Purification of human beta2-adrenergic receptor expressed in methylotrophic yeast Pichia pastoris

Production of a Human Histamine Receptor for NMR Spectroscopy in Aqueous Solutions

G protein-coupled receptors (GPCRs) bind a broad array of extracellular molecules and transmit intracellular signals that initiate physiological responses. The signal transduction functions of GPCRs are inherently related to their structural plasticity, which can be experimentally observed by spectroscopic techniques. Nuclear magnetic resonance (NMR) spectroscopy in particular is an especially advantageous method to study the dynamic behavior of GPCRs. The success of NMR studies critically relies on the production of functional GPCRs containing stable-isotope labeled probes, which remains a challenging endeavor for most human GPCRs. We report a protocol for the production of the human histamine H1 receptor (H1R) in the methylotrophic yeast Pichia pastoris for NMR experiments. Systematic evaluation of multiple expression parameters resulted in a ten-fold increase in the yield of expressed H1R over initial efforts in defined media. The expressed receptor could be purified to homogeneity and was found to respond to the addition of known H1R ligands. Two-dimensional transverse relaxation-optimized spectroscopy (TROSY) NMR spectra of stable-isotope labeled H1R show well-dispersed and resolved signals consistent with a properly folded protein, and 19F-NMR data register a response of the protein to differences in efficacies of bound ligands.

G protein-coupled receptors expressed and studied in yeast. The adenosine receptor as a prime example

G protein-coupled receptors (GPCRs) are the largest class of membrane proteins with around 800 members in the human genome/proteome. Extracellular signals such as hormones and neurotransmitters regulate various biological processes via GPCRs, with GPCRs being the bodily target of 30-40% of current drugs on the market. Complete identification and understanding of GPCR functionality will provide opportunities for novel drug discovery. Yeast expresses three different endogenous GPCRs regulating pheromone and sugar sensing, with the pheromone pathway offering perspectives for the characterization of heterologous GPCR signaling. Moreover, yeast offers a ''null" background for studies on mammalian GPCRs, including GPCR activation and signaling, ligand identification, and characterization of disease-related mutations. This review focuses on modifications of the yeast pheromone signaling pathway for functional GPCR studies, and on opportunities and usage of the yeast system as a platform for human GPCR studies. Finally, this review discusses in some further detail studies of adenosine receptors heterologously expressed in yeast, and what Geoff Burnstock thought of this approach.

GPCR drug discovery: integrating solution NMR data with crystal and cryo-EM structures

The 826 G protein-coupled receptors (GPCRs) in the human proteome regulate key physiological processes and thus have long been attractive drug targets. With the crystal structures of more than 50 different human GPCRs determined over the past decade, an initial platform for structure-based rational design has been established for drugs that target GPCRs, which is currently being augmented with cryo-electron microscopy (cryo-EM) structures of higher-order GPCR complexes. Nuclear magnetic resonance (NMR) spectroscopy in solution is one of the key approaches for expanding this platform with dynamic features, which can be accessed at physiological temperature and with minimal modification of the wild-type GPCR covalent structures. Here, we review strategies for the use of advanced biochemistry and NMR techniques with GPCRs, survey projects in which crystal or cryo-EM structures have been complemented with NMR investigations and discuss the impact of this integrative approach on GPCR biology and drug discovery.

Extrinsic Tryptophans as NMR Probes of Allosteric Coupling in Membrane Proteins: Application to the A2A Adenosine Receptor

Tryptophan indole 15N-1H signals are well separated in nuclear magnetic resonance (NMR) spectra of proteins. Assignment of the indole 15N-1H signals therefore enables one to obtain site-specific information on complex proteins in supramacromolecular systems, even when extensive assignment of backbone 15N-1H resonances is challenging. Here we exploit the unique indole 15N-1H chemical shift by introducing extrinsic tryptophan reporter residues at judiciously chosen locations in a membrane protein for increased coverage of structure and function by NMR. We demonstrate this approach with three variants of the human A2A adenosine receptor (A2AAR), a class A G protein-coupled receptor, each containing a single extrinsic tryptophan near the receptor intracellular surface, in helix V, VI, or VII, respectively. We show that the native A2AAR global protein fold and ligand binding activity are preserved in these A2AAR variants. The indole 15N-1H signals from the extrinsic tryptophan reporter residues show different responses to variable efficacy of drugs bound to the receptor orthosteric cavity, and the indole 15N-1H chemical shift of the tryptophan introduced at the intracellular end of helix VI is sensitive to conformational changes resulting from interactions with a polypeptide from the carboxy terminus of the GαS intracellular partner protein. Introducing extrinsic tryptophans into proteins in complex supramolecular systems thus opens new avenues for NMR investigations in solution.

Platform for the rapid construction and evaluation of GPCRs for crystallography in Saccharomyces cerevisiae

BACKGROUND

Recent successes in the determination of G-protein coupled receptor (GPCR) structures have relied on the ability of receptor variants to overcome difficulties in expression and purification. Therefore, the quick screening of functionally expressed stable receptor variants is vital.

RESULTS

We developed a platform using Saccharomyces cerevisiae for the rapid construction and evaluation of functional GPCR variants for structural studies. This platform enables us to perform a screening cycle from construction to evaluation of variants within 6-7 days. We firstly confirmed the functional expression of 25 full-length class A GPCRs in this platform. Then, in order to improve the expression level and stability, we generated and evaluated the variants of the four GPCRs (hADRB2, hCHRM2, hHRH1 and hNTSR1). These stabilized receptor variants improved both functional activity and monodispersity. Finally, the expression level of the stabilized hHRH1 in Pichia pastoris was improved up to 65 pmol/mg from negligible expression of the functional full-length receptor in S. cerevisiae at first screening. The stabilized hHRH1 was able to be purified for use in crystallization trials.

CONCLUSIONS

We demonstrated that the S. cerevisiae system should serve as an easy-to-handle and rapid platform for the construction and evaluation of GPCR variants. This platform can be a powerful prescreening method to identify a suitable GPCR variant for crystallography.

Characterization of Synonymous Codon Usage in the Newly Identified Duck Plague Virus UL16 Gene

A comparative analysis of the codon usage bias in the newly identified UL16 gene(GenBank accession no.EU195095) of DPV and the UL16 gene of 22 reference herpesviruses was performed. In this study, the synonymous codon usage bias of UL16 gene in the 23 herpesviruses have been analyzed and the results showed obvious differences by the CAI, RSCU, ENC and GC_3s. The results revealed that the synonymous codons with A and T at the third codon positon have widely usage in the codon of UL16 gene of DPV. The ENC-GC_3s plot revealed that the genetic heterogeneity in UL16 gene of herpesviruses was constrained by G+C content at the third codon position. The phylogenetic analysis suggested that DPV was evolutionarily closer to herpesviruses which further clustered into Alphaherpesvirinae. Furthermore the ORF of DPV UL16 gene has sequential rare codons. There were 21 codons showing distinct usage differences between DPV with Escherichia coli, 19 codons showing distinct usage differences between DPV with yeast, and 20 between DPV and Human. Therefore the Escherichia coli, Yeast and Human expression system were suitable for the expression of DPV UL16 gene if some codons could be optimized.

Characterization of Codon Usage Bias in UL21gene from Duck Enteritis Virus

In this paper, the comprehensive analysis of codon usage bias of Duck enteritis virus (DEV) UL21 gene was performed by using CAI, CHIPS and CUSP program of EMBOSS. Our study showed that codon usage bias of DEV UL21 had strong bias towards the A-ended or T-ended codons, and GC3s contents of the codon usage bias in DEV UL21 gene were significantly varied compared with those of other 27 reference herpesviruses. The CAI, ENC value of DEV CHv strain UL21 gene is 0.615 and 55.167, respectively, indicating that the codon usage bias of this gene is weak and lowly expressed. The plot of ENC versus GC3S content revealed that DEV UL21 gene is subject to GC compositional constraints. The phylogentic analysis about amino acids codon usage bias of DEV UL21 and the27 reference herpesviruses showed that DEV was evolutionarily closer to herpesviruses Mardivirus. In addition, the codon usage bias of DEV UL21 gene was compared with those of E. coli, yeast and humans. There are 42, 45, 39 same codons usage bias between the DEV UL21 to E.coli, Yeast, H.sapiens, respectively, indicaiting that UL21 gene of DEV may be more efficiently expressed in the yeast system.

A novel, generic and effective method for the rapid purification of G protein-coupled receptors

G protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors and are of major therapeutic importance. Structure determination of G protein-coupled receptors and other applications require milligram quantities of purified receptor proteins on a regular basis. Recombinant GPCRs fused to a heterologous biotinylation domain were produced in the yeast Pichia pastoris. We describe an efficient method for their rapid purification that relies on the capture of these receptors with streptavidin immobilized on agarose beads, and their subsequent release by enzymatic digestion with TEV protease. This method has been applied to several GPCRs belonging to the class A rhodopsin subfamily, leading to high yields of purified proteins; it represents a method of choice for biochemical and biophysical studies when large quantities of purified GPCRs are needed.

Monitoring the human beta1, beta2, beta3 adrenergic receptors expression and purification in Pichia pastoris using the fluorescence properties of the enhanced green fluorescent protein

The three beta adrenergic receptor subtypes, beta1-, beta2- and beta3-, were expressed in the methylotrophic yeast Pichia pastoris. These receptors were N-terminally fused to the enhanced green fluorescent protein (EGFP) and the fluorescent properties of EGFP were used: (1) to select the recombinant strains, (2) to monitor the expression of the fluorescent receptors, and (3) to monitor the purification of the receptors by immobilized metal affinity chromatography. We demonstrate here that Pichia pastoris can be an alternative host to express and purify milligram amounts of human beta adrenergic receptors.