[PDF][PDF] Activated c-Abl is degraded by the ubiquitin-dependent proteasome pathway

A Echarri, AM Pendergast - Current Biology, 2001 - cell.com
A Echarri, AM Pendergast
Current Biology, 2001cell.com
C-Abl is a nonreceptor tyrosine kinase that is tightly regulated in the cell. Genetic data
derived from studies in flies and mice strongly support a role for Abl kinases in the regulation
of the cytoskeleton (reviewed in [1, 2]). C-Abl can be activated by several stimuli, including
oxidative stress [3], DNA damage [4], integrin engagement [5], growth factors, and Src family
kinases [6]. Structural alterations elicit constitutive activation of the c-Abl tyrosine kinase,
leading to oncogenic transformation. While the mechanisms that activate c-Abl are …
Abstract
C-Abl is a nonreceptor tyrosine kinase that is tightly regulated in the cell. Genetic data derived from studies in flies and mice strongly support a role for Abl kinases in the regulation of the cytoskeleton (reviewed in [1, 2]). C-Abl can be activated by several stimuli, including oxidative stress [3], DNA damage [4], integrin engagement [5], growth factors, and Src family kinases [6]. Structural alterations elicit constitutive activation of the c-Abl tyrosine kinase, leading to oncogenic transformation. While the mechanisms that activate c-Abl are beginning to be elucidated, little is known regarding the mechanisms that downregulate activated c-Abl. Here, we show for the first time that activated c-Abl is downregulated by the ubiquitin-dependent degradation pathway. Activated forms of c-Abl are more unstable than wild-type and kinase-inactive forms. Moreover, inhibition of the 26S proteasome leads to increased c-Abl levels in vitro and in cells, and activated c-Abl proteins are ubiquitinated in vivo. Significantly, inhibition of the 26S proteasome in fibroblasts increases the levels of tyrosine-phosphorylated, endogenous c-Abl. Our data suggest a novel mechanism for irreversible downregulation of activated c-Abl, which is critical to prevent the deleterious consequences of c-Abl hyperactivation in mitogenic and cytoskeletal pathways.
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