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14-3-3 sigma bound to bis-phosphorylated aminopeptidase N (APN, CD13) via canonical and non-canonical binding motifs
Structural highlights
Function1433S_HUMAN Adapter protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. Binds to a large number of partners, usually by recognition of a phosphoserine or phosphothreonine motif. Binding generally results in the modulation of the activity of the binding partner. When bound to KRT17, regulates protein synthesis and epithelial cell growth by stimulating Akt/mTOR pathway (By similarity). p53-regulated inhibitor of G2/M progression. Publication Abstract from PubMedAminopeptidase N (APN, CD13) is a trans-membrane ectopeptidase involved in many crucial cellular functions. Besides its role as a peptidase, APN also mediates signal transduction, and is involved in the activation of Matrix Metalloproteinases (MMPs). MMPs function in tissue remodeling within the extracellular space and are therefore involved in many human diseases such as fibrosis, rheumatoid arthritis, tumor angiogenesis and metastasis as well as viral infections. However, the exact mechanism that leads to APN driven MMP activation is unclear. It was previously shown that extracellular 14-3-3 adapter proteins binding APN induces the transcription of MMPs. As a first step, we sought to identify potential 1433 binding sites in the APN sequence. We constructed a set of phosphorylated peptides derived from APN to probe for interactions. We identified and characterized a canonical 14-3-3 binding site (site 1) within the flexible, structurally unresolved N-terminal APN region using direct binding Fluorescence Polarization (FP) assays and thermodynamic analysis (ITC). In addition, we identified a secondary, non-canonical binding site (site 2), which enhances the binding affinity in combination with site 1 by many orders of magnitude. Finally, we solved crystal structures of 1433sigma bound to mono- and bisphosphorylated APN derived peptides, which revealed atomic details of the binding mode of mono- and bivalent 14-3-3 interactions. Therefore, our findings shed some light on the first steps of APN-mediated MMP activation and opens the field for further investigation of this important signaling pathway. MMP activation associated Aminopeptidase N reveals a bivalent 14-3-3 binding motif.,Kiehstaller S, Ottmann C, Hennig S J Biol Chem. 2020 Oct 27. pii: RA120.014708. doi: 10.1074/jbc.RA120.014708. PMID:33109610[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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