In Silico Investigation of the Binding of MCoTI-II Plant Defense Knottin to the γ-NGF Serine Protease of the 7S Nerve Growth Factor Complex and Biological Activity of Its NGF Mimetic Properties

Abstract

Nerve growth factor (NGF) is an endogenously produced polypeptide that promotes the differentiation, survival, and repair of neurons in the central and peripheral nervous systems. While trophic proteins hold promise for the treatment of neuronal injury and disease, use of NGF is limited by its large molecular weight, lack of permeability through the blood–brain barrier, and peripheral side effects. Previously, we found that an extract of the Momordica cochinchinensis seed stimulated PC-12 neurite outgrowth. Bioactivity-guided fractioning of the seed extract suggested that the NGF mimetic agent was one of few defined proteins from this plant: one group being the defense Knottins and the other group of the lowest mass is the potent trypsin inhibitor MCoTI-II. Here, the NGF mimetic potential of this latter protein was investigated using two concurrent but different approaches. A biological study used recombinant purified MCoTI-II, which when tested in rat PC-12 cells grown on collagen, failed to initiate outgrowth relative to the positive control 7S NGF. In a separate computational study, the possibility was investigated such that MCoTI-II could exert an effect through binding to the serine protease γ-NGF subunit of the 7S NGF complex, analogous to its binding to its native receptor trypsin. Molecular dynamics simulations showed that MCoTI-II can bind stably to γ-NGF for >350 ns. Modeling indicated that this interaction could sterically inhibit 7S NGF complex formation, potentially altering the equilibrium between inactive complexed and free active NFG protein. In conclusion, the biological study now excludes the MCoTI-II protein as the NGF mimetic factor in the Momordica extract, an important and required step to identify the active component in this seed. On the other hand, the theoretical study has revealed a novel observation that may be of use in the development of strategies to affect NGF activity.

Phytochemical Targeting of Nerve Growth Factor by Thymoquinone and Cuscutin: A Molecular Dynamics Simulation Study

“…NGF is a neuroprotein, and targeting it is a complex process. NGF inhibition provides varied benefits in OSCC by reducing pain and inflammation [ 17 , 18 ], reducing tumorigenesis, and aiding in weight loss management [ 9 ]. This study is based on the computer-based drug design approach targeting NGF using phytochemicals.…”

“…This study is based on the computer-based drug design approach targeting NGF using phytochemicals. NGF is a protein stimulating neurite growth [ 17 ]. NGF is a neurotrophin produced by immune cells, endothelial cells, and nerve tissue.…”

“…These neurotrophin effects are mediated when binding to the cell-surface receptors like tropomyosin-related kinase receptor/tropomyosin receptor kinase A (TrkA) and p75 neurotrophin receptor (NGFR/p75NTR), of which TrkA is mainly expressed on the cancer cell surface [ 17 ]. The phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) are the two main signaling pathways that get altered when NGF binds to the TrkA receptor, thus affecting cell growth, differentiation, and nociceptive effects [ 18 ].…”

“…NGF secretion is induced by excessive reactive oxygen species (ROS) production by cancer cells, which is associated with excessive pain generation. Also, NGF plays a significant role in cancer stem cell production [ 17 ]. Doan et al [ 8 ] stated that the blockade of TrkA and NGF receptors inhibited pain, proliferation, and invasion of OSCC in preclinical and in vitro models.…”

Virtual Issue on Docking

“…24 The formation of β-sheetrich aggregates of poly(L-lysine) and poly(L-glutamic acid) were modeled using a peptide fragment dock approach that resulted in antiparallel β-sheets. 25 Docking methods can also be applied to larger protein/protein complexes, such as the dimerization of cytochrome P450 with organophosphorus hydrolase, 26 MCoTI-II (trypsin inhibitor) to γ-nerve growth factor, 27 and nanobody-protein structural prediction. 28 Published: June 3, 2021 Docking methods have also been applied to proteins at hard material interfaces.…”