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Knock-in Mouse Lines Expressing Microsomal or Mitochondrial CYP1A1: Variations in Response to Oral Benzo[a]pyrene

Dong, Hongbin
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1245449157

Abstract Details

2009, PhD, University of Cincinnati, Medicine : Toxicology (Environmental Health).
In the past, CYP1A1 protein was known to be located in the endoplasmic reticulum (ER; microsomes). More recently, CYP1A1 was shown as well to be targeted to the inner mitochondrial membrane; mitochondrial import is dependent on NH2-terminal processing that exposes cryptic targeting signals. It is interesting that microsomal and mitochondrial CYP1A1 enzymes exhibit different electron donors, substrate specificities, and inducer properties. To understand the physiological and toxicological functions of microsomal versus mitochondrial CYP1A1, we generated three knock-in mouse lines by modifying the CYP1A1 NH2-terminal signal sequence. Cyp1a1(mtt/mtt) mice encode an NH2-terminal 31-amino acid truncated protein, deleting the entire ER-targeting signal domain and exposing the cryptic mitochondrial-targeting signal. Cyp1a1(mtp/mtp) mice encode a protein carrying L7N and L17N mutations; this mutant lacks the signal recognition particle (SRP)-binding site and subsequent ER-targeting, but requires cytosolic proteolysis for mitochondrial import. Cyp1a1(mc/mc) mice encode a microsomal protein having R34D and K39I mutations, which abolish the mitochondrial-targeting signals. After dioxin or beta-naphthoflavone treatment of these mouse lines, the CYP1A1 protein was shown to be located in the mitochondria of the Cyp1a1(mtp/mtp) and Cyp1a1(mtt/mtt) lines and in microsomes of the Cyp1a1(mc/mc) line. To test for differences in function, we compared the response to dietary benzo[a]pyrene (BaP). After 18 days of daily oral BaP treament, wild type and Cyp1a1(mc/mc) mice were completely protected, whereas Cyp1a1(-/-) and Cyp1a1(mtp/mtp) mice showed striking toxicity and compensatory up-regulation of CYP1A2 and CYP1B1 mRNA in several tissues. Our data support the likelihood that it is the microsomal rather than mitochondrial CYP1A1 enzyme that protects against dietary BaP toxicity. Such variation in functions of subcellular CYP1A1 isoforms may also exist under physiological conditions, given that these isoforms have distinct enzymatic properties in metabolizing endogenous substrates.
Daniel Nebert, MD (Committee Chair)
Howard Shertzer, MD (Committee Member)
Mary Beth Genter, PhD (Committee Member)
S. Steven Porrer, PhD (Committee Member)
122 p.
Toxicology
CYP1A1; mice; BaP; mtp/mtp; MT1A1; Avadhani

Recommended Citations

Citations

  • Dong, H. (2009). Knock-in Mouse Lines Expressing Microsomal or Mitochondrial CYP1A1: Variations in Response to Oral Benzo[a]pyrene [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1245449157

    APA Style (7th edition)

  • Dong, Hongbin. Knock-in Mouse Lines Expressing Microsomal or Mitochondrial CYP1A1: Variations in Response to Oral Benzo[a]pyrene. 2009. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1245449157.

    MLA Style (8th edition)

  • Dong, Hongbin. "Knock-in Mouse Lines Expressing Microsomal or Mitochondrial CYP1A1: Variations in Response to Oral Benzo[a]pyrene." Doctoral dissertation, University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1245449157

    Chicago Manual of Style (17th edition)

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© 2009, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.