ZNRF3/RNF43--A direct linkage of extracellular recognition and E3 ligase activity to modulate cell surface signalling.
The interactions of extracellular ligands with single membrane spanning receptors, such as kinases, typically serve to agonise or antagonise the intracellular activation of signalling pathways. Within the cell, E3 ligases can act to alter the localisation and activity of proteins involved in signalling systems. Structural and functional characterisation of two closely related single membrane spanning molecules, RNF43 and ZNRF3, has recently revealed the receptor-like functionalities of a ligand-binding ectodomain combined with the intracellular architecture and activity of an E3 ligase. This direct link provides a hereto novel mechanism for extracellular control of ubiquitin ligase activity that is used for the modulation of Wnt signalling, a pathway of major importance in embryogenesis, stem cell biology and cancer. In this review we discuss recent findings for the structure and interactions of the extracellular region of RNF43/ZNRF3 and draw parallels with the properties and function of signalling receptor ectodomains.
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Matthias
M
Zebisch
Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom. Electronic address: yvonne@strubi.ox.ac.uk.
E Yvonne
EY
Jones
D000595:Amino Acid Sequence; D000818:Animals; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*
D004268:DNA-Binding Proteins; D044767:Ubiquitin-Protein Ligases
LGR4/5/6; Rspondin; Transmembrane E3 RING ligase; Wnt signalling