Nuclear magnetic resonance structure of the cytoplasmic tail of heparin binding EGF-like growth factor (proHB-EGF-CT) complexed with the ubiquitin homology domain of Bcl-2-associated athanogene 1 from Mus musculus (mBAG-1-UBH)

Biochemistry. 2014 Apr 1;53(12):1935-46. doi: 10.1021/bi5003019. Epub 2014 Mar 24.

Abstract

The membrane form of heparin binding EGF-like growth factor (proHB-EGF) yields secreted HB-EGF and a membrane-anchored cytoplasmic tail (proHB-EGF-CT), which may be targeted to the nuclear membrane after a shedding stimulus. Bcl-2-associated athanogene 1 (BAG-1) accumulates in the nuclei and inhibits apoptosis in adenoma-derived cell lines. The maintenance of high levels of nuclear BAG-1 enhances cell survival. However, the ubiquitin homology domain of BAG-1 from Mus musculus (mBAG-1-UBH) is proposed to interact with proHB-EGF-CT, and this interaction may enhance the cytoprotection against the apoptosis inducer. The mechanism of the synergistic anti-apoptosis function of proHB-EGF-CT and mBAG-1-UBH is still unknown. We offer a hypothesis that proHB-EGF-CT can maintain high levels of nuclear BAG-1. In this study, we first report the three-dimensional nuclear magnetic resonance structure of proHB-EGF-CT complexed with mBAG-1-UBH. In the structure of the complex, the residues in the C-terminus and one turn between β-strands β1 and β2 of mBAG-1-UBH bind to two terminals of proHB-EGF-CT, which folds into a loop with end-to-end contact. This end-to-end folding of proHB-EGF-CT causes the basic amino acids to colocalize and form a positively charged groove. The dominant forces in the binding interface between proHB-EGF-CT and mBAG-1-UBH are charge-charge interactions. On the basis of our mutagenesis results, the basic amino acid cluster in the N-terminus of proHB-EGF-CT is the crucial binding site for mBAG-1-UBH, whereas another basic amino acid in the C-terminus facilitates this interaction. Interestingly, the mBAG-1-UBH binding region on the proHB-EGF-CT peptide is also involved in the region found to be important for nuclear envelope targeting, supporting the hypothesis that proHB-EGF-CT is most likely able to trigger the nuclear translocation of BAG-1 in keeping its level high.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites / genetics
  • Cell Survival / genetics
  • Cytoplasm / chemistry
  • Cytoplasm / genetics
  • Cytoplasm / metabolism
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Genes, bcl-2
  • Heparin-binding EGF-like Growth Factor
  • Intercellular Signaling Peptides and Proteins / chemistry*
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Magnetic Resonance Spectroscopy* / methods
  • Mice
  • Molecular Sequence Data
  • Sequence Homology, Amino Acid
  • Transcription Factors / chemistry*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Ubiquitin / chemistry*
  • Ubiquitin / genetics
  • Ubiquitin / metabolism

Substances

  • BCL2-associated athanogene 1 protein
  • DNA-Binding Proteins
  • Hbegf protein, mouse
  • Heparin-binding EGF-like Growth Factor
  • Intercellular Signaling Peptides and Proteins
  • Transcription Factors
  • Ubiquitin