Background Low-temperature expression of recombinant proteins may be advantageous to support their proper folding and preserve bioactivity. The generation of expression vectors regulated under cold conditions can improve the expression of some target proteins that are difficult to express in different expression systems. Main body of the abstract The cspA encodes the major cold-shock protein from Escherichia coli (CspA). The promoter of cspA has been widely used to develop cold shock-inducible expression platforms in E. coli. Moreover, it is often necessary to employ expression systems other than bacteria, particularly when recombinant proteins require complex post-translational modifications. Currently, there are no commercial platforms available for expressing target genes by cold shock in eukaryotic cells. Consequently, genetic elements that respond to cold shock offer the possibility of developing novel cold-inducible expression platforms, particularly suitable for yeasts, and mammalian cells. Conclusions This review covers the importance of the cellular response to low temperatures and the prospective use of cold-sensitive promoters to direct the expression of recombinant proteins. This concept may contribute to renewing interest in applying white technologies to produce recombinant proteins that are difficult to express. Graphical Abstract

The production of recombinant biopharmaceutical proteins is a multi-billion dollar market. Protein recovery represents a major part of the production costs. Pichia pastoris is one of the microbial systems most used for the production of heterologous proteins. The use of a cold-induced promoter to express lytic enzymes in the yeast after the growth stage could reduce protein recovery costs. This study shows that a cold-shock can be applied to induce lysis of the yeast cells. A strain of P. pastoris was constructed in which the endogenous eng gene encoding a putative endo-β-1,3-glucanase was overexpressed using the cold-shock induced promoter of the cctα gene from Saccharomyces cerevisiae. In the transgenic P. pastoris, the expression of eng increased 3.6-fold after chilling the cells from 30 to 4 °C (cold-shock stage) followed by incubation for 6 h (eng expression stage). The culture was heated to 30 °C for 6 h (ENG synthesis stage) and kept at 37 °C for 24 h (lysis stage). After this procedure the cell morphology changed, spheroplasts were obtained and cellular lysis was observed. Thus, a clone of P. pastoris was obtained, which undergoes autolysis after a cold-shock.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0397-y) contains supplementary material, which is available to authorized users.

Extracellular vesicles (EVs) are evaginations of the cytoplasmic membrane, containing nucleic acids, proteins, lipids, enzymes, and toxins. EVs participate in various bacterial physiological processes. Staphylococcus epidermidis interacts and communicates with the host skin. S. epidermidis’ EVs may have an essential role in this communication mechanism, modulating the immunological environment. This work aimed to evaluate if S. epidermidis’ EVs can modulate cytokine production by keratinocytes in vitro and in vivo using the imiquimod-induced psoriasis murine model. S. epidermidis’ EVs were obtained from a commensal strain (ATC12228EVs) and a clinical isolated strain (983EVs). EVs from both origins induced IL-6 expression in HaCaT keratinocyte cultures; nevertheless, 983EVs promoted a higher expression of the pro-inflammatory cytokines VEGF-A, LL37, IL-8, and IL-17F than ATCC12228EVs. Moreover, in vivo imiquimod-induced psoriatic skin treated with ATCC12228EVs reduced the characteristic psoriatic skin features, such as acanthosis and cellular infiltrate, as well as VEGF-A, IL-6, KC, IL-23, IL-17F, IL-36γ, and IL-36R expression in a more efficient manner than 983EVs; however, in contrast, Foxp3 expression did not significantly change, and IL-36 receptor antagonist (IL-36Ra) was found to be increased. Our findings showed a distinctive immunological profile induction that is dependent on the clinical or commensal EV origin in a mice model of skin-like psoriasis. Characteristically, proteomics analysis showed differences in the EVs protein content, dependent on origin of the isolated EVs. Specifically, in ATCC12228EVs, we found the proteins glutamate dehydrogenase, ornithine carbamoyltransferase, arginine deiminase, carbamate kinase, catalase, superoxide dismutase, phenol-soluble β1/β2 modulin, and polyglycerol phosphate α-glucosyltransferase, which could be involved in the reduction of lesions in the murine imiquimod-induced psoriasis skin. Our results show that the commensal ATCC12228EVs have a greater protective/attenuating effect on the murine imiquimod-induced psoriasis by inducing IL-36Ra expression in comparison with EVs from a clinical isolate of S. epidermidis.

ATP citrate lyase (ACL), is a key cytosolic source of acetyl-CoA for fatty acid and sterol biosynthesis and appear to be involved in carotenoid biosynthesis in yeasts. Three homologous DNA sequences encoding ACLs in Phaffia rhodozyma were isolated i.e two genes and one cDNA. The two genes were multi-intronic, with 3450-bp-coding sequences and both genes, as the cDNA, encoded identical 120.1-kDa polypeptides. Full-length amino acid sequences of these ACLs showed the two multidomains, PLN02235 and PLN02522, which are necessary for activity. The ACLs showed 82-87% similarity to putative ACLs from other basidiomycetes and 71% similarity to human ACL. The acl cDNA was used to express the heterologous ACL 6XHis-tagged which was identified using MALDI-TOF-MS. The sequenced peptides with 42.2% coverage showed 100% identity to the amino acid sequence generated in silico. The recombinant ACL purified to homogeneity showed an activity of 2 U. This is the first study to characterize a recombinant ACL from a carotenogenic yeast. The present study provides a key foundation for future studies to assess (a) the possible occurrence of alternative splicing, (b) identify the promoter(s) sequence(s) and (c) the involvement of ACL in the differential regulation of fatty acid and carotenoid biosynthesis in yeasts.