Recombinant production of the human aquaporins in the yeast Pichia pastoris (Invited Review)

Abstract

Aquaporins are water facilitating proteins embedded in the cellular membranes. Such channels have been identified in almost every living organism – including humans. These proteins are vital molecules and their malfunction can lead to several severe disorders and diseases. Hence, an increased understanding of their structure, function and regulation is of the utmost importance for developing current and future drugs. Heading towards this goal, the first problem to overcome is to acquire the proteins in sufficient amounts to enable functional and structural characterization. Using a suitable host organism, large amounts of target molecules can possibly be produced, but for membrane proteins limitations are frequently encountered. In the work described here, we have produced the 13 human aquaporins (hAQPs) in one of the most successful hosts for recombinant overproduction of eukaryotic proteins; the yeast Pichia pastoris, in order to explore the underlying bottleneck to a successful membrane protein production experiment. Here we present exceptional yield of hAQP1, whereas some other hAQPs were below the threshold needed for scaled up production. In the overproduction process, we have established methods for efficient production screening as well as for accurate determination of the initial production yield. Furthermore, we have optimized the yield of low producing targets, enabling studies of proteins previously out of reach, exemplified with hAQP4 as well as the homologue PfAQP. Taken together, our results. present insight into factors directing high production of eukaryotic membrane proteins together with suggestions on ways to optimize the recombinant production in the yeast P. pastoris.

Keywords::

• Aquaporin
• recombinant protein production
• integral membrane proteins
• Pichia pastoris

Acknowledgements

We would like to acknowledge Jennifer Carbrey (Duke University Medical Center) who kindly provided the cDNA for all hAQPs, William Skach (Oregon Health Sciences University) for providing rAQP4 cDNA and for sharing useful perspectives, the Proteomics Centre at Sahlgrenska Academy in Göteborg for perfoming the LC-MS/MS analysis and the Wallenberg Foundation for their support of the Membrane Protein Centre; Lundberg Laboratory, Göteborg, Sweden. Financial support: This work was supported by Swedish Science Research Council (VR), Carnegiestiftelsen, SWEGENE and financial support from the European Commission by contracts LSHG-CT-2004-504601 (E-MeP), LSHG-CT-2006-037793 (OptiCryst), HEALTH-F4-2007-201924 (EDICT), QLG2-CT-2002-00988 (SPINE) and LSHP-CT2004-012189 (MalariaPorin project) as well as the Marie Curie Training Network Aquaglyceroporins.

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