Abstract
Preclinical evaluation of Retrocyclins (RC-100, RC-101) and Protegrin-1 (PG-1) antimicrobial peptides (AMPs) is important because of their therapeutic potential against bacterial, fungal and viral infections. Human mast cells (HMCs) play important roles in host defense and wound healing but the abilities of retrocyclins and protegrin-1 to harness these functions have not been investigated. Here, we report that chemically synthesized RC-100 and PG-1 caused calcium mobilization and degranulation in HMCs but these responses were not blocked by an inhibitor of formyl peptide receptor-like 1 (FPRL1), a known receptor for AMPs. However, RC-100 and PG-1 induced degranulation in rat basophilic leukemia (RBL-2H3) cells stably expressing Mas related G protein coupled receptor X2 (MrgX2). Chemical synthesis of these AMPs is prohibitively expensive and post-synthesis modifications (cyclization, disulfide bonds, folding) are inadequate for optimal antimicrobial activity. Indeed, we found that synthetic RC-100, which caused mast cell degranulation via MrgX2, did not display any antimicrobial activity. Green-fluorescent protein (GFP)-tagged RC-101 (analog of RC-100) and GFP-tagged PG-1 purified from transgenic plant chloroplasts killed bacteria and induced mast cell degranulation. Furthermore, GFP-PG1 bound specifically to RBL-2H3 cells expressing MrgX2. These findings suggest that retrocyclins and protegrins activate HMCs independently of FPRL1 but via MrgX2. Harnessing this novel feature of AMPs to activate mast cell's host defense/wound healing properties in addition to their antimicrobial activities expands their clinical potential. Low cost production of AMPs in plants should facilitate their advancement to the clinic overcoming major hurdles in current production systems.
Highlights
Antibiotics have been used for treatment of microbial infections since the early 1900s but emergence of multidrug resistant strains of microbes poses a tremendous public health concern globally [1]
We have recently shown that the antimicrobial peptides (AMPs) such as human β-defensins and the cathelicidin LL-37 activate human mast cells via Mas related G protein coupled receptor X2 (MrgX2) to induce G protein-mediated Ca2+ mobilization and robust mast cell degranulation [6, 7]
We used laboratory of allergic diseases 2 (LAD2) cells to determine the effects of PG-1 and RC-100 on mast cell signaling and degranulation
Summary
Antibiotics have been used for treatment of microbial infections since the early 1900s but emergence of multidrug resistant strains of microbes poses a tremendous public health concern globally [1]. Cationic antimicrobial peptides (AMP), known as host defense peptides (HDPs) such as the cathelicidin LL-37 and human β-defensins (hBDs) have the potential to be utilized as antimicrobial agents [2-4]. In addition to their direct antimicrobial activity, LL37 and hBDs display immunomodulatory properties which include the recruitment and activation of immune cells such as mast cells, neutrophils, monocytes and T cells [59]. These AMPs modulate angiogenesis and promote wound healing [10-12]. Great strides have www.impactjournals.com/oncotarget been made in recent years in identifying and optimizing AMPs for lower toxicity with greater stability/activity, which can harness the immune system for therapeutic benefits [15, 16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
