title: Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins.
abstract: Plant development and architecture are greatly influenced by the polar distribution of the essential hormone auxin. The directional influx and efflux of auxin from plant cells depends primarily on AUX1/LAX, PIN, and ABCB/PGP/MDR families of auxin transport proteins. The functional analysis of these proteins has progressed rapidly within the last decade thanks to the establishment of heterologous auxin transport systems. Heterologous co-expression allowed also for the testing of protein-protein interactions involved in the regulation of transporters and identified relationships with members of the FK506-Binding Protein (FKBP) and cyclophilin protein families, which are best known in non-plant systems as cellular receptors for the immunosuppressant drugs, FK506 and cyclosporin A, respectively. Current evidence that such interactions affect membrane trafficking, and potentially the activity of auxin transporters is reviewed. We also propose that FKBPs andcyclophilins might integrate the action of auxin transport inhibitors, such as NPA, on members of the ABCB and PIN family, respectively. Finally, we outline open questions that might be useful for further elucidation of the role of immunophilins as regulators (servants) of auxin transporters (masters).
authors.affiliation: University of Fribourg, Department of Biology-Plant Biology, CH-1700 Fribourg, Switzerland. Electronic address: markus.geisler@unifr.ch.
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.affiliation: University of Zurich, Institute of Plant Biology, CH-8008 Zurich, Switzerland.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Bailly
authors.affiliation: Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR 97331, USA. Electronic address: ivanchem@science.oregonstate.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Ivanchenko
mesh_terms: D001692:Biological Transport; D021983:Cyclophilins / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D063245:Plant Development; D022021:Tacrolimus Binding Proteins / Q000378:metabolism*
chemical_list: D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D021983:Cyclophilins; D022021:Tacrolimus Binding Proteins
keywords: Auxin transport; Chaperon; Cyclophilins; FK506-binding protein (FKBP); Immunophilins; Protein–protein interaction