Expression, characterization and ligand specificity of lipocalin-1 interacting membrane receptor (LIMR)

Abstract

Human lipocalin-1 interacting membrane receptor (LIMR) was the first lipocalin receptor to be identified, as a specific receptor for lipocalin-1 (Lcn1). Subsequently LIMR has been reported to interact with other ligands as well, notably with the bovine lipocalin β-lactoglobulin (BLG) and with the unrelated secretoglobin uteroglobin (UG). To study the ligand-binding behaviour of this prototypic lipocalin receptor in more detail, a system was developed for the recombinant expression of LIMR in Drosophila Schneider 2 (S2) cells, and for the subsequent solubilization and purification of the protein. The receptor forms dimers or larger oligomers when solubilized in n-dodecyl β-D-maltoside (DDM). The full-length, functional receptor was captured onto a surface plasmon resonance (SPR) chip via an α-V5 antibody, and the binding of various potential ligands was followed in time. In this way, LIMR was shown to be highly specific for Lcn1, binding the lipocalin with low micromolar to high nanomolar affinity. No interactions with any of the other putative ligands could be detected, raising doubts about the physiological relevance of the reported binding of BLG and UG to the receptor.

Keywords::

• Lipocalin-1
• tear lipocalin
• von Ebner's gland protein
• lipocalin receptor
• oligomeric state
• surface plasmon resonance
• receptor-ligand interaction

Acknowledgements

This work was funded by a Marie Curie Early Stage Training Fellowship from the European Community's Sixth Framework Program under contract MEST-CT-2004-007931-BIOMEM. We are very grateful to Berhard Redl (Department of Molecular Biology, University of Innsbruck, Austria) for providing the LIMR coding sequence.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.