The methylation of amide nitrogen atoms can improve the stability, oral availability, and cell permeability of peptide therapeutics. Chemical N -methylation of peptides is challenging. Omphalotin A is a ribosomally synthesized, macrocylic dodecapeptide with nine backbone N -methylations. The fungal natural product is derived from the precursor protein, OphMA, harboring both the core peptide and a SAM-dependent peptide α- N -methyltransferase domain. OphMA forms a homodimer and its α- N -methyltransferase domain installs the methyl groups in trans on the hydrophobic core dodecapeptide and some additional C-terminal residues of the protomers. These post-translational backbone N -methylations occur in a processive manner from the N- to the C-terminus of the peptide substrate. We demonstrate that OphMA can methylate polar, aromatic, and charged residues when these are introduced into the core peptide. Some of these amino acids alter the efficiency and pattern of methylation. Proline, depending on its sequence context, can act as a tunable stop signal. Crystal structures of OphMA variants have allowed rationalization of these observations. Our results hint at the potential to control this fungal α- N -methyltransferase for biotechnological applications.

Body temperature is maintained at around 37 °C in humans, but may rise to 40 °C or more during high‐grade fever, which occurs in most adults who are seriously ill. However, endogenous temperature sensors, such as ion channels and heat‐shock promoters, are fully activated only at noxious temperatures above this range, making them unsuitable for medical applications. Here, a genetically encoded protein thermometer (human enhanced gene activation thermometer; HEAT) is designed that can trigger transgene expression in the range of 37–40 °C by linking a mutant coiled‐coil temperature‐responsive protein sensor to a synthetic transcription factor. To validate the construct, a HEAT‐transgenic monoclonal human cell line, FeverSense, is generated and it is confirmed that it works as a fever sensor that can temperature‐ and exposure‐time‐dependently trigger reporter gene expression in vitro and in vivo. For translational proof of concept, microencapsulated designer cells stably expressing a HEAT‐controlled insulin production cassette in a mouse model of type‐1 diabetes are subcutaneously implanted and topical heating patches are used to apply heat corresponding to a warm sensation in humans. Insulin release is induced, restoring normoglycemia. Thus, HEAT appears to be suitable for practical electrothermal control of cell‐based therapy, and may also have potential for next‐generation treatment of fever‐associated medical conditions.

Precise control of the delivery of therapeutic proteins is critical for gene- and cell-based therapies, and expression should only be switched on in the presence of a specific trigger signal of appropriate magnitude. Focusing on the advantages of delivering the trigger by inhalation, we have developed a mammalian synthetic gene switch that enables regulation of transgene expression by exposure to the semi-volatile small molecule acetoin, a widely used, FDA-approved food flavor additive. The gene switch capitalizes on the bacterial regulatory protein AcoR fused to a mammalian transactivation domain, which binds to promoter regions with specific DNA sequences in the presence of acetoin and dose-dependently activates expression of downstream transgenes. Wild-type mice implanted with alginate-encapsulated cells transgenic for the acetoin gene switch showed a dose-dependent increase in blood levels of reporter protein in response to either administration of acetoin solution via oral gavage or longer exposure to acetoin aerosol generated by a commercial portable inhaler. Intake of typical acetoin-containing foods, such as butter, lychees and cheese, did not activate transgene expression. As a proof of concept, we show that blood glucose levels were normalized by acetoin aerosol inhalation in type-I diabetic mice implanted with acetoin-responsive insulin-producing cells. Delivery of trigger molecules using portable inhalers may facilitate regular administration of therapeutic proteins via next-generation cell-based therapies to treat chronic diseases for which frequent dosing is required.

Rapid insulin release plays an essential role in maintaining blood‐glucose homeostasis in mammalians. Patients diagnosed with type‐I diabetes mellitus experience chronic and remarkably high blood‐sugar levels, and require lifelong insulin injection therapy, so there is a need for more convenient and less invasive insulin delivery systems to increase patients’ compliance and also to enhance their quality of life. Here, an endoplasmic‐reticulum‐localized split sec‐tobacco etch virus protease (TEVp)‐based rapamycin‐actuated protein‐induction device (RAPID) is engineered, which is composed of the rapamycin‐inducible dimerization domains FK506 binding protein (FKBP) and FKBP‐rapamycin binding protein fused with modified split sec‐TEVp components. Insulin accumulation inside the endoplasmic reticulum (ER) is achieved through tagging its C‐terminus with KDEL, an ER‐retention signal, spaced by a TEVp cleavage site. In the presence of rapamycin, the split sec‐TEVp‐based RAPID components dimerize, regain their proteolytic activity, and remove the KDEL retention signal from insulin. This leads to rapid secretion of accumulated insulin from cells within few minutes. Using liver hydrodynamic transfection methodology, it is shown that RAPID quickly restores glucose homeostasis in type‐1‐diabetic (T1DM) mice treated with an oral dose of clinically licensed rapamycin. This rapid‐release technology may become the foundation for other cell‐based therapies requiring instantaneous biopharmaceutical availability.