Importance of phosphoinositide binding by human β‐defensin 3 for Akt‐dependent cytokine induction

Abstract

Host defense peptides (HDPs) are well-characterized for their antimicrobial activities but also variously display potent immunomodulatory effects. Human β-defensin 3 (HBD-3) belongs to a well-known HDP family known as defensins and is able to induce leukocyte chemotactic recruitment, leukocyte activation/maturation, proinflammatory cytokine release, and co-stimulatory marker expression. HBD-3-stimulated cytokine induction is NF-κB-dependent and was initially suggested to act via G protein-coupled C-C chemokine receptor phospholipase C (PLC) and/or Toll-like receptor signaling. Subsequent pharmacological inhibition, however, revealed that NF-κB activation by HBD-3 is receptor-independent and instead involves the phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) pathway, the mechanism of which remains undetermined. Recently, we have shown that HBD-3 can enter mammalian cells and bind to inner membrane phosphoinositide 4,5-bisphosphate [PI(4,5)P], an important second lipid messenger of PLC and PI3K-Akt pathways. In this study, we report that the interaction of HBD-3 with PI(4,5)P is important for PI3K-Akt-NF-κΒ-mediated induction of tumor necrosis factor and interleukin-6. These data provide insights into the mechanism of immunomodulation by HBD-3, and more generally, highlight the complex multifaceted signaling roles of HDPs in innate defense. Furthermore, it is suggested that the proposed mode of action may be conserved in other HDPs.

The Designer Antimicrobial Peptide A-hBD-2 Facilitates Skin Wound Healing by Stimulating Keratinocyte Migration and Proliferation

“…PLC is a key signaling protein that plays a significant role in multiple physiological processes in cells. Previous studies have reported that AMPs can stimulate the release of cytokines via the activation of PLC signaling and have immunomodulatory effects [5,42]. The PLC-dependent pathway is involved in the A-hBD-2-induced production of cytokines and chemokines, as demonstrated by the inhibitory effects of U73122 against A-hBD-2 and confirmed by the decreased production of cytokines and chemokines.…”

Structural and functional characterization of the membrane‐permeabilizing activity of Nicotiana occidentalis defensin NoD173 and protein engineering to enhance oncolysis

“…Coincidentally, HBD‐3 can bind a range of phospholipids, including PIP2, which is important for its tumor cell permeabilization (30). Additionally, interaction of HBD‐3 with PIP2 was shown to be important for its immunomodulatory activity, particularly in PI3K‐Akt–NF‐κB–mediated cytokine induction of TNF and IL‐6 (54). Recently, HBD‐2 was also shown to bind several phospholipids, including PIP2 (28).…”

“…Defensins are a major family of HDPs and are ubiquitously found throughout the plant and animal kingdoms, where they play a vital role in innate defense, forming part of the chemical arsenal for the protection of their hosts (8, 9). In plants, these small (45–54 aa), basic, cysteine‐rich proteins are well documented for their antimicrobial activities against a range of fungi and bacteria (10–12). They are also able to inhibit proteinases, α‐amylases, and protein translation in eukaryotic and prokaryotic cell‐free systems (13–15), block ion channels (16, 17), or confer stress tolerances, such as to salinity and metal zinc (18–20).…”

Antiviral Effect of hBD-3 and LL-37 during Human Primary Keratinocyte Infection with West Nile Virus

“…Some pro-inflammatory properties of hBD-3 have been previously described. hBD-3 can induce inflammatory response by itself, through CCR6 binding or the G protein-coupled receptor (GPCR) and phospholipase C (PLC) signaling pathway, leading to the release of several cytokines such as IL-6, IL-10, IL-37, IFN-γ, CXL-10, CCL-2 and CCL-5 by human keratinocytes [ 55 , 56 ]. It can also modulate the response to TLR agonists.…”