| First Author | Robin MA | Year | 2003 |
| Journal | J Biol Chem | Volume | 278 |
| Issue | 21 | Pages | 18960-70 |
| PubMed ID | 12646569 | Mgi Jnum | J:83582 |
| Mgi Id | MGI:2662661 | Doi | 10.1074/jbc.M301807200 |
| Citation | Robin MA, et al. (2003) Phosphorylation enhances mitochondrial targeting of GSTA4-4 through increased affinity for binding to cytoplasmic Hsp70. J Biol Chem 278(21):18960-70 |
| abstractText | Recently we showed that three different isoforms of cytosolic glutathione S-transferases (GST), including GSTA4-4, are also localized in the mitochondrial compartment. In this study, we have investigated the mechanism of mouse GSTA4-4 targeting to mitochondria, using a combination of in vitro mitochondrial import assay and in vivo targeting in COS cells transfected with cDNA. Our results show that the mitochondrial GSTA4-4 is more heavily phosphorylated compared with its cytosolic counterpart. Protein kinase activators (cAMP, forskolin, or phorbol-12-myristate-13-acetate) markedly increased GSTA4-4 targeting to mitochondria, whereas kinase inhibitors caused its retention in the cytosol. Immunoinhibition and immunodepletion studies showed that the Hsp70 chaperone is required for the efficient translation of GSTA4-4 as well as its translocation to mitochondria. Co-immunoprecipitation studies showed that kinase inhibitors attenuate the affinity of GSTA4-4 for cytoplasmic Hsp70 suggesting the importance of phosphorylation for binding to the chaperone. Mutational analysis show that the putative mitochondrial targeting signal resides within the C-terminal 20 amino acid residues of the protein and that the targeting signal requires activation by phosphorylation at the C-terminal-most protein kinase A (PKA) site at Ser-189 or protein kinase C (PKC) site at Thr-193. We demonstrate for the first time that PKA and PKC modulate the cytoplasmic and mitochondrial pools of GSTA4-4. |
