Phosphorylation Enhances Mitochondrial Targeting of GSTA4-4 through Increased Affinity for Binding to Cytoplasmic Hsp70

Robin, Marie-Anne; Prabu, Subbuswamy K.; Raza, Haider; Anandatheerthavarada, Hindupur K.; Avadhani, Narayan G.

doi:10.1074/jbc.m301807200

Cited by 107 publications

(98 citation statements)

References 48 publications

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“…Bimodal targeting of CYPs and APP was facilitated by the N-terminal chimeric signal, which consists of a cryptic mitochondria-targeting signal immediately flanking the N-terminal ER-targeting signal. By contrast, a C-terminal cryptic mitochondria-targeting signal was critical for the mitochondrial translocation of cytosolic GSTs (21). We also showed that mitochondrial targeting of these proteins required the activation of a cryptic mitochondrial signal either by sequence-specific processing by a cytosolic endoprotease as in the case of CYP1A1 (14) or by PKA-mediated phosphorylation of Ser residues at positions 128 or 129 as in the case of CYP2B1 and CYP2E1 (16,18,23).…”

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confidence: 76%

“…In this study, we tested four different chimeric signals, including two N-terminally truncated forms to mimic endoproteolytic cleavage in the cytosol, as in the case of CYP1A1 (ϩ5/1A1 and ϩ33/1A1), and two that are targeted to mitochondria as intact uncleaved signals, namely CYP2B1 and CYP2E1 (15,16,18,21,23), for their ability to bind different TOM receptor proteins under both in vitro and in vivo conditions. Mitochondrial targeting of both CYP2B1 and 2E1 was enhanced markedly by PKA-mediated phosphorylation at the unique target sites, Ser-128 and Ser-129, respectively (16,18).…”

Section: Discussionmentioning

confidence: 99%

“…Our results showed that different CYPs, glutathione S-transferase (GST) isoforms, and the amyloid precursor protein (APP) are targeted to mitochondria in addition to their well established subcellular locations in the ER, cytosol, and plasma membranes, respectively (21,22). Bimodal targeting of CYPs and APP was facilitated by the N-terminal chimeric signal, which consists of a cryptic mitochondria-targeting signal immediately flanking the N-terminal ER-targeting signal.…”

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confidence: 91%

“…We also showed that mitochondrial targeting of these proteins required the activation of a cryptic mitochondrial signal either by sequence-specific processing by a cytosolic endoprotease as in the case of CYP1A1 (14) or by PKA-mediated phosphorylation of Ser residues at positions 128 or 129 as in the case of CYP2B1 and CYP2E1 (16,18,23). In contrast, phosphorylation of a tandem PKA/PKC (protein kinase C) tar-get site close to the C terminus was involved in the activation of the mitochondria-targeting signal of GSTA4-4 (21).…”

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confidence: 99%

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An Unusual TOM20/TOM22 Bypass Mechanism for the Mitochondrial Targeting of Cytochrome P450 Proteins Containing N-terminal Chimeric Signals

Anandatheerthavarada

Sepuri²,

Biswas³

et al. 2008

Journal of Biological Chemistry

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Previously we showed that xenobiotic-inducible cytochrome P450 (CYP) proteins are bimodally targeted to the endoplasmic reticulum and mitochondria. In the present study, we investigated the mechanism of delivery of chimeric signal-containing CYP proteins to the peripheral and channel-forming mitochondrial outer membrane translocases (TOMs). CYP؉33/1A1 and CYP2B1 did not require peripheral TOM70, TOM20, or TOM22 for translocation through the channel-forming TOM40 protein. In contrast, CYP؉5/1A1 and CYP2E1 were able to bypass TOM20 and TOM22 but required TOM70. CYP27, which contains a canonical cleavable mitochondrial signal, required all of the peripheral TOMs for its mitochondrial translocation. We investigated the underlying mechanisms of bypass of peripheral TOMs by CYPs with chimeric signals. The results suggested that interaction of CYPs with Hsp70, a cytosolic chaperone involved in the mitochondrial import, alone was sufficient for the recognition of chimeric signals by peripheral TOMs. However, sequential interaction of chimeric signal-containing CYPs with Hsp70 and Hsp90 resulted in the bypass of peripheral TOMs, whereas CYP27 interacted only with Hsp70 and was not able to bypass peripheral TOMs. Our results also show that delivery of chimeric signal-containing client proteins by Hsp90 required the cytosol-exposed N-terminal 143 amino acids of TOM40. TOM40 devoid of this domain was unable to bind CYP proteins. These results suggest that, compared with the unimodal mitochondria-targeting signals, the chimeric mitochondriatargeting signals are highly evolved and dynamic in nature.Protein targeting to different subcellular compartments is directed by specific N-terminal or internal signals, which serve as destination-specific mail delivery codes (1, 2). The signal sequences of proteins targeted to different membrane compartments, such as the endoplasmic reticulum (ER), 2 peroxisomes, and mitochondria, vary markedly in terms of amino acid sequence, hydrophobicity, and secondary structure and interact with distinctly different sets of carrier proteins, receptors, and protein translocator complexes (3-8). These observations have led to a widely accepted view that most protein targeting signals are unimodal in nature, which in turn restricts the destination of a given protein to a single subcellular compartment.ER-targeted proteins contain a distinct N-terminal hydrophobic signal for binding to a signal recognition particle, which in turn targets the emerging nascent chains to the ER (9). With certain exceptions (1, 10), ER targeting is thought to be cotranslational. Current models of protein targeting imply that the ER or mitochondrial destination of a protein is determined at the pretranslational level by virtue of the signal sequence that the protein carries. Many mitochondria-and ER-targeted proteins are encoded by a distinct set of genes. In a limited number of cases, characteristic mitochondrial targeting sequences are generated by differential expression of the gene using either alternate transcription/tr...

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confidence: 76%

Section: Discussionmentioning

confidence: 99%

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confidence: 91%

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confidence: 99%

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An Unusual TOM20/TOM22 Bypass Mechanism for the Mitochondrial Targeting of Cytochrome P450 Proteins Containing N-terminal Chimeric Signals

Anandatheerthavarada

Sepuri²,

Biswas³

et al. 2008

Journal of Biological Chemistry

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“…One possibility is that there is an increased mitochondrial targeting of ␣-synuclein protein during the pathogenesis of PD. In a series of previous studies we have reported an important role for post translation modifications in the mitochondrial targeting of a number of physiologically important proteins (16,17,19). We showed that mitochondrial targeting of CYP 2B1 and 2E1 requires protein kinase A-mediated phosphorylation of Ser residues at positions 128 or 129, respectively (16,17).…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial Import and Accumulation of α-Synuclein Impair Complex I in Human Dopaminergic Neuronal Cultures and Parkinson Disease Brain

Devi

Raghavendran

Prabhu

et al. 2008

Journal of Biological Chemistry

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956

926

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␣-Synuclein, a protein implicated in the pathogenesis of Parkinson disease (PD), is thought to affect mitochondrial functions, although the mechanisms of its action remain unclear. In this study we show that the N-terminal 32 amino acids of human ␣-synuclein contain cryptic mitochondrial targeting signal, which is important for mitochondrial targeting of ␣-synuclein. Mitochondrial imported ␣-synuclein is predominantly associated with the inner membrane. Accumulation of wild-type ␣-synuclein in the mitochondria of human dopaminergic neurons caused reduced mitochondrial complex I activity and increased production of reactive oxygen species. However, these defects occurred at an early time point in dopaminergic neurons expressing familial ␣-synuclein with A53T mutation as compared with wild-type ␣-synuclein. Importantly, ␣-synuclein that lacks mitochondrial targeting signal failed to target to the mitochondria and showed no detectable effect on complex I function. The PD relevance of these results was investigated using mitochondria of substantia nigra, striatum, and cerebellum of postmortem late-onset PD and normal human brains. Results showed the constitutive presence of ϳ14-kDa ␣-synuclein in the mitochondria of all three brain regions of normal subjects. Mitochondria of PD-vulnerable substantia nigra and striatum but not cerebellum from PD subjects showed significant accumulation of ␣-synuclein and decreased complex I activity. Analysis of mitochondria from PD brain and ␣-synuclein expressing dopaminergic neuronal cultures using blue native gel electrophoresis and immunocapture technique showed the association of ␣-synuclein with complex I. These results provide evidence that mitochondrial accumulated ␣-synuclein may interact with complex I and interfere with its functions. Parkinson disease (PD)2 is associated with the degeneration of dopaminergic neurons in the substantia nigra pars compacta.

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Glutathione‐Dependent Bioactivation

Lash

2007

CP Toxicology

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The classical view of the glutathione (GSH) conjugation pathway involves GSH S-transferase (GST)-dependent formation of thioether conjugates between GSH and an electrophilic substrate, processing to yield the corresponding cysteine S-conjugate, which is then converted to an N-acetylcysteine conjugate (or mercapturate). Mercapturates of most GST substrates are rendered more polar and thus readily excreted in urine. In contrast, there is a growing number of GST substrates that, rather than being detoxified, are bioactivated. These substrates include several halogenated solvents, many of which are nephrotoxic because of the tissue distribution of GSH conjugation pathway enzymes and membrane transporters, and prodrugs of certain chemotherapeutic agents. Although the initiating steps are the same regardless of whether the substrate is detoxified or bioactivated, the cysteine conjugate functions as a branch point. Bioactivated cysteine S-conjugates are metabolized in the kidneys by either cysteine conjugate β-lyase or flavin-containing monooxygenase to produce a reactive intermediate.

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Phosphorylation Enhances Mitochondrial Targeting of GSTA4-4 through Increased Affinity for Binding to Cytoplasmic Hsp70

Cited by 107 publications

References 48 publications

An Unusual TOM20/TOM22 Bypass Mechanism for the Mitochondrial Targeting of Cytochrome P450 Proteins Containing N-terminal Chimeric Signals

An Unusual TOM20/TOM22 Bypass Mechanism for the Mitochondrial Targeting of Cytochrome P450 Proteins Containing N-terminal Chimeric Signals

Mitochondrial Import and Accumulation of α-Synuclein Impair Complex I in Human Dopaminergic Neuronal Cultures and Parkinson Disease Brain

Glutathione‐Dependent Bioactivation

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