Characteristics of GsMTx4 That Enhance Its Potency Against SACs


Gsmtx4 is an amphiphilic peptide that inhibits mechanosensitive channels and was developed as a potential therapy for Duchenne muscular dystrophy (DMD). The peptide, derived from the spider venom of the Chilean rose tarantula Grammostola spatulate, has six inhibitory cysteine knots and two specific loop folds. This article, published in the Journal of Biological Chemistry, identifies features of the structure that enhance its potency against stretch-activated potassium channel (SAC) arrhythmias and reveals a mechanism for how this effect is potentiated in the presence of K+.

The authors designed short peptides, mimicking the inhibitory cysteine knot and loop regions of GsMTx4, to identify factors that enhance its inhibitory effects against SACs. They used a recombinant human SA big potassium channel (SAKcaC) as an example to test their approach. All peptides tested reduced the channel Po in patches at resting voltages. However, a single peptide, K25E, showed strong inhibition of both tetrads and quadruplexes of the channel.

Molecular Dynamics Simulations suggest that the positive charge of GsMTx4 is critical for membrane insertion and lipid displacement, but the authors also found that its high lysine content contributed to its high water-air partitioning in unstressed lipid bilayers. In fact, the Cs-1 plot of WT GsMTx4 shows a shallow compression slope, near the monolayer-bilayer equivalence pressure (pB) for peptides with high lysine content.

The CD spectra of the WT and all the K-E analogs were similar in solution, with the exception of a sharp negative peak at 228 nm for all analogs compared to WT GsMTx4. This was removed when the peptides bound to negatively charged POPG-POPC lipid vesicles, where they formed complexes with two acyl chains that stabilized the secondary structure. The spectrum reverted to that of WT GsMTx4 when unbound.


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