Expression and purification of natural N-terminal recombinant bovine pancreatic trypsin inhibitor from Pichia pastoris

The α-mating factor secretion signals and endogenous signal peptides for recombinant protein secretion in Komagataella phaffii

BACKGROUND

The budding yeast Komagataella phaffii (Pichia pastoris) is widely employed to secrete proteins of academic and industrial interest. For secretory proteins, signal peptides are the sorting signal to direct proteins from cytosol to extracellular matrix, and their secretion efficiency directly impacts the yields of the targeted proteins in fermentation broth. Although the α-mating factor (MF) secretion signal from S. cerevisiae, the most common and widely used signal sequence for protein secretion, works in most cases, limitation exists as some proteins cannot be secreted efficiently. As the optimal choice of secretion signals is often protein specific, more secretion signals need to be developed to augment protein expression levels in K. phaffii.

RESULTS

In this study, the secretion efficiency of 40 α-MF secretion signals from various yeast species and 32 endogenous signal peptides from K. phaffii were investigated using enhanced green fluorescent protein (EGFP) as the model protein. All of the evaluated α-MF secretion signals successfully directed EGFP secretion except for the secretion signals of the yeast D. hansenii CBS767 and H. opuntiae. The secretion efficiency of α-MF secretion signal from Wickerhamomyces ciferrii was higher than that from S. cerevisiae. 24 out of 32 endogenous signal peptides successfully mediated EGFP secretion. The signal peptides of chr3_1145 and FragB_0048 had similar efficiency to S. cerevisiae α-MF secretion signal for EGFP secretion and expression.

CONCLUSIONS

The screened α-MF secretion signals and endogenous signal peptides in this study confer an abundance of signal peptide selection for efficient secretion and expression of heterologous proteins in K. phaffii.

Improved Production of Xylanase in Pichia pastoris and Its Application in Xylose Production From Xylan

Xylanases with high specific activity has been focused with great interest as a useful enzyme in biomass utilization. The production of recombinant GH11 xylanase (MYCTH_56237) from Myceliophthora thermophila has been improved through N-terminal signal peptide engineering in P. pastoris. The production of newly recombinant xylanase (termed Mtxyn11C) was improved from 442.53 to 490.7 U/mL, through a replacement of α-factor signal peptide with the native xylanase signal peptide segment (MVSVKAVLLLGAAGTTLA) in P. pastoris. Scaling up of Mtxyn11C production in a 7.5 L fermentor was improved to the maximal production rate of 2503 U/mL. In this study, the degradation efficiency of Mtxyn11C was further examined. Analysis of the hydrolytic mode of action towards the birchwood xylan (BWX) revealed that Mtxyn11C was clearly more effective than commercial xylanase and degrades xylan into xylooligosaccharides (xylobiose, xylotriose, xylotetraose). More importantly, Mtxyn11C in combination with a single multifunctional xylanolytic enzyme, improved the hydrolysis of BWX into single xylose by 40%. Altogether, this study provided strategies for improved production of xylanase together with rapid conversion of xylose from BWX, which provides sustainable, cost-effective and environmental friendly approaches to produce xylose/XOSs for biomass energy or biofuels production.

A systematic analysis of the expression of the anti-HIV VRC01 antibody in Pichia pastoris through signal peptide optimization

Pichia pastoris (Komagataella phaffi) has been used for recombinant protein production for over 30 years with over 5000 proteins reported to date. However, yields of antibody are generally low. We have evaluated the effect of secretion signal peptides on the production of a broadly neutralizing antibody (VRC01) to increase yield. Eleven different signal peptides, including the murine IgG1 signal peptide, were combinatorially evaluated for their effect on antibody titer. Strains using different combinations of signal peptides were identified that secreted approximately 2-7 fold higher levels of VRC01 than the previous best secretor, with the highest yield of 6.50 mg L-1 in shake flask expression. Interestingly it was determined that the highest yields were achieved when the murine IgG1 signal peptide was fused to the light chain, with several different signal peptides leading to high yield when fused to the heavy chain. Finally, we have evaluated the effect of using a 2A signal peptide to create a bicistronic vector in the attempt to reduce burden and increase transformation efficiency, but found it to give reduced yields compared to using two independent vectors.

Recombinant bovine pancreatic trypsin inhibitor protects the liver from carbon tetrachloride-induced chronic injury in rats

CONTEXT

Bovine pancreatic trypsin inhibitor (BPTI) has been reported to relieve liver ischemia-reperfusion-induced injury in rats.

OBJECTIVE

This study was designed to determine whether the recombinant BPTI (rBPTI) can prevent the chronic liver injury induced by CCl4 in rats.

MATERIALS AND METHODS

Fifty male Wistar rats were divided into five groups. Rats were treated with 40% CCl4 at a dose of 2 ml/kg body weight twice a week subcutaneously for 12 weeks. In the 8th week, they were administered intraperitoneally with rBPTI (80 MU/kg), BPTI (80 MU/kg) or hepatocyte growth-promoting factor (pHGF; 100 mg/kg) daily for the next 4 weeks.

RESULTS

rBPTI significantly prevented the disruption of liver function of alanine aminotransferase (ALT; 172.7 ± 18.16 versus 141.2 ± 15.28, p=0.003), aspartate aminotransferase (AST; 225.10 ± 36.54 versus 170.06 ± 27.14, p=0.007) and hydroxyproline (Hyp; 1.14 ± 0.27 versus 0.62 ± 0.17, p=0.001). rBPTI significantly decreased the level of thiobarbituric acid reactive substances (TBARS; 1.15 ± 0.16 versus 0.87 ± 0.15, p=0.003) and increased the activities of superoxide dismutase (SOD; 6.07 ± 0.95 versus 7.75 ± 1.12, p=0.007). rBPTI reduced the production of cytokines of IL-1β and TGF-β. The hepatocyte necrosis, fibrosis, fatty degeneration and inflammatory cell infiltration were ameliorated by rBPTI administration.

CONCLUSION

This study demonstrated that rBPTI exerted a hepatoprotective effect on chronic liver fibrosis induced by CCl4, which suggests that rBPTI may have the potential application for chronic liver injury induced by drugs metabolism and toxic substances.

Improved secretion of Candida antarctica lipase B with its native signal peptide in Pichia pastoris

Secretion efficiency of the 85-amino acid Sacchromyces cerevisiae alpha signal peptide and the 25-amino acid Candida antarctica lipase B signal (nsB) peptide were compared. Three reporter proteins used for the study are C. antarctica lipase A (CalA), lipase B (CalB) and hGMCSF. The copy number of recombinant α-CalB and nsB-CalB clones was determined by qPCR and clones with equivalent gene copies were used for comparative analysis. About threefold increased CalB production corresponding to an activity of 480 U ml(-1) was obtained with its native signal peptide, whereas with the alpha signal peptide the maximum activity was 160 U ml(-1). Also, CalB was secreted as a mature protein with native N-terminus when fused to its own signal peptide, while unprocessed CalB with N-terminal extension was detected with the alpha signal peptide. Real time PCR analysis of CalB strains indicated that the difference in protein expression was not at the transcriptional level. The nsB signal sequence was also effective in secreting CalA enzyme and its secretion efficiency was on par with the alpha signal sequence. Further, hGMCSF fused inframe with the nsB signal peptide was also efficiently secreted into the medium. These results indicate that the nsB signal peptide can be a better alternative to alpha signal peptide for heterologous protein expression in Pichia pastoris.

Recombinant bovine pancreatic trypsin inhibitor protects the liver from carbon tetrachloride-induced acute injury in mice

OBJECTIVES

Toxicity caused by pharmacological and chemical substances, including carbon tetrachloride (CCl(4)), is a major pathological factor for liver injury. Therefore, strategies to prevent toxicity are needed for maintaining a healthy liver. This study was designed to determine whether recombinant bovine pancreatic trypsin inhibitor (rBPTI), a non-specific serine protease inhibitor, prevents CCl(4)-induced liver injury in mice.

METHODS

Mice were treated with CCl(4) in the presence or absence of co-treatment with rBPTI. Liver sections were prepared for histopathological assessment. Liver function was evaluated by detecting serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and liver index. Liver oxidative stress and inflammation were examined by detecting the liver malondialdehyde level and glutathione and superoxide dismutase activity, and serum tumour necrosis factor-alpha level, respectively.

KEY FINDINGS

CCl(4) induced hepatocyte necrosis, inflammatory cell infiltration and fatty degeneration, which were ameliorated by co-treatment with rBPTI in a concentration-dependent manner. Furthermore, rBPTI prevented CCl(4)-induced disruption of liver function. Importantly, rBPTI reduced CCl(4)-induced liver oxidative stress response and pro-inflammatory cytokine production.

CONCLUSIONS

These results indicated that rBPTI exerted a protective effect on CCl(4)-induced liver injury in mice. Thus, rBPTI may have potential application for prevention of liver injury induced by metabolism of drugs and toxic substances.