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Exendin-4 with a N-terminal secretion tag and a C-terminal cell penetrating peptide

Exendin-4 is a GLP-1 analogon out of Heloderma suspectum and functions as an Incretin mimetic. It is fused with a N-termianl secretion tag to allow it to be secreted by a bacterium. Additionally, a C-terminal cell penetrating peptide was added to ensure that Exendin-4 can pass through the intestinal cells and enter the bloodstream in order to reach the pancreas where it enhances the Insulin secretion. The CPP in this composite part is Penetratin.

Background

In the iGEM Team Tübingen 2019 project, Exendin-4 was used as a therapeutic for the treatment of Type 2 Diabetes mellitus with probiotics. Exendin-4 is, in contrast to its human analogue more stable and not as easily degraded by DPP-IV peptidase. Thus, a suitable candidate for a therapeutic. This part is a composite, which allows for the secretion of Exendin-4 and a cell penetrating peptide -Penetratin- for the delivery of Exendin-4 into the circulatory system.

Usage and Biology

Exendin-4 is used as a treatment for Type 2 Diabetes mellitus. Its human analogue gLP-1 originates from the prepeptide proglucagon, which is cleaved into, among others, GLP-1 (1-37) by prohormone convertase 1 (PC1) (Lim et al. 2006). The inactive GLP-1 (1-37) is then processed into its active form GLP-1 (7-37) by an endopeptidase. This active form is secreted and diffuses across the basal lamina and enters the lamina propria, where it is taken up into the capillaries, reaching the circulatory system (Lim et al. 2006).The glucagon like peptide binds to a GPCR on the pancreatic beta cells, which will cause an intracellular cascade activating an Adenylate Cyclase. If ATP is available within the cell, which means if the cell has already taken up sugar and run through glycolysis, cAMP will be produced (Jens Juul Holst, 2007). Overall, this will result in prolonged depolarization and calcium ion influx and consequently more secretion of insulin from the beta cells (Jens Juul Holst, 2007). This increase in insulin secretion can overcome the relative lack of insulin in the periphery of Type 2 Diabetes mellitus(Jens Juul Holst, 2007).

Exendin-4 and GLP-1 do not only have a direct effect on the pancreas, but also decrease gastrointestinal motility and secretion, hunger and the emptying of the stomach, thus helping in weight reduction (Jens Juul Holst, 2007). Additionally, they are considered to be cardioprotective(Jens Juul Holst, 2007). This is very important for the therapy, since many cases of Type 2 DM are caused by an unhealthy lifestyle and obesity(Jens Juul Holst, 2007).

Sequence and Features

References

1. Holst, Jens Juul. The physiology of glucagon-like peptide 1. Physiological reviews 87.4 (2007): 1409-1439.
2. KR 1020120130606-A/1: Secretion signal peptide linked Exendin-4 gene transduced pancreatic islet cluster for treatment of type I diabetes
3. Lim, Gareth E., Brubaker, Patricia L. Glucagon-Like Peptide 1 Secretion by the L-Cell. (2006). 10.2337/db06-S020. Diabetes. p. S70-S77
4. Copley, Kathrin, et al. "Investigation of exenatide elimination and its in vivo and in vitro degradation." Current drug metabolism 7.4 (2006): 367-374.