Overexpressed Arabidopsis Annexin4 accumulates in inclusion body-like structures

Lab-scale Preparation of Recombinant Human Insulin-like Growth Factor-1 in Escherichia coli and its Potential Safety on Normal Human Lung Cell Line

BACKGROUND

Insulin-like growth factor-1 (IGF-1) is structurally similar to insulin and acts as an endocrine hormone secreted by the liver.

OBJECTIVE

Production of recombinant human IGF-1 (rhIGF-1) in Escherichia coli (E.coli) and evaluation of its proliferation stimulatory activity.

METHODS

hIGF-1 gene cloned into pBSK (+) simple vector was transformed into TOP 10 chemically competent cells of E. coli. Polymerase chain reaction (PCR) was achieved using specific hIGF-1 gene primers to confirm the successful transformation. To express the rhIGF-1 in E. coli (Rosetta (DE3) pLysS); the hIGF-1 gene was cloned into the pET-15b expression vector and then the recombinant pET-15b/IGF-1 vector was transformed into a chemically prepared competent expression bacterial cells; Rosetta (DE3) pLysS. The rhIGF-1 was expressed as insoluble aggregates called inclusion bodies (IBs) using a 2 mM Isopropyl β-D-1-thiogalactopyranoside (IPTG) inducer. IBs were solubilized in a denatured form using 6 M guanidinium hydrochloride (GdmCl), followed by in vitro protein refolding using the rapid dilution method. The refolded hIGF-1 was purified using the HiTrap- ANX anion exchange column. Western blot and ELISA using rabbit polyvalent anti-hIGF- 1 were performed to confirm the protein antigenic identity. Cell proliferation activity of rhIGF-1 was testified on normal human lung cell line (WI-38).

RESULTS

rhIGF-1 was purified from the HiTrap-ANX column at a concentration of 300 μg/ml. Western blot showed a single 7.6 kDa band obtained in the induced Rosetta (DE3) pLYsS. ELISA confirmed the molecular identity of the rhIGF-1 epitope, the concentration of purified rhIGF-1 obtained from the ELISA standard curve using rhIGF-1 reference protein as a standard was 300 μg/ml, and activity on WI-38 cells was 2604.17I U/mg.

CONCLUSION

Biologically active native rhIGF-1 protein was successfully expressed. Patents related to the preparation of IGF-1 were mentioned along the text.

Functional protein aggregates: just the tip of the iceberg

An increasing number of both prokaryotic and eukaryotic cell types are being adapted as platforms for recombinant protein production. The overproduction of proteins in such expression systems leads to the formation of insoluble protein-based aggregates. Although these protein clusters have been poorly studied in most of the eukaryotic systems, aggregates formed in E. coli, named inclusion bodies (IBs), have been deeply characterized in the last decades. Contrary to the general belief, an important fraction of the protein embedded in IB is functional, showing promise in biocatalysis, regenerative medicine and cell therapy. Thus, the exploration of all these functional protein clusters would largely expand their potential in both pharma and biotech industry.