Molecular Dynamics Simulations of a Stretch-Activated Channel Inhibitor GsMTx4 with Lipid Membranes: Two Binding Modes and Effects of Lipid Structure

Abstract

Our recent molecular dynamics simulation study of hanatoxin 1 (HaTx1), a gating modifier that binds to the voltage sensor of K(+) channels, has shown that HaTx1 has the ability to interact with carbonyl oxygen atoms of both leaflets of the lipid bilayer membrane and to be located at a deep position within the membrane. Here we performed a similar study of GsMTx4, a stretch-activated channels inhibitor, belonging to the same peptide family as HaTx1. Both toxins have an ellipsoidal shape, a belt of positively charged residues around the periphery, and a hydrophobic protrusion. Results show that, like HaTx1, GsMTx4 can interact with the membrane in two different ways. When all the positively charged residues interact with the outer leaflet lipid, GsMTx4 can assume a shallow binding mode. On the other hand, when the electrostatic interaction brings the positively charged groups of K-8 and K-28 into the vicinity of the carbonyl oxygen atoms of the inner leaflet lipids, the system exhibits a deep binding mode. This deep mode is accompanied by local membrane thinning. For both HaTx1 and GsMTx4, our mean force measurement analyses show that the deep binding mode is energetically favored over the shallow mode when a DPPC (dipalmitoyl-phosphatidylcholine) membrane is used at 310 K. In contrast, when a POPC (palmitooleoyl-phosphatidylcholine) membrane is used at 310 K, the two binding modes exhibited similar stability for both toxins. Similar analyses with DPPC membrane at 330 K led to an intermediary result between the above two results. Therefore, the structure of the lipid acyl chains appears to influence the location and the dynamics of the toxins within biological membranes. We also compared the behavior of an arginine and a lysine residue within the membrane. This is of interest because the arginine residue interaction with the lipid carbonyl oxygen atoms mediates the deep binding mode for HaTx1, whereas the lysine residue plays that role for GsMTx4. The arginine residue generally shows smoother dynamics near the lipid carbonyl oxygen atoms than the lysine residue. This difference between arginine and lysine may partly account for the functional diversity of the members of the toxin family.

The biophysics of piezo1 and piezo2 mechanosensitive channels

“…In fact, one of the main inhibitors of piezo1 and piezo2 channels is the Grammostola spatulata mechano-toxin GsTMx4 (Andolfo et al, 2013). The inhibition mechanism of this peptide is not directed against the channel, but it targets the cellular membrane, putatively penetrating the lipid bilayer and creating a transbilayer coupling (Nishizawa and Nishizawa, 2007). The abrupt change in membrane mobility induced by the presence of the link would probably affect the ability of the bilayer to transfer mechanical tension to membrane proteins and domains.…”

Effects of Lys to Glu mutations in GsMTx4 on membrane binding, peptide orientation, and self-association propensity, as analyzed by molecular dynamics simulations

“…GsMTx4 has been subjected to several computational analyses [9,10], but the interactions with membranes remain poorly understood. We expected that peptide binding would produce local deformation and local changes in membrane thickness and curvature [8,10], but these effects have not been systematically evaluated.…”

“…When the peptide is viewed from the side of the hydrophobic protrusion, six Lys residues and one Arg residue form a ring-like structure encircling the periphery (Figure 1). Our previous simulations suggested that GsMTx4 could interact with the lipid bilayer through a shallow (interfacial) binding mode and a deeper mode [9] wherein some Lys residues interacted with lipid head groups of the inner monolayer while the remaining Lys interacted with head groups of the outer monolayer. At low concentrations GsMTx4 inhibits bacterial channels MscS and MscL, but at higher concentrations there may be potentiation which might reflect a concentration-dependent transition from shallow to deep binding mode [11,12].…”

A Venom-derived Neurotoxin, CsTx-1, from the Spider Cupiennius salei Exhibits Cytolytic Activities

“…In the same way an interaction of CsTx-1 with the ion channel surrounding lipid layer is also thinkable. Such a case could be shown for GsMTx4, a specific inhibitor for pro-and eukaryotic stretch-activated mechanosensitive channels acting via bilayer tension (33,34). The neurotoxic activity of the ICK structure of CsTx-1 is then further synergistically assisted by the pore-forming activity of the peptide C-terminal ␣-helical part.…”