Dual targeting of cytochrome P4502B1 to endoplasmic reticulum and mitochondria involves a novel signal activation by cyclic AMP-dependent phosphorylation at Ser128

Hindupur K. Anandatheerthavarada, Gopa Biswas, Jayati Mullick, Naresh Babu V. Sepuri, Laszlo Otvos, Debkumar Pain, Narayan G. Avadhani

Research output: Contribution to journalArticlepeer-review

124 Scopus citations

Abstract

We have investigated mechanisms of mitochondrial targeting of the phenobarbital-inducible hepatic mitochondrial P450MT4, which cross-reacts with antibody to microsomal P4502B1. Results show that P4502B1 and P450MT4 have identical primary sequence but different levels of phosphorylation and secondary structure. We demonstrate that P4502B1 contains a chimeric mitochondrial and endoplasmic reticulum (ER) targeting signal at its N-terminus. Inducers of cAMP and protein kinase A-mediated phosphorylation of P4502B1 at Ser128 activate the signal for mitochondrial targeting and modulate its mitochondrial or ER destination. S128A mutation inhibits in vitro mitochondrial transport and also in vivo mitochondrial targeting in COS cells. A fragment of P4502B1 containing the N-terminal signal and the phosphorylation site could drive the transport of dihydrofolate reductase (DHFR) into mitochondria. Ser128 phosphorylation reduced the affinity of 2B1 protein for binding to SRP, but increased the affinity of the 2B1-DHFR fusion protein for binding to yeast mitochondrial translocase proteins, TOM40 and TIM44, and matrix Hsp70. We describe a novel regulatory mechanism by which cAMP modulates the targeting of a protein to two distinct organelles.

Original languageEnglish (US)
Pages (from-to)5494-5504
Number of pages11
JournalEMBO Journal
Volume18
Issue number20
DOIs
StatePublished - Oct 15 1999
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

Keywords

  • Chimeric signal
  • Mitochondrial targeting
  • P4502B1
  • Protein phosphorylation
  • cAMP

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