Scale-up production of and dietary supplementation with the recombinant antimicrobial peptide tilapia piscidin 4 to improve growth performance in Gallus gallus domesticus

Growth-promoting effect of antimicrobial peptide Scy-hepc on mariculture large yellow croaker Larimichthys crocea and the underlying mechanism

With the antibiotics prohibition in feedstuffs worldwide, antimicrobial peptides (AMPs) are considered a more promising substitute for antibiotics to be used as feed additives, and positive results have been reported in livestock feeding studies. However, whether dietary supplementation of AMPs could promote the growth of mariculture animals such as fish and the underlying mechanism has not been elucidated yet. In the study, a recombinant AMP product of Scy-hepc was used as a dietary supplement (10 mg/kg) to feed mariculture juvenile large yellow croaker (Larimichthys crocea) with an average initial body weight (BW) of 52.9 g for 150 days. During the feeding trial, the fish fed with Scy-hepc showed a significant growth-promoting performance. Especially at 60 days after feeding, fish fed with Scy-hepc weighed approximately 23% more than the control group. It was further confirmed that the growth-related signaling pathways such as the GH-Jak2-STAT5-IGF1 growth axis, the PI3K-Akt and Erk/MAPK pathways were all activated in the liver after Scy-hepc feeding. Furthermore, a second repeated feeding trial was scheduled for 30 days using much smaller juvenile L. crocea with an average initial BW of 6.3 g, and similar positive results were observed. Further investigation revealed that the downstream effectors of the PI3K-Akt pathway, such as p70S6K and 4EBP1, were significantly phosphorylated, suggesting that Scy-hepc feeding might promote translation initiation and protein synthesis processes in the liver. Taken together, as an effector of innate immunity, AMP Scy-hepc played a role in promoting the growth of L. crocea and the underlying mechanism was associated with the activation of the GH-Jak2-STAT5-IGF1 axis, as well as the PI3K-Akt and Erk/MAPK signaling pathways.

The future of recombinant host defense peptides

The antimicrobial resistance crisis calls for the discovery and production of new antimicrobials. Host defense peptides (HDPs) are small proteins with potent antibacterial and immunomodulatory activities that are attractive for translational applications, with several already under clinical trials. Traditionally, antimicrobial peptides have been produced by chemical synthesis, which is expensive and requires the use of toxic reagents, hindering the large-scale development of HDPs. Alternatively, HDPs can be produced recombinantly to overcome these limitations. Their antimicrobial nature, however, can make them toxic to the hosts of recombinant production. In this review we explore the different strategies that are used to fine-tune their activities, bioengineer them, and optimize the recombinant production of HDPs in various cell factories.

Studying Peptide-Metal Ion Complex Structures by Solution-State NMR

Metal chelation can provide structural stability and form reactive centers in metalloproteins. Approximately one third of known protein structures are metalloproteins, and metal binding, or the lack thereof, is often implicated in disease, making it necessary to be able to study these systems in detail. Peptide-metal complexes are both present in nature and can provide a means to focus on the binding region of a protein and control experimental variables to a high degree. Structural studies of peptide complexes with metal ions by nuclear magnetic resonance (NMR) were surveyed for all the essential metal complexes and many non-essential metal complexes. The various methods used to study each metal ion are presented together with examples of recent research. Many of these metal systems have been individually reviewed and this current overview of NMR studies of metallopeptide complexes aims to provide a basis for inspiration from structural studies and methodology applied in the field.

Strategies for improving antimicrobial peptide production

Antimicrobial peptides (AMPs) found in a wide range of animal, insect, and plant species are host defense peptides forming an integral part of their innate immunity. Although the exact mode of action of some AMPs is yet to be deciphered, many exhibit membrane lytic activity or interact with intracellular targets. The ever-growing threat of antibiotic resistance has brought attention to research on AMPs to enhance their clinical use as a therapeutic alternative. AMPs have several advantages over antibiotics such as broad range of antimicrobial activities including anti-fungal, anti-viral and anti-bacterial, and have not reported to contribute to resistance development. Despite the numerous studies to develop efficient production methods for AMPs, limitations including low yield, degradation, and loss of activity persists in many recombinant approaches. In this review, we outline available approaches for AMP production and various expression systems used to achieve higher yield and quality. In addition, recent advances in recombinant strategies, suitable fusion protein partners, and other molecular engineering strategies for improved AMP production are surveyed.