DPP9 is a novel component of the N-end rule pathway targeting the tyrosine kinase Syk.
The aminopeptidase DPP9 removes dipeptides from N-termini of substrates having a proline or alanine in second position. Although linked to several pathways including cell survival and metabolism, the molecular mechanisms underlying these outcomes are poorly understood. We identified a novel interaction of DPP9 with Filamin A, which recruits DPP9 to Syk, a central kinase in B-cell signalling. Syk signalling can be terminated by degradation, requiring the ubiquitin E3 ligase Cbl. We show that DPP9 cleaves Syk to produce a neo N-terminus with serine in position 1. Pulse-chases combined with mutagenesis studies reveal that Ser1 strongly influences Syk stability. Furthermore, DPP9 silencing reduces Cbl interaction with Syk, suggesting that DPP9 processing is a prerequisite for Syk ubiquitination. Consistently, DPP9 inhibition stabilizes Syk, thereby modulating Syk signalling. Taken together, we demonstrate DPP9 as a negative regulator of Syk and conclude that DPP9 is a novel integral aminopeptidase of the N-end rule pathway.
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Daniela
D
Justa-Schuch
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Maria
M
Silva-Garcia
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Esther
E
Pilla
Institute of Cellular and Molecular Immunology, University Medical Center Goettingen, Goettingen, Germany.
Michael
M
Engelke
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Markus
M
Kilisch
Department of Bioanalytics, Institute of Clinical Chemistry, University Medical Center Goettingen, Goettingen, Germany.|Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Christof
http://orcid.org/0000-0002-0946-8166
C
Lenz
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Ulrike
U
Möller
Hematology Division, Department of Medicine, Harvard Medical School, Boston, United States.|Brigham and Women's Hospital, Boston, United States.
Fumihiko
F
Nakamura
Department of Bioanalytics, Institute of Clinical Chemistry, University Medical Center Goettingen, Goettingen, Germany.|Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Henning
H
Urlaub
Department of Molecular Biology, University Medical Center Goettingen, Goettingen, Germany.
Ruth
http://orcid.org/0000-0002-1720-3440
R
Geiss-Friedlander
B cell signalling; Cbl; DPP9; N-end rule; Syk; biochemistry; cell biology; human; protein half-life