis, P. K., and Johnson, G. V. (1999) Biochem. J. 340, 51-58) we demonstrated that the
phosphorylation of the microtubule-associated protein tau was increased
during neuronal PC12 cell apoptosis. The purpose of this study was to
determine whether the increased tau phosphorylation that occurred
during apoptosis impaired the microtubule binding capacity of tau. This study is the first demonstration that microtubule-binding by tau and
high molecular weight tau is significantly impaired as a result of
altered phosphorylation during a naturally occurring process, apoptosis. Furthermore, co-immunofluorescence studies reveal for the
first time that tau populations within an apoptotic neuronal PC12 cell
exhibit differential phosphorylation. In control PC12 cells, Tau-1
staining (Tau-1 recognizes an unphosphorylated epitope) is
evident throughout the entire cell body. In contrast, Tau-1 immunoreactivity in apoptotic PC12 cells is retained in the
nuclear/perinuclear region but is significantly decreased in the
cytoplasm up to the plasma membrane. The selective distribution of
phosphorylated tau in apoptotic PC12 cells indicates that tau likely
plays a significant role in the cytoskeletal changes that occur during apoptosis.
*
This work was supported by National Institutes of Health
Grant NS35060.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.