Unfolded protein response-regulated Drosophila Fic (dFic) protein reversibly AMPylates BiP chaperone during endoplasmic reticulum homeostasis.
Drosophila Fic (dFic) mediates AMPylation, a covalent attachment of adenosine monophosphate (AMP) from ATP to hydroxyl side chains of protein substrates. Here, we identified the endoplasmic reticulum (ER) chaperone BiP as a substrate for dFic and mapped the modification site to Thr-366 within the ATPase domain. The level of AMPylated BiP in Drosophila S2 cells is high during homeostasis, whereas the level of AMPylated BiP decreases upon the accumulation of misfolded proteins in the ER. Both dFic and BiP are transcriptionally activated upon ER stress, supporting the role of dFic in the unfolded protein response pathway. The inactive conformation of BiP is the preferred substrate for dFic, thus endorsing a model whereby AMPylation regulates the function of BiP as a chaperone, allowing acute activation of BiP by deAMPylation during an ER stress response. These findings not only present the first substrate of eukaryotic AMPylator but also provide a target for regulating the unfolded protein response, an emerging avenue for cancer therapy.
From the Departments of Molecular Biology and.
Hyeilin
H
Ham
From the Departments of Molecular Biology and.
Andrew R
AR
Woolery
Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390.
Charles
C
Tracy
Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390.
Drew
D
Stenesen
Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390.
Helmut
H
Krämer
From the Departments of Molecular Biology and kim.orth@utsouthwestern.edu.
Kim
K
Orth
D000249:Adenosine Monophosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D002460:Cell Line; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D004331:Drosophila melanogaster / Q000201:enzymology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress; D050883:HSC70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006706:Homeostasis; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000737:chemistry / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D014158:Transcription, Genetic; D056811:Unfolded Protein Response; D015854:Up-Regulation
D029721:Drosophila Proteins; D050883:HSC70 Heat-Shock Proteins; C570457:Hsc70-3 protein, Drosophila; D000249:Adenosine Monophosphate; C574946:Fic protein, Drosophila; D009713:Nucleotidyltransferases
AMP; AMPylation; Adenosine; BiP; Chaperone; Drosophila; ER Stress; Unfolded Protein Response (UPR); grp78