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Strenkert D, Schmollinger S, Paruthiyil S, Brown BC, Green S, Shafer CM, Salomé P, Nelson H, Blaby-Haas CE, Moseley JL, Merchant SS. Distinct function of Chlamydomonas CTRA-CTR transporters in Cu assimilation and intracellular mobilization. Metallomics 2024; 16:mfae013. [PMID: 38439674 PMCID: PMC10959442 DOI: 10.1093/mtomcs/mfae013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 03/02/2024] [Indexed: 03/06/2024]
Abstract
Successful acclimation to copper (Cu) deficiency involves a fine balance between Cu import and export. In the green alga Chlamydomonas reinhardtii, Cu import is dependent on a transcription factor, Copper Response Regulator 1 (CRR1), responsible for activating genes in Cu-deficient cells. Among CRR1 target genes are two Cu transporters belonging to the CTR/COPT gene family (CTR1 and CTR2) and a related soluble protein (CTR3). The ancestor of these green algal proteins was likely acquired from an ancient chytrid and contained conserved cysteine-rich domains (named the CTR-associated domains, CTRA) that are predicted to be involved in Cu acquisition. We show by reverse genetics that Chlamydomonas CTR1 and CTR2 are canonical Cu importers albeit with distinct affinities, while loss of CTR3 did not result in an observable phenotype under the conditions tested. Mutation of CTR1, but not CTR2, recapitulates the poor growth of crr1 in Cu-deficient medium, consistent with a dominant role for CTR1 in high-affinity Cu(I) uptake. On the other hand, the overaccumulation of Cu(I) (20 times the quota) in zinc (Zn) deficiency depends on CRR1 and both CTR1 and CTR2. CRR1-dependent activation of CTR gene expression needed for Cu over-accumulation can be bypassed by the provision of excess Cu in the growth medium. Over-accumulated Cu is sequestered into the acidocalcisome but can become remobilized by restoring Zn nutrition. This mobilization is also CRR1-dependent, and requires activation of CTR2 expression, again distinguishing CTR2 from CTR1 and consistent with the lower substrate affinity of CTR2. ONE SENTENCE SUMMARY Regulation of Cu uptake and sequestration by members of the CTR family of proteins in Chlamydomonas.
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Affiliation(s)
- Daniela Strenkert
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Stefan Schmollinger
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Srinand Paruthiyil
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Bonnie C Brown
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Sydnee Green
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Catherine M Shafer
- Molecular Toxicology Inter-departmental Ph.D. program, University of California, Los Angeles, CA 90095, USA
| | - Patrice Salomé
- Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA
| | - Hosea Nelson
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Crysten E Blaby-Haas
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jeffrey L Moseley
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Sabeeha S Merchant
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
- Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095, USA
- Department of Molecular and Cell Biology and Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Strenkert D, Schmollinger S, Paruthiyil S, Brown BC, Green S, Shafer CM, Salomé P, Nelson H, Blaby-Haas CE, Moseley JL, Merchant SS. Distinct function of Chlamydomonas CTRA-CTR transporters in Cu assimilation and intracellular mobilization. bioRxiv 2023:2023.10.19.563170. [PMID: 37905083 PMCID: PMC10614975 DOI: 10.1101/2023.10.19.563170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Successful acclimation to copper (Cu) deficiency involves a fine balance between Cu import and export. In the unicellular green alga Chlamydomonas reinhardtii , Cu import is dependent on C opper R esponse R egulator 1 (CRR1), the master regulator of Cu homeostasis. Among CRR1 target genes are two Cu transporters belonging to the CTR/COPT gene family ( CTR1 and CTR2 ) and a related soluble cysteine-rich protein (CTR3). The ancestor of these green algal proteins was likely acquired from an ancient chytrid and contained conserved cysteine-rich domains (named the CTR-associated domains, CTRA) that are predicted to be involved in Cu acquisition. We show by reverse genetics that Chlamydomonas CTR1 and CTR2 are canonical Cu importers albeit with distinct affinities, while loss of CTR3 did not result in an observable phenotype under the conditions tested. Mutation of CTR1 , but not CTR2 , recapitulate the poor growth of crr1 in Cu-deficient medium, consistent with a dominant role for CTR1 in high affinity Cu(I) uptake. Notably, the over-accumulation of Cu(I) in Zinc (Zn)-deficiency (20 times the quota) depends on CRR1 and both CTR1 and CTR2. CRR1-dependent activation of CTR gene expression needed for Cu over-accumulation can be bypassed by the provision of excess Cu in the growth medium. Over-accumulated Cu is sequestered into the acidocalcisome but can become remobilized by restoring Zn nutrition. This mobilization is also CRR1-dependent, and requires activation of CTR2 expression, again distinguishing CTR2 from CTR1 and is consistent with the lower substrate affinity of CTR2.
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Shafer CM, Tseng A, Allard P, McEvoy MM. Strength of Cu-efflux response in E. coli coordinates metal resistance in C. elegans and contributes to the severity of environmental toxicity. J Biol Chem 2021; 297:101060. [PMID: 34375643 PMCID: PMC8424214 DOI: 10.1016/j.jbc.2021.101060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 07/29/2021] [Accepted: 08/05/2021] [Indexed: 11/28/2022] Open
Abstract
Without effective homeostatic systems in place, excess copper (Cu) is universally toxic to organisms. While increased utilization of anthropogenic Cu in the environment has driven the diversification of Cu-resistance systems within enterobacteria, little research has focused on how this change in bacterial architecture impacts host organisms that need to maintain their own Cu homeostasis. Therefore, we utilized a simplified host–microbe system to determine whether the efficiency of one bacterial Cu-resistance system, increasing Cu-efflux capacity via the ubiquitous CusRS two-component system, contributes to the availability and subsequent toxicity of Cu in host Caenorhabditis elegans nematode. We found that a fully functional Cu-efflux system in bacteria increased the severity of Cu toxicity in host nematodes without increasing the C. elegans Cu-body burden. Instead, increased Cu toxicity in the host was associated with reduced expression of a protective metal stress-response gene, numr-1, in the posterior pharynx of nematodes where pharyngeal grinding breaks apart ingested bacteria before passing into the digestive tract. The spatial localization of numr-1 transgene activation and loss of bacterially dependent Cu-resistance in nematodes without an effective numr-1 response support the hypothesis that numr-1 is responsive to the bacterial Cu-efflux capacity. We propose that the bacterial Cu-efflux capacity acts as a robust spatial determinant for a host’s response to chronic Cu stress.
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Affiliation(s)
- Catherine M Shafer
- Molecular Toxicology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA
| | - Ashley Tseng
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA
| | - Patrick Allard
- Molecular Toxicology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA; Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA.
| | - Megan M McEvoy
- Molecular Toxicology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA; Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA; Department of Microbiology, Immunology and Molecular Genetics. University of California, Los Angeles, Los Angeles, CA.
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Abstract
Acivicin [(alphaS,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid] was investigated as an inhibitor of the triad glutamine amidotransferases, IGP synthase and GMP synthetase. Nucleophilic substitution of the chlorine atom in acivicin results in the formation of an imine-thioether adduct at the active site cysteine. Cys 77 was identified as the site of modification in the heterodimeric IGPS from Escherichia coli (HisHF) by tryptic digest and FABMS. Distinctions in the glutaminase domains of IGPS from E. coli, the bifunctional protein from Saccharomyces cerevisiae (HIS7), and E. coli GMPS were revealed by the differential rates of inactivation. While the ammonia-dependent turnover was unaffected by acivicin, the glutamine-dependent reaction was inhibited with unit stoichiometry. In analogy to the conditional glutaminase activity seen in IGPS and GMPS, the rates of inactivation were accelerated > or =25-fold when a nucleotide substrate (or analogue) was present. The specificity (k(inact)/K(i)app) for acivicin is on the same order of magnitude as the natural substrate glutamine in all three enzymes. The (alphaS,5R) diastereomer of acivicin was tested under identical conditions as acivicin and showed little inhibitory effect on the enzymes indicating that acivicin binds in the glutamine reactive site in a specific conformation. The data indicate that acivicin undergoes a glutamine amidotransferase mechanism-based covalent bond formation in the presence of nucleotide substrates or products. Acivicin and its (alphaS,5R) diastereomer were modeled in the glutaminase active site of GMPS and CPS to confirm that the binding orientation of the dihydroisoxazole ring is identical in all three triad glutamine amidotransferases. Stabilization of the imine-thioether intermediate by the oxyanion hole in triad glutamine amidotransferases appears to confer the high degree of specificity for acivicin inhibition and relates to a common mechanism for inactivation.
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Affiliation(s)
- S V Chittur
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-1333, USA
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