Targeting of the c-Abl Tyrosine Kinase to Mitochondria in Endoplasmic Reticulum Stress-Induced Apoptosis

Abstract

The ubiquitously expressed c-Abl tyrosine kinase localizes to the nucleus and cytoplasm. Using confocal microscopy, we demonstrated that c-Abl colocalizes with the endoplasmic reticulum (ER)-associated protein grp78. Expression of c-Abl in the ER was confirmed by immunoelectron microscopy. Subcellular fractionation studies further indicate that over 20% of cellular c-Abl is detectable in the ER. The results also demonstrate that induction of ER stress with calcium ionophore A23187, brefeldin A, or tunicamycin is associated with translocation of ER-associated c-Abl to mitochondria. In concert with targeting of c-Abl to mitochondria, cytochrome c is released in the response to ER stress by a c-Abl-dependent mechanism, and ER stress-induced apoptosis is attenuated in c-Abl-deficient cells. These findings indicate that c-Abl is involved in signaling from the ER to mitochondria and thereby the apoptotic response to ER stress.

Cytoplasmic c-Abl provides a molecular ‘Rheostat’ controlling carcinoma cell survival and invasion

“…There is also accumulating evidence supporting a role for cytoplasmic Abl in mediating death. Mutant forms of Abl defective in DNA and Rb binding retain the ability to induce cell apoptosis, and cytoplasmic Abl promotes mitochondrial cytochrome c release and caspase 3 activation in response to oxidative stress (Sun et al, 2000;Ito et al, 2001). Our finding that H 2 O 2 strongly induces Crk phosphorylation and disassembly of Crk/CAS complexes in an Abl-dependent manner suggests that regulation of Crk/CAS coupling contributes to oxidative stress-induced apoptosis, possibly through downstream cytoskeletal effects including loss of cell attachment.…”

“…Cells were kept at 371C at 5% CO 2 . Cos 7 cells were transiently transfected using a standard lipofectamine protocol, as previously described (Ito et al, 2001). Mock-transfected cells were transfected as described above, using equivalent amounts of empty vector DNA.…”

Morphology of mitochondrial permeability transition: Morphometric volumetry in apoptotic cells

“…Four, of the drugs we have employed to induce apoptosis (listed in Table 1), staurosporine (Tafani et al, 2001), BFA (Ito et al, 2001), TNF (Vikhanskaya et al, 2002a), and camptothecin (Stefanis et al, 1999;Sanches-Alcazar et al, 2000) also promote the cytoplasmic release of cytochrome c.…”

Molecular mechanisms of cardiotoxicity of tyrosine kinase inhibition

“…The pathway linking ABL inhibition with the induction of ER stress is not clear. Several studies in fibroblasts suggest that a portion of the myristoylated form of ABL (ABL Ib) is localized to the ER, and participates in the activation of PKCδ and mitochondrial depolarization in the response to oxidants and ER stress 59,60 . However, ABL kinase activation was implicated in these processes, whereas inhibition of ABL activity triggers cardiomyocyte ER stress.…”